Author Topic: Thoughts on "load inertia"  (Read 31357 times)

Offline Dphariss

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Thoughts on "load inertia"
« on: April 18, 2009, 05:05:35 PM »
This was originally a response to one of Daryl's posts on "No Cone" but decided it was straying from the original topic so I started a new one.

Ball fits.....

I have often wondered, as I gained in knowledge, if FFFG does not shoot better in some guns because it bumps the ball somewhat and this gives a tighter fit. This is something difficult to measure  though I suppose the old oiled sawdust bullet trap might work if placed at 100 yards to let the ball slow before impact.
I know that in HEAVY bullets even FG will produce a lot of upset in the bullet. Soft bullets over 1.2 long will upset as much as .010 over the full length of the bullet.
Even a slight upset on a ball could aid the fit.
In looking at Lyman's shadow photos of RBs we see one shot with a heavy charge of powder that is flattened somewhat at the nose. I believe they state its air resistance that caused this but it is entirely possible that is was done during initial acceleration.
I also believe that heavy charges tend to seal the bore better under initial acceleration since there is powder pressed against the ball.  I know that in BPCRs the lack of a over powder wad will produce very well defined powder grain impressions on the bullet base so the powder is still granulated when high pressure is put on the bullet.
There is a difference of opinion among shooters as to grain size. I see powders such as FFG, at least in the slower grinds, as too slow for the RB in most calibers.  Mostly due to the balls low inertia and the fact that it does not have to forced into the rifling when it is fired. Then there is bullet fit in the cartridge case which can produce considerable initial resistance. All these thing increase load inertia and allow the powder to work more efficiently. The RB rifle has none of this. I a bore that is clean or with the fouling softened by the patch lube there is far less inertia and since the ball moves so much easier the efficiency is reduced.
I believe inertia is why larger caliber rifles get usable velocity with lower ratios of powder to ball weight as a result of this.
Now we get into fouling effecting ball movement. Shot with a lube that does not remove the fouling from the lands the increased "load inertia" of a fouled bore, the grip the fouling will produce on the ball, will cause velocity to INCREASE every shot. At least to as many as I shoot over a chronograph.
This could be why a clean bore seems to be more important at longer ranges than at close ranges since the effect of velocity variations increases with range.

Just some things to consider.
Gotta run.
Dan
« Last Edit: April 18, 2009, 06:49:52 PM by Dphariss »
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Offline hanshi

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Re: Thoughts on "load inertia"
« Reply #1 on: April 18, 2009, 06:25:16 PM »
In thinking about your post, Dan, I believe you may be on to something.  The patch thread pattern is frequently found on the base of PRB and that would require a bit of "bump".  Interesting to find out what others have found.
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Offline Dan

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Re: Thoughts on "load inertia"
« Reply #2 on: April 18, 2009, 09:17:45 PM »
Dan, I don't recall the text verbiage in the Lyman Manual and am too lazy at the moment to dig it out.  Air resistance cannot be the cause of flattening of the ball you reference in the photo, but obturation (bump up) certainly will occur and result in such deformation.  Obturation results when pressure is applied by the charge and inertia causes resistance to acceleration of the bullet or ball.  A simple comparison would be to toss a lead ball in the air and whack it with a ball bat.  If you can find it after the fact it will be oblate in form.  Force and inertia at work again.  I don't know if there is an outer limit on how much obturation can occur...it's a computation of pressure, alloy and mass inertia.  More pressure will engender more complete obturation to the point the bore dimensions allow it to occur.  Dr. Mann got into this in his book and it is, as I understand it, the source of slumping in conical bullets. More lead and/or more powder equals more pressure.

The reference you give to powder grain impressions on BPCR bullets, I'm not so sure about.  This may occur during the firing or loading if compression is used to seat the ball or bullet, assuming soft alloys of course. I have found this to occur with lead over smokeless too, but the observation comes from loads that are compressed.

I won't dispute your thoughts on fouling effects, making a fair bit of sense to me and all that.  An increase of frictional resistance would logically increase pressure but I don't think that relates to inertia.

A fellow named Crowley discussed powder granulation and twists in a 1976 article in Muzzle Blasts.  His spin was faster powder for slower twists and slower for faster etc. He was a BP bench gun builder and competitor, maybe you know of him.  I don't recall he addressed the theory in his article, just referencing experience.  Me, well, I cannot render valid judgment based on experience.  My little picket rifle with the .38 bore and round balls shoots noticeably better with 1-1/2f Swiss than 3f Goex, which may support his idea as the rifle has a 38" twist, even if it defies conventional wisdom....or my wisdom anyway.

Dan the Other

Offline Dphariss

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Re: Thoughts on "load inertia"
« Reply #3 on: April 18, 2009, 10:24:15 PM »
Dan, I don't recall the text verbiage in the Lyman Manual and am too lazy at the moment to dig it out.  Air resistance cannot be the cause of flattening of the ball you reference in the photo, but obturation (bump up) certainly will occur and result in such deformation.  Obturation results when pressure is applied by the charge and inertia causes resistance to acceleration of the bullet or ball.  A simple comparison would be to toss a lead ball in the air and whack it with a ball bat.  If you can find it after the fact it will be oblate in form.  Force and inertia at work again.  I don't know if there is an outer limit on how much obturation can occur...it's a computation of pressure, alloy and mass inertia.  More pressure will engender more complete obturation to the point the bore dimensions allow it to occur.  Dr. Mann got into this in his book and it is, as I understand it, the source of slumping in conical bullets. More lead and/or more powder equals more pressure.

The reference you give to powder grain impressions on BPCR bullets, I'm not so sure about.  This may occur during the firing or loading if compression is used to seat the ball or bullet, assuming soft alloys of course. I have found this to occur with lead over smokeless too, but the observation comes from loads that are compressed.

I won't dispute your thoughts on fouling effects, making a fair bit of sense to me and all that.  An increase of frictional resistance would logically increase pressure but I don't think that relates to inertia.

A fellow named Crowley discussed powder granulation and twists in a 1976 article in Muzzle Blasts.  His spin was faster powder for slower twists and slower for faster etc. He was a BP bench gun builder and competitor, maybe you know of him.  I don't recall he addressed the theory in his article, just referencing experience.  Me, well, I cannot render valid judgment based on experience.  My little picket rifle with the .38 bore and round balls shoots noticeably better with 1-1/2f Swiss than 3f Goex, which may support his idea as the rifle has a 38" twist, even if it defies conventional wisdom....or my wisdom anyway.

Dan the Other

You miss the point, "load inertia" is different than the inertia of the bullet which is fixed by its weight. "Load inertia" is what occurs when bullet are loaded with a high bullet pull in the case, seated hard on the rifling, the powder charge is heavily compressed OR the PRB is held in place by fouling. It effectively increases the bullets inertia by making it harder to move.
Increasing the load inertia UNIFORMLY for each shot will almost always REDUCE the velocity SD.
But with the PRB it is impossible to be uniform concerning fouling in the bore. Now this can effect things in several ways. The grooves may be partly filled with fouling and this may reduce any blowby that might be occurring and increase the velocity. Of it may be the ball being jammed into fouling on the lands or a little of both.
So far as the bullet base dimples. I try to load ammo so that the bullet is just in contact with the wad or powder when seated. If the powder is to be compressed it is done in a separate operation since drop tubed powder is hard to compress very much and doing so with the bullet will tend to "swell" the nose so that bore riding noses will not chamber.

I am sure Lyman states that the air pressure or shock wave has flattened the balls nose. But the book is out of reach.
Dan
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Offline RobertS

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Re: Thoughts on "load inertia"
« Reply #4 on: April 19, 2009, 02:21:44 AM »
I can't contribute anything to the discussion, but it's something to ponder.  Could the impressions in the base of the bullet, assumed to be the imprints of powder granules, actually be craters from the explosion of those granules located closest to the base?  That may almost be the same thing, but seems more likely in my small mind.  Either way, it's something new to me.

Offline Dan

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Re: Thoughts on "load inertia"
« Reply #5 on: April 19, 2009, 02:43:04 AM »
Quote
You miss the point, "load inertia" is different than the inertia of the bullet which is fixed by its weight. "Load inertia" is what occurs when bullet are loaded with a high bullet pull in the case, seated hard on the rifling, the powder charge is heavily compressed OR the PRB is held in place by fouling. It effectively increases the bullets inertia by making it harder to move.
Increasing the load inertia UNIFORMLY for each shot will almost always REDUCE the velocity SD.
But with the PRB it is impossible to be uniform concerning fouling in the bore. Now this can effect things in several ways. The grooves may be partly filled with fouling and this may reduce any blowby that might be occurring and increase the velocity. Of it may be the ball being jammed into fouling on the lands or a little of both.
So far as the bullet base dimples. I try to load ammo so that the bullet is just in contact with the wad or powder when seated. If the powder is to be compressed it is done in a separate operation since drop tubed powder is hard to compress very much and doing so with the bullet will tend to "swell" the nose so that bore riding noses will not chamber.

I am sure Lyman states that the air pressure or shock wave has flattened the balls nose. But the book is out of reach.
Dan

OK, there was a conceptual fork in the road and I took a left turn.  Was looking specifically at the word "inertia" in the sense of physics, not in the sense of "effective increase" thereof.  On the point of reduced velocity SD, it makes sense that it would and I think it one of reasons factories crimp their ammo.  A crimp is an easier method of regulating neck tension that most any technique one might dream up.  Not the best, but it provides statistical envelopes that are practical.  The bullet engaged in the lands would do the same, but not to the same degree.  Contrary to conventional wisdom, doing this does not raise peak pressure as much as the use of different primers in cartridge guns, and that includes jacketed bullets.  In context of muzzle loaders and round balls, I think what you bring up has validity, but the variables in regulating it are vast.  So we wipe....

I have a very high regard for Lyman and generally recommend their load manuals to neophytes first and foremost.  That said, if they report air pressure or sonic shock waves the cause of deformation in the photo you mention, they are wrong.  Now I gotta go find the danged thing and find out...... :(

Offline longcruise

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Re: Thoughts on "load inertia"
« Reply #6 on: April 19, 2009, 05:52:08 AM »
Quote
The reference you give to powder grain impressions on BPCR bullets, I'm not so sure about.  This may occur during the firing or loading if compression is used to seat the ball or bullet, assuming soft alloys of course.

I think Dphariss is on the right track with the pressure idea.  I have observed those same powder granule impressions in BPC loads put together as dan describes with no seating pressure.  But, the clincher for me is that I've observed those same impressions on the base of MaxiBalls loaded with only typical ram rod pressure in a .50 cal gun.

Quote
In thinking about your post, Dan, I believe you may be on to something.  The patch thread pattern is frequently found on the base of PRB and that would require a bit of "bump".

I've observed that too.  Here's a pic of one;



But, notice that the weave is impressed around the complete base of the ball, most of which is showing since the ball was flattened on impact.  So, if the pressure is applied all around the ball to impress the weave, then it would have to be applied all around the ball for the purposes of bumping the ball up.  Sooo, how do we bump it up if we are squeezing it evenly from all sides toward the center of the ball?

Quote
A simple comparison would be to toss a lead ball in the air and whack it with a ball bat.  If you can find it after the fact it will be oblate in form.  Force and inertia at work again.

Yes, but what if we could cut a perfect half ball round depression in the bat and hit the ball with such accuracy (precision? ???) that the ball was perfectly placed in the depression when it was hit.  Now what would the shape of the ball be?

When we mix comparisons of conical bullet behaviour and round ball behaviour under pressure we are comparing two entirely different things.
Mike Lee

Offline Dan

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Re: Thoughts on "load inertia"
« Reply #7 on: April 19, 2009, 06:36:25 AM »
Dan,

I dug out the book, and your recollection is correct.  Deformation is attributed to the shock wave. 

I stand by my earlier objection to that premise.

I should have said in my last that mechanical or interference restrictions to bullet movement have influence on powder burn.  Consistency in initial movement of the ball/bullet as might be plotted on the pressure curve would logically reduce SD.

Dan the Other

Offline Dphariss

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Re: Thoughts on "load inertia"
« Reply #8 on: April 19, 2009, 07:01:43 AM »


OK, there was a conceptual fork in the road and I took a left turn.  Was looking specifically at the word "inertia" in the sense of physics, not in the sense of "effective increase" thereof.  On the point of reduced velocity SD, it makes sense that it would and I think it one of reasons factories crimp their ammo.  A crimp is an easier method of regulating neck tension that most any technique one might dream up.  Not the best, but it provides statistical envelopes that are practical.  The bullet engaged in the lands would do the same, but not to the same degree.  Contrary to conventional wisdom, doing this does not raise peak pressure as much as the use of different primers in cartridge guns, and that includes jacketed bullets.  In context of muzzle loaders and round balls, I think what you bring up has validity, but the variables in regulating it are vast.  So we wipe....

I have a very high regard for Lyman and generally recommend their load manuals to neophytes first and foremost.  That said, if they report air pressure or sonic shock waves the cause of deformation in the photo you mention, they are wrong.  Now I gotta go find the danged thing and find out...... :(

Note this was written while you were posting your finding of the photo.
But will post anyway.

A friend of mine laid "load inertia" on me sometime back but its a perfect description so I use it too. Saves a lot of words.
Pg 167 of the 1975 copyright edition of their "Blackpowder Handbook"
.
"Fig. 9 Shadowgraph of a .445 RB at 2220 fps Velocity. Note the flattening of the ball by the pressure behind the shockwave."

Looking at it I think its distortion of the shadowgraph by the shockwave or ?. I have not looked at this photo in years and took it at face value years ago.

The problem with crimp is that it more often than not hurts accuracy. Lead bullets especially soft ones don't like being pushed though  a crimp. But sometimes it helps. BPCRs can be horribly individualistic especially when different reamers are used even for the same cartridge.
BP is far different that smokeless in cartridges. A gap much larger than .010 between case length and chamber length will often result in lead or paper rings at the case mouth as the powder bumps the bullet before it starts to move.
The BPCR shooters work load inertia in various ways, some use no neck tension at all and generally use some bandaid approach like very heavy compression but its not a good answer IMO.
Little of this is applicable to MLs. But ML arms do benefit from drop tubes but they are only practical as range accessories at matches.
Some shooters report heavy compression in MLs helping with accuracy but there is no way to get much compression on powder by hand, some mechanical advantage is needed to produce more than 1/8" of compression on drop tubed powder charges. Yes, I have actually tested this with a arbor press with a scale to measure handle pressure and a cartridge case with a false bottom in a chambered chunk of barrel. Crude perhaps its still informative.
While most ML charges are not properly drop tubed, the powder is generally poured too fast and the inside of the barrel is not smooth which could also effect compaction as well. Properly drop tubed powder, especially Swiss is pretty hard to compress. The PSI at the punch face gets pretty high once past about 5/16-3/8". Compression is WAY past "pushing on a rod" pressure at about 1/8 to 3/16. So I do not consider compressing the powder practical in a ML.
Properly drop tubed (cartridge loading) is poured at a consistent rate for each cartridge taking perhaps 5 seconds for the typical charge of powder. Pouring too fast greatly reduces compaction. Some shooters vibrate the cases.
Uniform compaction via drop tube or vibration, allows a uniform compression of the charge for a uniform seating depth. It also produces more uniform ballistics, so uniform that the SD gets down to the accuracy error of chronographs. It also greatly reduced fouling in the bore.
Why? *Probably* due to the way the flame propagates in the charge.
So careful drop tubing is surely a good idea in MLs and this is confirmed by its use by ML slug gun and picket rifle shooters.
It really helps (from reliable "rifle cranks")  though I have not tried it personally. The tube must end about 1/2" above the highest level of the powder in the bore to be effective.

Note than many straight case BPCR shoot best with NO compression at all. But without compression transporting the ammo will cause vertical dispersion problems so about 1/16" or a little less is recommended. I used to use 1/8 for BN cases with GOEX.

In some testing, limited, I found the lubing the bore after cleaning seems to help my experimental picket rifle's accuracy. But this is not set in stone.
I suspect it will shoot as well or better with 1.5 Swiss as FFG. So far best groups have been 80 grs of FFG  Swiss in a 40 with a 132-135 grain swaged FP, FB picket. But its still nothing to right home about, probably 2-3" at 100. 70 grain group is much bigger.
Why the picket takes so much powder I have no idea but it seems to be fairly typical.
This is a 48" twist and perhaps the twist needs more powder.
But then Chapman tells of using 2" of powder in the bore for a 38 picket rifle with a gain twist and if IIRC it ends in the 30s twist range. Would have to re-read to be sure.
He indicates that hot powders do not work as well with the picket.

Sorry about all the BRCR content but there has been a lot more serious shooting done with BPCRs over the past 20 years than with PRBs. Lots of shooters shoot a LOT with sophisticated sights at ranges to 1000 yards and even beyond. There is a measured mile match in Northern Wyoming and some people are VERY serious about this. Then we have the Schuetzen shooters who try to shoot 250s at 200 yards and the 25 ring is not all that big.... The level of development is pretty darned impressive. But they are still having problems beating some of the old records.
We have people doing a lot of very good work with MLs to but the numbers are not as high.  Few ML shooters chrono all their target work as well as shooting for group. It is amazing what can be learned with one of these speed meters. Some pretty heavy BPCR shooters are buying ML picket and slug guns and shooting these as well. Some of these were ML shooters who, like me, drifted to BPCRs. It was a living and shooting 200-1000 yards is a lot of fun. But BPCR is also a lot of work and I shudder at detailed load development these days. To much stress ::)
Hope this makes sense.
Dan
 

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Offline Blacksmoke

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Re: Thoughts on "load inertia"
« Reply #9 on: April 19, 2009, 07:40:13 AM »
Dphariss--- I cannot speak from a lot of  experience in the realm of conical bullet ballistics.  However in the realm of PRB ballistics it is another matter.  I do not have a chronograph but I have and use a so called "proofing bench" for testing the integral accuracy of muzzle loading gun barrels. So I think you are on to something here! It has been a longtime belief of mine that soft round lead  balls do indeed obdurate when subjected to the blast of exploding black powder that is placed behind them. Perhaps not with the same amount lateral tension as a conical but never the less they will have the same tendency to upset.  I also believe that if given a place expand laterally they will.  Since a patched round ball is being loaded from the muzzle ,the patch and ball are squeezed to the specific dia. of the bore being loaded and the rifling is then "engraved" onto the soft lead ball through the patch. As the load is forced down to the breech the projectile stays the same dia. as when it was first loaded in the muzzle. Now if that soft lead ball had a slightly larger surrounding  at the breech than the muzzle, when it "bumps up" it will, in effect, be re engraved as it travels towards the muzzle.  Thus providing a tighter grip on the PRB by the lands all the way to the muzzle. What I am talking about here is a tapered bore.   My tests on the proofing bench showed that a tapered bore produced better groups than a parallel bore.  Of course that is why I taper my bores before I rifle them--.004-.006" larger at the breech than the muzzle. This concept is not a new one it was under stood and practised many decades before I started rifling barrels--- Bill Large for one, and I believe that the Hawken boys did similar things to their bores on the famous "Hawken" rifles.      Just something more to ponder.  :-\        Hugh Toenjes
« Last Edit: April 19, 2009, 07:45:30 AM by Blacksmoke »
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Leatherbelly

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Re: Thoughts on "load inertia"
« Reply #10 on: April 19, 2009, 03:11:29 PM »
  Interesting...Point and question,
    With consistent pouring of powder at the muzzle, doesn't the rifle barrel act as a drop tube? Perhaps a little more consistent with a smoothbore due to fact of being that,smooth bored as opposed to rifles.

Offline Dan

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Re: Thoughts on "load inertia"
« Reply #11 on: April 19, 2009, 04:41:36 PM »
Dan,

I am in agreement with your analysis of BPCR and lack of detailed analysis in the PRB reference internal ballistics.  It has the appearance of something Mr. Pletcher might shed some light on, no? (I love to volunteer other people ;D)

Having spent some time in study on the matter of exterior ballistics and Florida Statute, I am stricken by the propensity to divide these things into narrow focus elements for analysis.  I think it would work in this case if one if judicious.  To that end, we are in agreement that PRB and BPCR have little in common other than lead and powder.  I would argue that there is little in common between PRB rifles and slug guns, or picket rifles as well.  Ergo, time is best spent with sole attention to the issue at hand.

Given: 

1) One cannot compress BP in meaningful amounts with a ram rod.
2) Consistent compacting of BP contributes to reduction of velocity variations.  I differentiate "compression" from "compacting" in that one requires mechanical advantage while the other relies on minimizing airspace in the charge (drop tube).
3) There is advantage to be found in regulating the point in the pressure curve wherein the PRB begins to move. 
 a. The factors that influence which are within our direct control are, with all else equal,  ball diameter, patch material and thickness, alloy, charge quality and quantity,  lube efficiency and bore condition. (I likely left something out here, but it's a start.)
 b. A factor that has influence but is difficult to regulate to advantage is fouling. Fully cleaning the bore between shots is problematic and obviates perceived advantage to regulating load inertia.
c. For purposes of this discussion, "load inertia" is defined as those aspects of the charge (patch, powder and ball) which contribute to consistency and reduction of velocity variations.  They are mechanical in nature.  EX: interference fit between bore and charge. See paragraph 3a.


Find:

 Identify actions or aspects of this process which will contribute to ballistic consistency  and may be intentionally manipulated by the shooter with the single objective of increasing accuracy in PRB rifles.


Before we go further in this discussion, I would like review of the above in order to provide focus on the discussion.  There is no pride in the preceding text and it may be modified or beat to death at will, by one and all.  My desire is to pursue the investigation logically and perhaps answer a few questions along the way, or provide catalyst to analysis to specific elements which may not have been thoroughly addressed in years past...our past.  There are interesting points on the table... What say ye?

Daryl

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Re: Thoughts on "load inertia"
« Reply #12 on: April 19, 2009, 05:35:06 PM »
Most Interesting, and good thread, DanPhar - for those inclined toward the technical aspects of shooting.  I've got to pick Carol up for the Sunday shoot soon and will comment later when I've had some time to think about all the great posts so far. Thanks for the headaches to develop as I do this, guys.  Good stuff.

Hugh - no chronograph?- in this day and age - interesting. Gads, :o I thought everyone had a at least one chronograph. ;D  just fooling with you -  :-*

northmn

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Re: Thoughts on "load inertia"
« Reply #13 on: April 19, 2009, 07:02:32 PM »
I question the comment on the lack of work done on getting accurate loads in ML's and patched round balls as much as the fact that it has been done but due to the lack of variables has not been pursued as in elongated bullet work.  Part of the issue is in the nature of a round ball, where to get more weight you have to get a larger ball and the other part is the nature of the patch, ball combination for reloading.  At the ranges round ball loads are shot, chronographs do not mean much.  Accurate loads in a patched round ball are achieved by the use of a very tight (as in sometimes seated with a mallet) loads.  Some use ball diameters that are larger than the land to land diameter of the bore.  Also the larger bores at 50 and above seem to be the rule as they are the most accurate at longer ranges.  When I chronographed a few loads a while back I found that 2f gave considerably less shot to shot deviation than 3f in my 54.  This is generally accepted for larger bores.  Daryl has mentioned the use of 2f even in a 40 as being more consistant.  Another thing is that if one uses one half weight powder to ball weight as in 110 grains in a 54 to its 220 grain ball weight one sees a higher velocity with the smaller bores.  This is due simply to the scaler effect of spheres, where the surface area increases by the radius squared while the volume increases by the radius cubed.  There is less available surface area for the gases to push against per grain weight of the ball as the diameter increases.  A mention was once made that small bores also seem to lose effenciency, which may be explained by the fact that the surface areas is appreciably larger and the ball is accelerated easier permitting less pressure buildup.  Also powder granulation seems to be related to bore size in that 3f in a 32 may be roughly like 2f in a 50.  This "inertia" you are considering is the scaler effect.

DP

Offline Dan

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Re: Thoughts on "load inertia"
« Reply #14 on: April 19, 2009, 07:48:31 PM »
Northmn, I'm thinking its a relative comparison.  Cartridge guns are much more tractable in analysis than muzzle loaders so far as internal ballistics factors.  On another angle, PRB shooters are likely more prone to pragmatic lateral problem solving.  By that I mean they are looking for "good enough" and will change dimensions or components until it is good enough rather than the best. Determing what is "best" may be difficult with a flint lock in its own right. Doesn't describe all folks I know, but there are a great many variables in the process and by nature of the arms it is difficult to state definitively what results in what inside the bowels of a PRB gun.

An example of one variable is that of a tapered bore, as indicated by Blacksmoke.  With a chamber area of the barrel .004-.006" over muzzle diameter it is reasonable to conclude there is less consistent resistance to initial ball movement before the onset of obturation.  BP seems to generate greater velocity variation under such circumstances and in context of the discussion less load inertia.  I've found good accuracy with tapered bores in other arms, but see no basis to conclude one way or another that it is beneficial for PBR rifles.  Such might be resolved by analytical testing.

northmn

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Re: Thoughts on "load inertia"
« Reply #15 on: April 19, 2009, 08:15:07 PM »
Those that shoot the "rest" type matches such as X sticks, bench or even chunk, continue to experiment beyond good enough.  Here they use false muzzles and other loading aids.  Consider that a 45 BPC can use bullets ranging from 300 grains to 550 and you see a considerable range of variables in that alone. Generally the long range BPC use a 1-18 twist and a heavy 500 grain + bullet.  A PRB ML has ball diameter as a variable, but that is reasonably limited.  We have discussed ad nausium, twist rate for a ML and one would find that that will vary on a firing range, but many bench rest like a slower twist as they may use heavier charges to get the velocities up.  Patches vary from Teflon coated to regular patches.  Lubes are tried.   Basically I think you are selling the round ball shooters short by saying they do not test loads and experiment, its just that the game is a little different.  A flintlock by nature is going to give a more erratic ignition than a cap lock, and a cap lock a more erratic ignition than an enclosed catridge.  Consider that some have used enclosed nipples taking centerfire primers for ML competition.  Also inlines existed on the target ranges long before Knight came out with his contraptions, we called them zip guns.  People that compete at these levels are very analytical, but as in BPC, you will see different theories and those different theories win often enough so that conclusions may be difficult.   To see if Blacksmokes ideas will win, that type of barrel needs to be used in an appropriate configuration in these matches.  The precision of a hand lapped match barrel whether choked, tapered or straight is such that it takes a scope to test any differences and they will be very small as in fractions of an inch.

DP

Offline Dan

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Re: Thoughts on "load inertia"
« Reply #16 on: April 19, 2009, 11:20:10 PM »
Not selling anyone short, just looking at the vast amount of research on this subject... ::)

And I don't find the ancillary illustrations pertinent.

Offline Larry Pletcher

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Re: Thoughts on "load inertia"
« Reply #17 on: April 20, 2009, 07:05:42 AM »
I got in on this topic in pieces because of lack of time the past two days.  I just reread the topic and find it fasinating.  I'm not sure where this is headed but will follow it with great interest.  Has anyone played with a capture system-     oil-soaked -sawdust for instance? 

Steve Chapman and I have experimented with load compression and accuracy with RB but want to repeat the trials with another gun.  We began to see trends but were't satisfied with our control of variables.  What we did may not be relevant to the topic anyway.

Regards,
Pletch
Regards,
Pletch
blackpowdermag@gmail.com

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Offline Dphariss

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Re: Thoughts on "load inertia"
« Reply #18 on: April 20, 2009, 08:24:42 AM »
The problem with trying to use fouling to create load inertia is that its not consistent.
The constant increase in fouling causes an increase in velocity, at least in some cases.
I do not consider it as a way to gain so far as uniform ballistics.

Northmn:

"Another thing is that if one uses one half weight powder to ball weight as in 110 grains in a 54 to its 220 grain ball weight one sees a higher velocity with the smaller bores.  This is due simply to the scaler effect of spheres, where the surface area increases by the radius squared while the volume increases by the radius cubed.  There is less available surface area for the gases to push against per grain weight of the ball as the diameter increases."

If you check Lymans BP handbook you will find that 1/2 ball weight of FFFG powder in a .36 with a 32" barrel produces 1579 fps
A 32" barreled 50 with 90 grains FFFG makes 1891fps
My 16 bore rifle with a 30" Nock breech barrel makes 1600 with a 140 gr Swiss FFG and 1650 with 150 gr. With this ball weight (437) 150 is just over 1/3 ball weight.
A 50 will produce similar velocities with the same ratio of FFFG powder. According to Lyman.
The 36 makes 1335 with a similar ratio of FFFG.
If we change the 36 and 50 loads to FFG the velocity will fall off significantly.
Is this due to inertia of the larger ball or to the bore size allowing more of the charge to light faster I cannot say.  But remember the more you restrain BP  the more efficient it becomes. Be it in firearms or blasting rock.

So far as the BPCR experimentation. I did not intend to short change the RB shooters in the comments on the amount of experimentation being done.
But then one must remember that to really wring out a BPCR you, in theory at least, need to try at least 20 different primers alone. For example LR, LP, LRM, LPM and then the match primers and then the other brands. 10-15 rounds with each possible primer is going to be 200-300 rounds easily.
Then there are several brands of powder in various granulations, then bullet lubes, alloys, bullet designs, over powder wads.
Now with experience and the help of friends you might narrow the primers to 4 or 6 (maybe only 40-100 rounds testing primers) and not test the rest. We know that there are basically 3 lead alloys to try 1:20, 1:30, 1:40.  But I once had a bullet that would not shoot soft and needed #2 alloy (hard) alloy.
The RB rifle is not this complex. Maybe 4 different powders, 2-3 different ball sizes, then play with patches and lubes.
Then add in that every new lot of primers is another variable. Shooters would find a "good" lot primers  or of Goex and buy all they could because the next lot required them to start over with the primers, compression etc since it was different and groups went south with the new powder loaded like the old powder.

I started this thread to provoke thought and see what other experiences there were. Through this more experimentation is done, more people relate experiences and  we ALL learn.

Does EVERYONES rifle gain in velocity as it fouls??

Another thing about drop tubes. Some shooters did not want the bullet/ball running into powder grains adhering to the barrel as it was pushed down. They thought it would hurt accuracy.

The picket bullet is not a patched RB. But it uses the same patches and lubes and like the Kentucky rifle its an American original, or so  I read. Its is also a HC projectile from 1830 onward that saw wide spread use. Look at the Gumph marked bullet mould in Whiskers "Gunsmiths of Lancaster County" three different bullet shapes. The heavy slug gun is also an American inventions so far as I know and predates the American Civil War.
I further submit that thinking that the round ball shooter can gain nothing from the experiences of picket and slug shooters is just silly. Especially if you have percussion rifles.

Dan
He who dares not offend cannot be honest. Thomas Paine

Offline Dphariss

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Re: Thoughts on "load inertia"
« Reply #19 on: April 20, 2009, 08:26:05 AM »
I thought the above post was sent this AM and got back to the computer and its still setting there.
So its a few hours late ???

Dan
He who dares not offend cannot be honest. Thomas Paine

Offline Dphariss

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Re: Thoughts on "load inertia"
« Reply #20 on: April 20, 2009, 08:27:43 AM »
Northmn, I'm thinking its a relative comparison.  Cartridge guns are much more tractable in analysis than muzzle loaders so far as internal ballistics factors.  On another angle, PRB shooters are likely more prone to pragmatic lateral problem solving.  By that I mean they are looking for "good enough" and will change dimensions or components until it is good enough rather than the best. Determing what is "best" may be difficult with a flint lock in its own right. Doesn't describe all folks I know, but there are a great many variables in the process and by nature of the arms it is difficult to state definitively what results in what inside the bowels of a PRB gun.

An example of one variable is that of a tapered bore, as indicated by Blacksmoke.  With a chamber area of the barrel .004-.006" over muzzle diameter it is reasonable to conclude there is less consistent resistance to initial ball movement before the onset of obturation.  BP seems to generate greater velocity variation under such circumstances and in context of the discussion less load inertia.  I've found good accuracy with tapered bores in other arms, but see no basis to conclude one way or another that it is beneficial for PBR rifles.  Such might be resolved by analytical testing.

Choking a PRB barrel will often help the accuracy. it also helps ease the loading.

Dan
He who dares not offend cannot be honest. Thomas Paine

Offline Dan

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Re: Thoughts on "load inertia"
« Reply #21 on: April 20, 2009, 04:51:05 PM »
Well, I'm thinking.... ;D

In consideration of tapered bores, yes there are parallels between PBR rifles and the others but the variables cloud the analytical processes.  As an example, the physical dynamics are different between conicals and round balls due to inertia (the physics definition).  Conical bullets are likely more affected by obturation and that point is subject to variables based on charge weight and alloy. They use no patch, or in some cases, a thin paper patch and the differences in gas seal between conicals and PRBs is not clear to me.  How different patch material (paper/cloth) affect obturation is not clear to me. The higher sectional density of conicals would also contribute to greatly to the concept of load inertia and comparatively would moderate the effects of loose fit of the bullet in the early phase of the firing sequence.   I would opine that tapered bores would stand against the load inertia concept, even if they shoot well.  Therein is found a conundrum. 

The matter of using fouling to regulate load inertia was at first....messy on a conceptual basis, at least to my fuzzy brain.  After some thought I don't know that it is.  The objective is consistency first and foremost and secondarily perhaps to assist in containing the charge during ignition.  There is a parallel with the BP bench guns here, but I've seen no thorough analytical research on the point.  The slug gunners and BPCR shooters of today seem to have various pet methods which include blow tubes, a certain number of wipes with this and wipes with that, and of course humidity plays as does the type of lube.  One variable after another, and on top of that one of our current shooters with champion pedigree has stated that he doesn't give the process all the same energy and detail that he once did.  I fall back to my earlier statement of "good enough".  It is not necessary to clean the bore between shots, only to do so consistently and in incremental stages to examine this issue.  A chronograph will give the truth to the issue.

If the goal is to segregate those things which contribute to reduced standard deviations in PRB rifles it will be necessary to to test each individual component in depth with that specific variable.

What I think could come out of this is a collaboration amongst forum members to look into this.  I do think the "all else being equal" clause can be used appropriately and with exception of the tapered bore/straight bore analysis, each element can and should be done by one person and one gun, analyzing component variables such as primer caps, lube, etc etc.

I have at present, a flint lock of .45 caliber, and a .38 bore picket cap lock, both of which do well with round balls.  The picket has a choked muzzle, the flinter is straight of bore.  Two brands and two granulations of powder and 4 varieties of caps rest in waiting.  I can retrieve my Chrony quickly enough and am willing to explore this in concert with others here on the forum but do not have the time to do the whole banana.  If we want to pursue this, let the consensus develope as to who does what and what the issues are to be examined...then I will pitch in.  I think it would be an interesting collaboration for Muzzle Blasts. 


Offline Dan

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Re: Thoughts on "load inertia"
« Reply #22 on: April 20, 2009, 05:01:45 PM »
I got in on this topic in pieces because of lack of time the past two days.  I just reread the topic and find it fasinating.  I'm not sure where this is headed but will follow it with great interest.  Has anyone played with a capture system-     oil-soaked -sawdust for instance? 

Steve Chapman and I have experimented with load compression and accuracy with RB but want to repeat the trials with another gun.  We began to see trends but were't satisfied with our control of variables.  What we did may not be relevant to the topic anyway.

Regards,
Pletch

Larry,

I've been pondering the compression issue and while in agreement with Dan that PRB ML compression is problematic, it occurs that it might be possible to affect such with various contrivances such as a cam or lever assembly which clamps on the muzzle, and a steel rod.  Not practical for field work, but might get the job done for purposes of this inquiry.  Can you describe how you approached the problem?  I think it would be meaningful to pursue this but am uncertain of the application of findings after the fact.

Dan the Other

Offline Larry Pletcher

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Re: Thoughts on "load inertia"
« Reply #23 on: April 20, 2009, 07:45:44 PM »
Snipped . . . . Can you describe how you approached the problem?  I think it would be meaningful to pursue this but am uncertain of the application of findings after the fact.

Dan the Other

Dan,
Steve and I used a collar on a steel bench rod to control compression.  We moved the collar in 1/16" increments and measured compression in inches as the BPCR shooters do. 
We hurried the project along and now wished we would have changed a few things.  I wrote this up on a web page and our proceedures and changes for future testing are located there:

http://www.blackpowdermag.com/featured-articles/load-compression-and-accuracy.php

Our conclusion was that compression helped both flint and percussion rifles, but we want to redo the test with the changes noted.

Regards,
Pletch
Regards,
Pletch
blackpowdermag@gmail.com

He is no fool who gives up what he cannot keep to gain what can never be taken away.

Kayla Mueller - I didn't come here of my own accord, and I can't leave that way.  Whoever brought me here, will have to take me home.

Offline Dan

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Re: Thoughts on "load inertia"
« Reply #24 on: April 20, 2009, 09:24:43 PM »
Larry, thanks for that.  Noticed a chronograph in one of the pictures, do you still have the velocity information?