Thoughts on "load inertia"

[northmn]

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:


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.

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.

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

I thought I mentioned that the smaller bores also do not gain at the same rate because they have a higher surface area to mass ratio than a mid size bore and may start too easily.
My point was also that round ball shooters do not have all the variables that a BPC has.
I just dug out my copy of "Muzzle Loading Shooting and Winning with the Champions"  Copyright 1973.   BPC is a relative newcomer in popularity to the BP sports as far as press coverage anyway.  The big matches did not exist in 1973, and yet a great deal of research had already been done on PRB accuracy by that time. Some common comments in the book were that for match shooting one needs to use a ladle for casting more consistant round balls. Weigh the ball within .3 of one grain, Patch thickness and ball fit are critical to accuracy.  One used a mallet to seat his ball.  Keep a note book for what works and what works on some days as in temp.  FIRE A FOULING SHOT.  Do not load so tight you deform the ball too much, use false muzzles and lapped barrels.  A comment was made about barrel types, including choked ones and the fact that with proper load development they all work.  Another about working out so you can lift bench rifles to the bench.
My point is that a lot of work has already been done over a generation ago.  Many of the "new" ideas have been tried, and wheel reinvented.  Can the picket bullet experimentation help PRB shooting.  It may.  There have been a few technological developments since then such as teflon coated patches.  But a lot of what we take for granted has been used and proven on the range.  
As to foulings effect on velocity.  When I chronographed several different loads a while back and posted them, I found that without exception, the first shots were lower velocity than the succeeding shots, even when wiping between shots.  The most consistant velocities in my 3 rifles tried came after one or two shots and no wiping.  Daryl has also mentioned that he has noticed this.  Note the use of a fouling shot in my previous comments from bench/buffalo shooters.
Another point is that to really ring out the patched round ball in percussion, one has to start with a rifle built around a 1 1/8 inch barrel in 50 or 54.  These were the most popular rifles back then and I am willing to bet still are.  Most of out "rules of thumb"  revolve around a group of calibers in the 40-54 class.  Larger bores and smaller bores start to follow different rules due to dimensional shifts such as the scaler effect.

DP    

[northmn]

I guess to clarify, the PRB shooting sports have been established for some time with considerable research already in place.  Blacksmoke makes good barrels judging by his pictures of groups.  They will not shave off an inch from other barrels because there is no longer an inch to shave off.  Any developments will be small refinements of what is already in place.  While it is true that it is ridiculous to think that experiments with picket bullets or whatever may not be able to add anything, it is also arrogance to assume that anything earthshaking can be added to a refined and established sport.  If PRB shooting has any limitations it is in the fact that the events are commonly held at 50 and 100 yards.  It is possible that stretching the ranges, say 200, like suggested, would be more likely to wring out their capabilities.  50 yards is a pistol range. 

DP

[Dan]

Any developments will be small refinements of what is already in place.  While it is true that it is ridiculous to think that experiments with picket bullets or whatever may not be able to add anything, it is also arrogance to assume that anything earthshaking can be added to a refined and established sport. 

DP

I don't recall anyone implying that earthshaking things would come from this and do not see anything wrong with small refinements.  Your thoughts seem broad ranging on the subject.  If you have knowledge of specific research on this topic I would welcome direction.  I am admittedly less well versed on the subject of PRB rifles than a great many folks that post here, but on the matter of ballistics I am reasonably educated.  Dphariss has raised a question pertaining to internal ballistics that appears worthy of examination and it deals with a very specific aspect of load management with muzzle loaders using PRBs. 

While it is true that it is ridiculous to think that experiments with picket bullets or whatever may not be able to add anything

In context of the discussion, would you be so kind as to describe what congruent elements might be found in picket bullets and PRBs.  Honest question....standing by here.

Dan the Other

[tg]

Sounds like a lot of neat scientific stuff, but personaly I just pour in the powder drop in some hornets nest or a wad, then a ball then another wad or more nest. I haven't a clue where the inertia goes or if I ever had any...
I never saw any on any of the deer , squirrels or other game I shot so maybe I didn't have any, but things worked out ok anyway.so I must not have needed any.

[northmn]

I made reference to a book over 30 years old that pointed out the fact that the subject has been "researched" by serious competitors.  Dpharsis could very easily with his knowledge construct and know how to build a PRB rifle that could shoot X-rings.  That type of shooting is not popular on this web site as most have TG's attitude.  I do not think I have seen anyone, since I have viewed the website, build or showoff, a halfstock rifle with a match grade barrel at 1 1/8 inches, 50-54 caliber, 35 inches long, with a top grade percusiion lock and triggers.  If you really want to get into it you build it around an inline or underhammer action to put more weight in the barrel.  That is the specs for light bench or an X sticks guns weighing under 14 pounds.  Add a false muzzle.  The loads are ball diameters at bore diameter or even slightly over (for heavy powder charges) and a heavy patch.  Mallet loaded.  Personally, while I have thought about building one, I would not have much use for it, because like TG, I just want to enjoy my shooting at a much less restrictive level.  The biggest restriction on PRB is the ball itself as the wind plays hob with it and it does not retain velocity well.  Picket bullets and other bullets replaced the round ball because they are quite simply, more efficient ballistically.  The developments in BPC have been toward using a very heavy pointed bullet.

DP

[Dan]

OK, thinking here I'm seeing a difference in perspective on what this is about.  As I understand the topic, there is a question about load/charge variables specific to velocity extreme spreads and standard deviation.  Furthermore, the question goes directly to those aspects defined as load inertia. These things are related to accuracy for sure, but review of targets, regardless of range will shed little light on what's going on in the south end of the barrel.  By the time a bullet or ball exits the muzzle differences in internal dynamics will promote variations in barrel harmonics and increase dispersion.  One may infer consistency based on target analysis but there is no way to weight the random influence of wind or projectile variations...or gnats. Therefore, the conclusions reached by target analysis may or may not be valid.

There is a method of load development often used for white powder shooters called the Ladder Method, that being wholly focused on barrel harmonics and the identification of vibration nodes in the barrel.  I would suspect that long barreled muzzle loaders are very much affected by this issue.  I would also point out that minimum SD is not a guarantee of small dispersion.  My point goes back to something stated in one of my earlier posts on this topic; that it is necessary to segregate the variables to properly analyze them in a statistical sense.  What comes out of it may well be a grab bag of information of small value, but one never knows until they  explore.

Barring published reference on the specific point raised in this thread, I would necessarily conclude it does not exist.  I've read more than a few books on the subject of black powder guns  and seen no direct reference to the subject.  I have seen a lot of commentary that dances around the subject, but nothing to indicate specific focus.   Most discussion that comes close relates to conical bullets. I certainly understand the reasons behind picket and conical bullet development, but for every possible basis of internal ballistic comparison to PRBs, I see fundamental ballistic science basis to object to the comparison.  My imagination is somewhat limited though...

Admittedly, I have not made it all the way through the Warner-Lowe letters, but I'm working on it. 

Dan the Semi-Ignorant

[hanshi]

Yes it does make sense.  Colt tapered the bore on their exquisite Python revolver and probably others as well.  No one ever accused the Python of being inaccurate.   

[Dphariss]

I made reference to a book over 30 years old that pointed out the fact that the subject has been "researched" by serious competitors.  Dpharsis could very easily with his knowledge construct and know how to build a PRB rifle that could shoot X-rings.  That type of shooting is not popular on this web site as most have TG's attitude.  I do not think I have seen anyone, since I have viewed the website, build or showoff, a halfstock rifle with a match grade barrel at 1 1/8 inches, 50-54 caliber, 35 inches long, with a top grade percusiion lock and triggers.  If you really want to get into it you build it around an inline or underhammer action to put more weight in the barrel.  That is the specs for light bench or an X sticks guns weighing under 14 pounds.  Add a false muzzle.  The loads are ball diameters at bore diameter or even slightly over (for heavy powder charges) and a heavy patch.  Mallet loaded.  Personally, while I have thought about building one, I would not have much use for it, because like TG, I just want to enjoy my shooting at a much less restrictive level.  The biggest restriction on PRB is the ball itself as the wind plays hob with it and it does not retain velocity well.  Picket bullets and other bullets replaced the round ball because they are quite simply, more efficient ballistically.  The developments in BPC have been toward using a very heavy pointed bullet.

DP

The BPCR "technology" was basically lost when Dupont destroyed the powder industry in the US circa 1900 and blackpowder primers disappeared about WW-I when the makers essentially doubled the amount of compound in all the primers. This last REALLY hurt.
The primer change alone destroyed accuracy for shooters like Harry Pope and they only go it back by using smokeless in some manner. So BP disappeared in the cartridge world for any serious shooting. We lost the "link" to the old target shooters and much of what was available was for schuetzen shooting and no longer worked without using smokeless.
It was so bad that at least one pretty big name in shooting stated that accuracy with BP loaded cartridges was impossible. Not only did we not know how, one key component, a "soft" primer, had not even been made for about 60-70 years.
We had a few books and such and more have since come to light. But one of the "light bulb" moments for me was reading Rywells book with the Sharps catalog reprints. An old catalog reprint told how to load shells and it WORKED.
Eventually I was telling people that they needed to forget 75%, or more, or what they "knew" about smokeless reloading to load for BPCR. Some "laws" for successful smokeless reloading often do not apply and are sometimes 180 degrees out.

MLs on the other hand never completely died. The loss of powder makers did not effect them as much, the "primers" did not change. People were still shooting MLs the old way. What a 1980s a new to ML shooter could draw on NMLRA matches/experience that had been running for decades. When I started in the mid 1960s I could learn the basics, good info, by reading Muzzle Blasts. A greenhorn could load a rifle with about 1/2 ball weight of powder +-, a .005-.010"under ball, a heavy patch with almost any lube and it will shoot pretty well if the barrel is OK.
When serious BPCR competition came into being we had a lot of competitors, good shots with decent rifles, who were loading ammo that would not hit the backstop every shot at 300 yards, the easy target in silhouette.


Other things.
The conical, the Minie and picket bullet certainly did not universally replace the RB in hunting rifles. The picket especially took over for long range and a lot of target work in the 1830s-40s. But the extra powder and lead needed, the exacting process and the tools generally needed made them a little too complex for the average squirrel hunter. The Minie was easy to load but was prone to sliding off the powder and was very limited as to its velocity due to its large hollow base, it was unsuitable for subsistence hunting. The slug gun evolved but was more impractical for general use than the picket.

Elongated projectiles do upset and fill the bore as Mann wrote in "The Bullets Flight". In fact Mann believed the lead bullet was to easy to deform at higher pressures. The PP bullets used in slug guns and BPCRs  *must* do so failure to upset will blow the patch. I have shot cylindrical PP/GG bullets that were near or under *bore* diameter for their full length in both ML and BPCR and they work fine and do not gas cut. This is how the various "naked" modern ML bullets work.

"Reinventing the wheel". A lot of this has gone on since, in some cases, the "wheel" had been lost. Yes some have even rewritten history to sell products or for other reasons and not just concerning projectiles.

Yes, this may be "too scientific". But suspect that everyone here is using their rifle/gun in a manner that was figured out by someone who was "too scientific". Some "rifle crank" will post something here and it goes into everyone's "data" base when they read it. I learned how to make a smooth rifle shoot better here and other things. Like paper cartridges for rifles etc etc.

I HATE doing serious load development anymore. Its not "fun" to me. But it must be done from time to time.
Now I need to seriously "develop" the trim in a closet.... Before my wife gets home
Dan

[Daryl]

I also believe that if given a place expand laterally they will. 

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.

Now THAT seems to make a lot of sense...

Yes - this is, as it happens and why choked barrels usually show slightly better accuracy than non-choked.  I proved this to myself back in the mid 70's when I was in the sport only a few years.  A constant taper I'm not sure of, though - at least with a lot of difference between groove AND bore diameters, muzzle back to breech in both borer and grooves.
My own Military Replica barrel with a tapered groove diameter of about .006 to .008" difference or so, doesn't burn patches in the least, yet ball with patch having been swaged to a maximum diameter of .580" at the muzzle when seating, become quite loose in the breech's groove diameter, where the measurement is perhaps .596" groove to groove - yet - there is no burning of the patch - indicating there must be some obturation due to the inertia factor.  Note, in this barrel, the bore's diameter remains constant and only the grooves have tapered depth, from .003" at the muzzle to .011" at the breach.   Although it is designed for easily expanding conicals with hollow bases, it shoots exceptionally well with patched round balls (which it shouldn't) and with solid pure lead slugs which also appear to fill the grooves just fine upon discharge.  Loading and shooting 10 rounds of slugs, then a tightly patched round ball shows no difficulty in loading.  if there was no obturating in this bore, solid lead slugs would lead the bore due to the fire blasting past, melting off lead and spraying the molten lead into the bore ahead of the bullet, which then irons it into the bore when it passes.  With patched balls, no obturation would burn the patch and perhaps even lead the bore as well - yet - no leading, no burnt up patches and great accuracy with both.  

There is probably a gradual scale of ball weights/sizes where obturation does take place due to the resistance to movement solely due to mass of the ball - as noted in previous posts. This is reasonable and shows common sense.  Obturation of the bullet is due to the level of pressure in concert with the alloy of the ball or bullet. This is common knowledge amongst cast bullet shooters and there is a formula which will show at which pressure, different alloys will obturate as the pressure overcomes their resistance due to their compostion.  I seem to recall WW allow requires something in the realm of 24,000PSI before it will expand - and this is with bullets.  The formula does not take into consideration the mass of the projectile nor the size - it is simply mathematical - at "X" pressure, there will be obturation - below that pressure, there will be none.  It is entirely possible my common sense is in error and math proves to be correct.

I realize this post is in lay-terms, but I obtain a better understanding using examples of the topic which show pictures. Yeah - compared to others in this thread, I lack their scientific knowledge and verbage in posting, but do understand the posts and their content - I think? - (yes- a question)

[Dan]

Obturation pressure = 1440 X BHN

http://www.sixguns.com/crew/obturation.htm

[Daryl]

Thanks Dan - that's it.

[northmn]

I mentioned a Green River Barrel that did not seem to want to shoot.  They were choked and I think that was the problem as I remember it started shooting well at 140 grains (it was a 58).  The ball needed that to obturate is what I am now thinking from reading these posts.  It also liked a very thick patch and a 575 ball.  I did not like what it seemed to like so I sold it.

DP

[Daryl]

Mine also DP.  At 140gr. it shot incredibly well, but then, my other .58's also preferred 120gr. and up.  Even though mine was a heavy gun, that narrow Hawken guard was just too oncomfortable for me to keep the rifle. Any position other than offhand was murder.  On an English-styled gun, the same caliber with 140gr. would have been a moderately heavy load only- nothing to write home about.  The obtruation deal might have been a part of this.  Smaller calibers create much heavier pressures with seemingly"light loads- in comparrison.
I-too used a .575" ball and a .022" denim patch - same with all my .58's that had a .580" bore.

[Dphariss]

The problem with the "obturation pressure" thing is that smokeless is seldom fast enough. I KNOW for example that in a 44-40 FFG Goex (IIRC) will make more pressure in the CYLINDER than Unique will at 7-8 grains, though the smokeless will produce equal or higher velocity with a barrel installed. Shooting a SA Colt with no barrel in the frame can be VERY enlightening.
The pressure curve and initial acceleration is just wrong to bump lead bullets before gas cutting occurs.  Smokeless at 45 colt pressures does not make the pressure at the right TIME to prevent gas cutting if it EVER does.
A 45 Colt with WW alloy and 231 powder, 7.1 gr  (factory dup load). Simply will not bump up in the cylinder with a 250-260 gr bullet NO MATTER THE ALLOY. One SAA 45 Colt I had, a Cavalry Comm. had a .457-.458 cylinder throat. It gas cut to beat the band with smokeless and .452-.454 bullets. Also leaded the barrel. Finding an old Keith mould that threw oversized bullets cured the gas cutting but the .451 bore leaded beyond  the forcing cone. It shot wonderfully for about 4-6 shots then went to the level of the gas cut bullets there simply was no work around other than jacketed bullets which at least did not lead, still shot like $#@*. So I sold it to a Cavary Re-enactor (the wagon driver that got "stuck" while crossing the river in "Dances With Wolves") and he of course was thrilled.
However, I had a 38-40 Colt with 400 cylinder throats and it would bump the bullet in the *forcing cone* with 7+- grains of 231 and fill the .405 bore, but sometimes the rifling would be longer on one side than the other on recovered bullets....
So far as the heavier bullets being faster than the lighter ones on the website linked above. I wonder if the researchers thought of the idea that maybe the heavier bullet raised the *pressure* a little. Since they were using the same powder charge it HAD to. So I consider this little write up just about useless based on my experience with numerous 45 colt 38-40 and 44-40 revolvers. Also in my experience if the bullet gas cuts it leads at a wonderful rate so if the bullets were gas cutting they would have known it. Had they looked at recovered bullets for gas cutting it might have bolstered their argument. But I figure in that many 45 Colt revolvers they had to have 1 or 2 at least with OS cylinder throats that are probably gas cutting everything they shoot. But they might be really lucky in this regard.
Funny thing is BP WILL bump bullets smokeless will NOT when loaded to the same velocity+-. It also will not gas cut since they obturate  just as the bullet starts to move. BEFORE it leaves the cartridge case.
Yes, I suppose that certain smokeless powders will reliably "bump up" bullets. I just don't know of any.

Those who doubt me should try shooting .457 bullets in a TD Springfield, Sharps etc with a .464+ bore and see if they can make it shoot with smokeless.

Dan

[Dan]

Dan,

The formula referenced is, in my opinion, one of those "rules of thumb" that has floated around for some time.  I have no idea who contrived it, but there are certainly aspects of obturation not addressed, such as sectional density.  There is little doubt in my mind that regardless of firearm, powder or charge, conicals will obturate more at a given pressure than PRBs.  Logically, those bullets with high sectional density and thus large inertia will obturate more.  My own experience with BP and smokeless in rifles seems to be consistent with the formula.  My single foray with smokeless and paper patched bullets in a RSB did as well, but they were full house loads...as in bring the earplugs Mabel.  Shot quite well too.  With that said, I don't believe anyone here doubts that Lord Black will cause obturation.

The question we consider then is just what circumstances contribute to load inertia in PRB rifles, and I accept without deep consideration that obturation is a factor of substantial note.  There is a question in my mind as to what degree a round ball will obturate and if heavier charges have a linear or geometric influence. It would seem to me, and this is a guess, that several strings  registered over a chrony and using increasingly hard alloys would reveal some of this.  I also guess that the effect might be more dramatic in a tapered bore rather than straight.  Don't know this is a legitimate approach but I would think two rifles, one with taper, one without, fired in a series of strings in two paths might do it.  One would use BHN 5 lead with incremental increases in charge while the second would use a constant charge with incremental increases in BHN, say 5, 12, 20?  One or the other, or both, will at some point indicate a trend of reduced or increased velocity standard deviation I think.

There is an article in the recent edition of BPC News regarding the .25-20 SS by Herr Garbe.  Now this may or may not be meaningful in context of our discussion, but it occurs that perhaps it is.  The point he made went to reduced SDs resulting from charge compression AND the milder small pistol primers.  He wondered aloud about the causes of case stretching resulting from hot primers and uncompressed loads as well.  Well, I'm not that much of a CSI, maybe it's relevant, perhaps not.    You and Mr. Pletcher have indicated reduced SD in BP arms resulting from compression as well, even with muzzle loaders and contrivances to impart same on his part, and drop tubes on yours.  Well, maybe there's something in all that worthy of further discussion. Until you had mentioned that, the idea of using a drop tube on my rifles had never crossed my mind. The idea of using my calibrated hammer (my right palm) had.

By the way, there is also an article in the same issue regarding the relative brisance of different brands of primer caps for muzzle loaders...and a few regular types as well if I recall correctly.  With pictures!

Stray thoughts from a troubled mind.

[Dphariss]

To my mind there is no consistent way to reduce the velocity variations in a PRB rifle short of compression and perhaps a drop tube or cleaning every shot or using water based lubes or all three.
Fouling is not going to be consistent enough.
In shooting my 54 at 200 a few times I found that ANY feeling of roughness due to fouling caused accuracy problems. So I started dry brushing and damp patching.
I also found that seating the ball flush with the muzzle and cutting the patch there gave better accuracy.
NONE of these things were apparent at 50-100 or I did not NOTICE them. A key point.
The 200 yard groups never showed vertical stringing when loaded this way so I assumed the consistency was good.
I think that PRBs with their low sectional density upset minimally. I feel they "probably" upset just enough the make things work a little better. The problem is in proving it. Its pretty easy in a bulleted gun. A 457125 (govt 45 500 gr  bullet) cast soft will upset all the way to the ogive in a ML bore that is .008+ over size. The land marks on the bore rifling nose were not full depth but well pressed in. Alloy was very soft, but this was 30 years ago +- .
A 45 PRB is NOT going to do this. For one thing I believe the patch supports the ball to some extent and if the fit is tight there may be no upset at all.
Larger balls might upset more but I don't think its enough to do more than perhaps tighten the fit slightly and improve accuracy. I suspect a thousandth or 2 at the most.
Getting proof is not going to be easy.
For those that would try to do this the oiled sawdust trap is described in Mann's "The Bullets Flight" pg 59 of my Wolfe Publishing edition. The instructions are longer than I want to type but fine hardwood sawdust was used, it was oiled to the point of saturation but not dripping. It should not clump. They sifted the sawdust to make it uniform.  It takes a LOT of oil and for PRB I suspect that 12x12x36 box will be needed to stop the bullet. The front would likely need to be very light cloth. With heavy loads the box would need to be shot at 75-100 yards to reduce chances of expansion.
They used light machine oil but I suspect that 5w or 0W30 etc motor oil or light hydraulic oil/"tractor transmission oil" from Wally World would work OK. Oils that might gum up should be avoided.

Dan

[Dan]

I have the book and will ponder your thoughts...as I review some other information.  I have seen photos of PRBs just clear of the muzzle that were obviously deformed in consistent fashion with obturation. Don't recall the caliber though.   My gut says any support offered by the patch will extend only to the point the material is fully compressed and that is a variable black hole.  The earlier testimony about tapered bore rifles shooting better with heavy charges indicates PRBs do obturate...in my opinion.

Clean barrels are uniform certainly.  I'm puzzling about ways to play with fouling in a uniform way from shot to shot that does not require surgical cleanliness. 

[northmn]

I read in a BPC publication that using BP one should not consider a 45 70 a Short in a longer chamber like a 45 by 2 7/8 as it upsets to the chamber and then has to be resized hitting the bore.  Some use them that way with smokeless but they stated it should not be done with BP.  Maybe the little bit RBs upset is why pure lead is more accurate.  In a good barrel, by the time the patch ball combo reaches the breech after a long push one tends to notice a little easier seating unless the bottom area gets fouled.  It would not take a lot of upset to refit the tight fit to the bore. A cartridge has a press fit of bullet to case that also helps pressure build.  Consider that if we would make a pressure gauge on a ramrod and seat the ball (or bullet) in a ML, would we maybe not get a "bounce back" as the fit is no longer tight enough to maintain the pressure and have at best uneven resistance?  This would especially be true in a choked barrel.

DP

[Daryl]

Dpharris- I believe your last post pretty much says it, in regards to obturation of a round ball and the amount thereof. There is no argument about the expansion of elongated projectiles - even short ones like the REAL bullet or short picket bullets. Sectional Density certainly helps.  It is interesting, the amount of powder needed to obtain good accuracy with the pickets ( low SD) - example in .40 cal. picket 80gr. powder.  The shorter the projectile, the greater must be the pressure to obtain obturation. Carry this to what we see as the extreme - the round ball.

 Now, enter the rifled Foster slug as loaded in factory shotshells is pure lead, lighter than the same size in round ball, so it should be less prone to obturation - however, due to the hard wad support beneath,  it's very thin skirts like a 'Minnie' ball & and very fast burning, fast pressure rising shotshell powders used today, this slug obturates to fill even .730" bores, presssing the rifling out flat in some bores and even to  complete obliteration of the grooves. This I've seen and tested myself. RP slugs did the same, even though they were much smaller back in the 80's, when they were a mere .690" in diameter, expanding out to a full .725", the size of my double's bores.(tight 12). So - some smokeless work to obturation in a similar fashion to BP due to an extremely fast pressure rise in the LARGE bore, whereas most smokeless powders don't.

Obturate is the correct word - Pocket Oxford- stop up, seal,(orifice in body, breech of gun) - obturation-noun;  obturator-noun; obturating-applicance-noun.

Obdurate, as I've seen in books on muzzleloading explaining what happens to the ball upon ignition, instead of obturation - obdurate -adjective - hardened, stubborn;  obduracy-noun

[Daryl]

DP - you have a good point - that the patched round ball will not maintain pressure and is easily moved.
 Failure to lift the hammer to 1/2 bent postion and remove the cap from the nipple in a cap gun, causes an air compression between the patched round ball and nipple/cap seal that causes difficulty in pressing the ball down and also causes the ball to rise back up the bore if the presssure is not released by the removal of the cap or lifting the hammer to 1/2 bent. 

[longcruise]

If pressure is applied to a round ball thus;



Then how can it be expected to "bump up"?

[Dphariss]

If pressure is applied to a round ball thus;


Then how can it be expected to "bump up"?

Its the initial acceleration that causes the ball to deform, assuming it does very much. The pressure just causes the the acceleration which, if fast enough, moves the back faster than the front and causes the projectile to deform.

In digging balls out of back stops I can say that the marks put on the ball by the lands look no different than one started in the muzzle and then pulled back out. But its impossible to measure a ball shot into any surface that will cause it to deform on impact.
This is why the oiled sawdust thing would be great.
Now an undersized bullet such as a 500 gr 45 will show obvious signs of complete upset to fill the bore.
The patched bullet is a little harder to read.  I would love to see what e of the 40 caliber pickets looks like as it clear the muzzle but they do not survive back stops well at all.

Dan

[Daryl]

Dan, Dan, Dan, Dan - your fit is much too loose & the pressure arrows coming from outside the bore! - just kidding.  It is a graphic reminder of how the pressure actually is present in pushing on the entrie base of the ball as well as inwards on the bottom ogive.  We know from research, that boattailed jacketed bullets are tougher on bores and throats than are flat based bulles, due to the powder gasses exerting pressure against the angles of the base, being directed up the slope towards the fit into the gooves and perhaps bouncing back against the bore itself.

 The fact remains boattailed bullets are tougher on bores and actually obturate less than does a flat based bullet. Perhaps the same re-direction of powder gasses happens to the patched round ball or picket bullet's rounded base, however one might think no patch could survive if that did happen, yet the patches most certainly do.  What gives?

The more I think about this, the less I think obturation actually takes place with round balls, yet why do some people's drop-the-patched-ball down-the-barrel seem to shoot OK, without obturation happening at least slightly?  Now, 'seem to shoot OK' might need clarification as  a lot of different people have different ideas on what OK accuracy actually is.  Perhaps even some re-inactors think their loads are accurate  as did the fellow shooting .30/30 cases full of sand.

I would think the tighter the ball is held in the bore by the patch, the more the powder charge must manifest itself to get that 'tight' ball moving, yet such balls are very easily pulled when a, shall I say it, dry ball occurs leaving one to think a badly fouled bore actually grips the ball harder than does one just cleaned by a tight fitting combination being seated. And no - no hammer or mallet is needed - a starter is handy & makes loading quicker.

[Dan]

Its the initial acceleration that causes the ball to deform, assuming it does very much. The pressure just causes the the acceleration which, if fast enough, moves the back faster than the front and causes the projectile to deform.

I agree with that.

I do not believe your diagram is properly representative of the pressure acting on the ball.  The pressure, or force vector, would properly be depicted in context of its action perpendicular to the cross sectional area of the ball and parallel to the bore, vector oriented toward the muzzle. The way it is depicted in the diagram would lead one to believe there is force applied on the ball, perpendicular to the bore, or close to it.

I have a fairly busy schedule over the next two months but after mid June I will have some time to play with this.  I see a sawdust and oil box in my future.

If anyone wants to set procedures let me know what you think appropriate....purpose being an attempt to quantify PRB obturation...in a .45 cal. flintlock, straight bore.  I have pure lead balls, .440 and .445" and patches ranging from .005 to .025". Anyone having moulds that will cast alloy to the same dimensions and can establish BHN, I'll run with that too.  

After some thought on the matter I withdraw the picket rifle from the endeavor because I ain't got a clue how to measure diameter on a ball shot through odd number grooves.

[northmn]

Daryl's comments on the boat tail also indicate a round ball may have more problem obturating unless really driven with a heavy charge.  Also consider that for ML's the Minnie bullet was quite a breaktrough for the military.  The Lee Hollow base bullet is popular for old Springfield 45-70's with their varying bore dimensions.  When one looks at the target shooters use of lapped barrels we also see another variable in the picture.  Lapping is done to try to get the bore even in diameter, they polish out and try to eliminate tight spots.  A bullet of what ever design will resize to the narrowest part of the bore.  Musket shooters also have determined that a Minnie is not all that inaccurate if it slightly engages the lands as compared to the sloppy military fit.

DP