FFG vs FFFG- weight versus volume and velocity

[rich pierce]

Seems to me that the same volume of a smaller grained powder would weight more, packing closer together.  Is this the case with FFG vs FFFG and could this account for part of the difference in velocity between volume-based loads of rifles with these 2 powders?  Are published and reported velocities voolume based or weighed charges?

[Fred_Dwyer]

Are published and reported velocities voolume based or weighed charges?

I sure wish they said; that always leaves me wondering myself.

In my readings on the subject of charge vs pressure vs velocity I found, "it ain't as simple as all that."
One firm thing that I've found is that velocity varies with the integral of the pressure curve. Or perhaps more clearly, it is not the peak pressure, it is an average of the pressure over time.
Look at these curves, they compare Fg and FFg and Trail Boss. The pressures go up 10% from Fg to FFg, and so do the velocities; the curves look roughly the same. (ignoring +2 grains FFg){volume basis adds 2 grains} http://www.assra.com/yabbfiles/Attachments/45_70_pressure2.jpeg
Look at the Trail Boss, the pressure is up 50% and the velocity drops; the curve is much shorter.
Even more extreme examples; roughly same velocities, roughly 2:1 peak pressures.
http://www.assra.com/yabbfiles/Attachments/45_70_pressure3.jpeg

Perhaps not answering your question directly but trying to shed a little light. Maybe it leads to understanding. This sort of explains the usage of the F grades in various calibers, a big weighty ball isn't gonna get up and go with the "smack" of a fine grained powder when the steady shove of coarser powder avoids the peak pressures and gets that ball going. Simplistically put, yes, but that seems a reasonable way to put it. I know, to us it all goes boom but when things are measured in microseconds I need to use some metaphors.

Thanks to the ASSRA forum.

[Herb]

Rich, Goex 3F is BULKIER than Goex 2F.  I just did a lot of experimenting to arrive at this discovery.  I made a measure from a .300 Wby Mag case.  The case alone did not hold 100 grains, so I soldered on  another neck, then filled that case, weighed the powder, and filed the neck back until it held 100 grains of Goex 2F.  I developed a  technique and carefully measured 12 cases full of powder, which averaged 100.6 grains.  Then I repeated with Goex 3F in that same measure and 10 charges weighed 97.08 grains.  Swiss 3F is also BULKIER than Swiss 2 and Swiss 1 1/2 powders, and those powders are a lot heavier than Goex.  Swiss 3F averaged 113.35 from this measure. The adjustable brass measures are unlikely to give you the weight of powder the volume mark indicates.  Successive "throws" or measures are likely to vary from 2 to 4 grains.  I had to make a measure for each brand and grade and weight of powder I wanted and can now measure very uniform weight charges for any powder I use.

[The other DWS]

My understanding is that since most/many versions of BP is hydroscopic and can absorb moisture from the environment, the powders moisture content at any given time can skew weights.  On the other hand, unless it is so wet that the granules break down, the volume measurements remain pretty consistent, even though the moisture content can cause the weight to vary.

This may just be passed down ML-lore that may or may not be accurate, especially with modern powder.

I know that most of the BPCR guys load by volume; as do the extreme long range BPC guys, and they are pretty obsessive about detail.  However there is the size/sensitivity factor, and a bigger bore/bigger powder charge rifle will be more tolerant of small variations that a small squirrel rifle

[rich pierce]

Guys, that is a LOT of good information.  I never would have guessed that 3F is more bulky.  The info on the pressure curves makes sense too.  I wonder if a slower rising curve also affects felt recoil or if we're not that sensitive.  Good points by all, burn rates, etc.  I especially have noticed that fine powder more easily turns to mud in the pan on wet days!

[Daryl]

That's quite interesting Herb. My GOEX measurements have usually shown the opposite, with 1 to 3gr. weight more 3F in any given measure, than 2F.

Like DWS says, current moisture content means a lot according to the actual weight.

My chronographed results are taken from weighed measures, ie: powder measures that are checked for accuracy in throwing a given weight of powder.

 

[hanshi]

One thing that might not be figured into the discussion is the fact that black powders ALREADY contain a % of moisture as part of the production process.  This moisture content can vary among brands and lots.  I'm not sure how this might figure into the measuring and performance of various grades but I don't see why it might not.

[Herb]

Roundball, I thought about my choice of a word.  Goex 3F is lighter than Goex 2F?  Whatever it is, a measure of 100 grains of Goex 2F holds only 97.08 grains of Goex 3F.  As for moisture, these are 25 pound bulk bags of Goex I bought at Ft Bridger Rendezvous, April 2009 lots, from Craig Kirkland, Bear River Powder (see his ad on page 52 of May-June 2012 Muzzleloader Magazine).  They have been stored together in one pound Goex cans so their moisture is the same.  I repeat, I had to make a measure for each brand and grade of powder for any weight amount.  The powders are different in volume for any weight.

[Herb]

Here are some of the Black Powder measures I made from centerfire rifle cases with the fired primer in place.  (The .45 Auto is a cap for the .270 or .30-06 cases, should I want to take measured charges to the range).  The three cases on the right are 7.63 x 53 rimmed, nice for that size.  You see that 3F, whether Swiss or Goex, is larger in volume than 2F for any weight.

[The other DWS]

"My chronographed results are taken from weighed measures, ie: powder measures that are checked for accuracy in throwing a given weight of powder."

Darryl, what do you use as a moisture content benchmark when comparing bp performance if you are loading by weight.  Or is the BC humidity always constant?
It may or may not make a difference,  I don't know if anyone has done studies of how moisture content changes  impacts the burning rate and the resulting velocity/power/accuracy. 

 I have heard/read for years that some of the old highly favored powders burned "moist"  so that their fouling was softer and made reloading with a PB a lot easier.   {ref: Ferguson's 100 shot (or some similar number) in the rain in England---of course everything there is a mite soggy)

[William Worth]

As to volume and bulk, I do know that if you take X amount of wood and start splitting it, it gains volume due to swell factor.  Just as if you dig a hole and try to put all of the dirt back in the hole, it won't all go bacj into the hole, you will have a mound when done. 

You've introduced air space into a previous solid.

[Standing Bear]

Hmmmm.  Was the location of the moon considered?  I remember old timers saying that if the moon was over head when you dug a hole you couldn't get all the dirt back in but if the moon was under foot (over China) you couldn't fill the hole with the dirt dug from it.   

Never felt like doing that experiment.  Haven't seen evidence on targets that 2-3 gr difference in actual weight changed POI as long as all else was equal.  Also assuming .40 or larger caliber with nominal 50 gr or larger charges.
TC

[Dphariss]

There are a couple or reasons why an equal charge of FFF give more velocity than FF of the same powder, its related to burn rate.
But this is Mad Monk territory.

If the measure is properly made, pouring from a horn can be pretty accurate. But powder charge weight in a variable and if the shooter wants ACCURATE results from a chronograph then weighed charges must be used.
For example, from Mad Monk's data, 5 grains of powder can make as much as 110 fps difference in velocity in a 45 caliber RB rifle if its in the "sweet spot" for velocity gain. If 3 grains gave an increase of 40-70 fps it would cause a significant "blip" in the data.
So if doing a study with a chronograph or looking for 100 yard accuracy then its best to do at least the testing with weighed powder charges. THEN develop a measure design that matches the horn tip and develop a filling technique that gives a uniform charge weight for "loading from the pouch".
While its not as important with a RB rifle at 50-100 yards, 100 fps variation in velocity with a BP cartridge rifle makes the load useless over about 100-150 yards for precision shooting. At 300 variations of this magnitude can result in vertical dispersions of 30" +- in actual shooting at paper over a chronograph. This can occur simply by not using uniform compression of the powder charge.
This can occur in loading a ML by simply varying seating pressure.

Dan

[Daryl]

Spot-on, Dan- in my last chronograph session with the .40, I tested for and found 100fps change just from seating pressure, with the same load. That is why in all the video's I've compiled & when testing accuracy, I attempt to load exactly the same each time, putting the same pressure on the seating ball with the starter on top of the rod, giving it a whack with my palm to ensure it's on the powder and with the same pressure or compression ever time. This pays off in improved accuracy, especially at longer ranges.

Using this loading technique and mere stricken measure (usually no more than 1gr. total diff. in charge weight over 10 loads when tested) my shot to shot velocities are normally well under 20 fps. In the .58's and .69, they are normally under 8fps - when using a water based lube.

An oil or grease lube can double or more, the shot to shot variations.

The amount of velocity variations also have much to do with where in the charge weight spectrum, ie; "the sweet spot of velocity genation" as Dan put it, you are.

I load from a horn (small hole) and usually with the smallest diameter straight sided powder measure I can use for a given charge. The smaller diameter possible with straight sides gives me the closest or smallest variation load to load.  Sicne everyone has at least one powder measure, do a test yourself.  If you have a spout-cap for a powder can, the powder can is usable - if not, it is next to useless for loading from when testing as powder delivery into your "measure" will be too variable. Do a test and check it out- I did.  For most loads in .40 to 50 cal, a 3/8" diameter measure will provide good results.

DWS- I've not worried about moisture content - I leave that to the modern rifle bench rest shooters attempting to produce groups under .1" at 100 yards. For some of them, it's important.

I also make power measures/chargers, from ctg. brass.

[Daryl]

I just re-did a test using my two large horns - the 3f 1 pound capacity horn has a 1/4" hole, while the 2f 1 1/2 pound capacity horn has a .350" hole.
I used the same straight sided measure I just made for the .58 - which, when I made it, threw 'around' 100gr. 2F- close enough for the DR.

I attempted to pour the charge into the measure the same each time, back pouring to get the top surface of the powder more or less level and the same.  I was quite surprised as this measure and method of pouring charges reversed what I had 'tested' prior when using a 1 pound can with a .223 case soldered to a cap, for the spout. Perhaps this was due to the smaller measure only 3/8" ID or that the extra small diameter fo the neck of the .223 case restricted the speed of filling the measure with each powder, causing polar opposite results from today's testing.  For whatever these results are worth:
As you can see, my results are somewhat different than Herb's. One can only assume different 'batches' or 'Lots' of powder. That may also be why my results were opposite when tested similarly, some years ago. This GOEX powder, both 3f and 2f was purchased last Fall.

2F -
102.1gr.; 101.6gr.; 101.3gr.; 101.1gr.; 101.8gr.

3F -
93.7gr.; 94.0gr.; 93.2gr.; 93.5gr.; 94.1gr.

This measure was made from a .375 Remington Ultra Mag case having over 1/2" inside diameter, yet as you can see when poured from a relatively small opening on the horn, the pouring accuracy was fairly good at 1gr. for 2F and 9/10's gr. for 3F - but- only over 5 pours each. This could increase another .5gr. or even more, over 10 or 20 pours, I'd expect.  I didn't scrape the powder off the top of the measure making it perfectly flat, which would have made the 'pour's' a bit more accurate than what I got.

I used a normal powder beam scale for measuring.

[Daryl]

Testing one's own powder would be the only way to know for sure as to moisture - the humidity when poured into cans, method of pouring and subsequent storage would all change what the powder would end up as for moisture content.  Another change lot to lot, or mfg'r to mfg'r, would be the density of the powder granuals, along with any difference in grain/granual size.

 

[Daryl]

Don't know about you, but I usually purchase powder in a 25 pound plastic bag. When pouring the powder from that bag into a 5 pound coffee container, then from that in to old cans that have been sitting on the shelf the powder is subject to changes in moisture, depending on the day of the 'pour'. I guess I didn't explain it well enough - when I mentioned  pouring it into cans.

Then - there's the powder supply guy who buys powder by the bag from a GOEX supplier and buys empty cans from GOEX and fills them himself - at what humidity level? - you get to mark them as to granulation as GOEX leaves that up to the supplier in some instances - maybe all, I don't know.  That is how I received the last 5 pounds I picked up from a Rendezvous & I got to mark them with a 2F in felt pen.  The cans were not marked as to granulation as I received them.

[hanshi]

And that "sweet spot" speaks loud and clear sometimes.  For my .40 that magical spot was the span from 35grns to 40grns, just a 5 grain spread.  That 5 grains increased velocity by 229fps and the sd dropped to 5.  This was all volume measured loads with nothing weighed.  I used 3F & .390" ball.

For my .45 (.440" ball) the sweet spot occurred between 60grns and 70grns (didn't try 65grns).  The vel increase was 207fps for 1737 fps and sd of 17.

Of course more testing is required and I'll be getting around to it over the spring/summer.

[rich pierce]

You guys should have been scientists!

[Herb]

Well, some of us are, or were.  Or at least use the scientific method.

[Herb]

Here are the results of the weight-calibrated measures in comparing Goex 3F to Goex 2F.  This is my Jacob Wigle (Westmoreland Co. PA) .40 flintlock I built, with a 44" 15/16" Rice barrel, 50 yards from rest.  I used 40 grains as kind of a standard, 55 because someone said that worked well, 70 grains for the same reason, 80 grains of Goex 3F because Don Getz said it worked well in someone's rifle, and 90 grains of Goex 2F, I don't remember why. I had a damp cleaning patch on the jag as I seated each ball, thus wiping the bore as I seated the ball.   Cleaned the bore after the 3F series.  You can hold down CONTROL on your computer and hit the + key, and that will enlarge the image. Control 0 (zero) to return to normal.  Same ball, patches and lube here.   I don't know why some loads shoot badly and some shoot well.   If graphed, these load increases produce almost a straight line rate of velocity increase.

[Daryl]

Target 7's a peach, Herb- my own 48" twist .40 preferred 75gr. 2f GOEX, with a .400" ball using a .019" pocket drill patch.

[Mad Monk]

Testing one's own powder would be the only way to know for sure as to moisture - the humidity when poured into cans, method of pouring and subsequent storage would all change what the powder would end up as for moisture content.  Another change lot to lot, or mfg'r to mfg'r, would be the density of the powder granuals, along with any difference in grain/granual size.

 

From my work on checking moisture content of the various powders.

Moisture in the powder from the cans bought in the gunshop ran around 0.25% to about 0.50%.

Most powder manufacturers go by a maximum of 1.0% moisture.

They all now use a fairly good grade of potassium nitrate so hygroscopic properties are no longer a problem as they once were.

The quality/purity of the potassium nitrate used in the powder is the primary factor in how the powder will respond to Relative Humidity in the air around it.
With a good grade of potassium nitrate the powder is not prone to picking up moisture from the air until the R.H. reaches above 90%.

Moisture effect on powder burn rates does not come into play until the moisture content of the powder exceeds 1.0%.  Then you begin to see a slowing of the burn rate.

E. Ogre

[Herb]

Thanks, Daryl.  I'll try 75 grains of Goex 2F next time I shoot.

[Daryl]

Except for that one flyer, it's pretty good. I, however noticed the velocity spreads are a bit high.  I would try using a slightly undersized measure, and after filling, tap it 3 or 4 times to setting the powder, then top it off again, to get a more consistant weight.  Just a thought.