Powder, Velocities & Pressure

Help Support Muzzle Loading Forum:

nkbj

Cannon
MLF Supporter
Joined
Jan 31, 2009
Messages
6,960
Reaction score
296
If a powder gives low velocities relative to the same volume of other powders does that mean the pressures are lower?
 

dave951

40 Cal
Joined
Feb 27, 2019
Messages
390
Reaction score
259
Not necessarily but in general, yes. Murky answer. Lots of factors can affect velocity.
 

nkbj

Cannon
MLF Supporter
Joined
Jan 31, 2009
Messages
6,960
Reaction score
296
The question could obviously only apply with all else being equal except the powder itself.
And even at that, I suspect that a fine enough granulation could indeed drive up pressures without a definable increase in velocity when the barrel is long enough. I say long enough because if the barrel is short enough a spread in velocities will be obvious.

And if you look at it from another angle, low quality powder burns slower producing lower velocities which would allow the use of heavier charges producing a more gradual acceleration of heavier bullets, which in a longer barrel could be put to good use to achieve higher velocities without pressures being driven up as high as faster burning higher quality powders...
That's theory I may have to test out paper patching in the 38" long .52 bore.:rolleyes:
 

Loyalist Dave

Cannon
MLF Supporter
Joined
Nov 22, 2011
Messages
8,995
Reaction score
1,666
Location
People's Republic of Maryland
The question could obviously only apply with all else being equal except the powder itself.
And even at that, I suspect that a fine enough granulation could indeed drive up pressures without a definable increase in velocity when the barrel is long enough. I say long enough because if the barrel is short enough a spread in velocities will be obvious.
Yes I think perhaps "severely equal" would be the key...,
Because the breech pressure from the powder load at ignition would be influenced by the volume of the chamber formed when the ball is seated against the powder, and by how quickly that ball begins to move forward thus enlarging the space between it and the breechplug face and reducing the pressure, no?

LD
 

nkbj

Cannon
MLF Supporter
Joined
Jan 31, 2009
Messages
6,960
Reaction score
296
If a powder is low enough in quality then it would burn more slowly. Being a slower burning powder it could give the bullet a higher exit velocity in a longer barrel...
Wouldn't that be fun to test!
Perhaps Jacks Battle versus Goex FFg and FFFg and a 400 to 450 grain bullet in the .458 bore, finding out how much of each powder gave the same velocity. Never bothered to chrono very many loads but building a set of tables for this could be a lot of fun as well as instructive.
 

Carbon 6

75 Cal.
Joined
Nov 2, 2018
Messages
5,426
Reaction score
2,297
If a powder gives low velocities relative to the same volume of other powders does that mean the pressures are lower?
Yes, "if the powder gives low velocities". You've assumed the answer.

But the question remains, " why ?"
 

Carbon 6

75 Cal.
Joined
Nov 2, 2018
Messages
5,426
Reaction score
2,297
If a powder is low enough in quality then it would burn more slowly.
yes.
Being a slower burning powder it could give the bullet a higher exit velocity in a longer barrel...
It could but only under certain circumstances. and that is not likely.


Perhaps Jacks Battle versus Goex FFg and FFFg and a 400 to 450 grain bullet in the .458 bore, finding out how much of each powder gave the same velocity.
Are you sure your test fits your question and vice versa ?
 

Ranch 13

40 Cal.
Joined
Jan 19, 2006
Messages
170
Reaction score
12
If you can get a copy of the Lyman Blackpowder handbook from the late 70's/early 80's, they include pressure and velocity data with each load for every projectile they made a mould for , in common guns from the Colt copies to the rifles and even some shotgun data. Interesting reading there. The two powders they used were the only ones available at the time Goex and Curtis and Harvey.
 

nkbj

Cannon
MLF Supporter
Joined
Jan 31, 2009
Messages
6,960
Reaction score
296
Yep, got it. My copy has the front cover shredded.
In 1981 Wampus was having a litter and looking for nesting material. I was out of town on business, the book smelled like me, she used it! I think she also attacked "The ABC's Of Reloading".
The data in that Lyman handbook is pretty interesting. If you go all through the velocity and trajectory tables comparing round ball sizes the flattest shooting comes out somewhere between .50 and .54.
In my last post was thinking about running the tests to see how much of which powders would bring the same velocity. I've got a whole tray of paper patched and .457" sized 425 grainers ready to go. Could use Jacks Battle, FFg and FFFg. Could stick a magspark on it as a control, run the experiment and plot the curves here at home in an afternoon.
Might have to make time for that.
 

Ranch 13

40 Cal.
Joined
Jan 19, 2006
Messages
170
Reaction score
12
Projects like that are always fun, and can produce some interesting results.
 

tenngun

Cannon
Joined
Jan 27, 2008
Messages
12,009
Reaction score
2,260
Location
Republic mo
yes.

It could but only under certain circumstances. and that is not likely.




Are you sure your test fits your question and vice versa ?
I think about increased charges and diminishing returns. 30 grains in a .44 colt design gun produces velocity in the 800fps range, and loads easy. At forty grains you may not be able to compress it enough to seat the ball, but you don’t increase the velocity.
Overload a rifle will give you lower velocities but higher pressure. I think you would have to do some hard science testing to get a real answer
 

rodwha

58 Cal.
Joined
Oct 2, 2011
Messages
2,631
Reaction score
139
Location
Lakeway, TX
I think about increased charges and diminishing returns. 30 grains in a .44 colt design gun produces velocity in the 800fps range, and loads easy. At forty grains you may not be able to compress it enough to seat the ball, but you don’t increase the velocity.
Overload a rifle will give you lower velocities but higher pressure. I think you would have to do some hard science testing to get a real answer
That all depends on the powder being used. Lyman’s handbook shows 30 grns of Pyrodex P and a .451” ball achieving 896 FPS. 3F Goex produces 794 FPS. The testing done by Cumpston and Bates in their Percussion Revolvers shows an 1860 with 30 grns of Pyrodex P and a .457” ball producing 904-931 FPS depending on use of a wad. 28 grns of P and a 200 grn Lee RN producer 967 FPS, and that’s with a much heavier projectile and 2 less grns of powder. In a NMA 28 grns of 3F Swiss and a .454” ball produced 959 FPS. 28 grns of P produced 966 FPS. 28 grns of 3F Swiss and a 180 grn bullet have 962 FPS. 22 grns of Swiss and a 190 grn bullet gave 785 FPS and 28 grns of Goex gave it 764 FPS. Mr Beliveau’s testing of the ROA showed 33 grns of 3F T7 got it well above 1000 FPS.

And loading more than 30 grns most certainly does increase the velocity. I’ve yet to see an instance where a max load didn’t produce more velocity, and I don’t mean by the trickle. For instance the Lyman book shows 35 grns of P brought it up 83 FPS. Goex increased 54 FPS.

It’s all in the powder we’re talking about. And it’s why I don’t bother with anemic powders. 35 grns of Goex produced only 220 ft/lbs. Pretty dismal for hunting. 35 grns of P produced 294 ft/lbs, or about what I consider to be minimal at best. 30 (weighs 33) grns of Olde E and a bullet put me in the standard .45 ACP levels of performance, and more to my liking for hunting.
 
Last edited:

tenngun

Cannon
Joined
Jan 27, 2008
Messages
12,009
Reaction score
2,260
Location
Republic mo
Yes you can get varied velocities and energies changing brands. What I was referring to in this case was a point where increasing the charge would not increase the velocity. In Lyman’s test large charges could slow velocities even while increased breech pressures.
 

rodwha

58 Cal.
Joined
Oct 2, 2011
Messages
2,631
Reaction score
139
Location
Lakeway, TX
Yes you can get varied velocities and energies changing brands. What I was referring to in this case was a point where increasing the charge would not increase the velocity. In Lyman’s test large charges could slow velocities even while increased breech pressures.
Id certainly need to see this for myself as not even once, and the performance of these guns has been something I’ve looked into a lot for years, have I seen a bump from 30 grns to a max in these revolvers hasn’t increased the velocity.
 

VADSLRAM

Pilgrim
Joined
Jul 24, 2012
Messages
32
Reaction score
15
The correct answer is definitely "it depends".
Depends on where you measure the pressure, depends on the grain size, and with open powder it even depends on relative humidity. To me the most important "depend" is grain size. If you have cannon grade it takes longer to completely burn than 4F. If the powder all burns before the bullet gets inches down the barrel the pressures will be much higher than if all the grains haven't completely burned before the bullet leaves the barrel.
To the extreme if you take two quantities of powder that when burned produce the same volume of gasses. One 1f BP and the other AL based flash powder. the BP could very well not get the bullet out of the barrel while the flash powder could burst the barrel. I make my own fireworks and that is one of the tricky calculations. Is the lift powder fast enough to get the shell high enough but slow enough not to burst the mortar tube. And is the burst charge fast enough to cleanly distribute the stars but slow enough to ignite all of them.
 

rodwha

58 Cal.
Joined
Oct 2, 2011
Messages
2,631
Reaction score
139
Location
Lakeway, TX
Yes you can get varied velocities and energies changing brands. What I was referring to in this case was a point where increasing the charge would not increase the velocity. In Lyman’s test large charges could slow velocities even while increased breech pressures.
I have looked high and low and cannot find even 1 example that shows the velocity does not increase. What am I missing? Where have you found all of these examples?
 

tenngun

Cannon
Joined
Jan 27, 2008
Messages
12,009
Reaction score
2,260
Location
Republic mo
Lyman testing shooting a 34 grain GO 3 f got avg of 953 lup of 7240, increased to 37 that was max fps was 960 but 7420 lup.
The increase produced 7 FPS,
At 31 grains avg velocity was 859, but 28 grains produced 882. Lup for 28 grains was 6320, while for 31 lup was 6500. Velocity went down while increasing lup.
The 25 grain charge was 868, that was faster then the 34 grain charge 859.
This was in a .44 8” barrel.
 

rodwha

58 Cal.
Joined
Oct 2, 2011
Messages
2,631
Reaction score
139
Location
Lakeway, TX
Lyman testing shooting a 34 grain GO 3 f got avg of 953 lup of 7240, increased to 37 that was max fps was 960 but 7420 lup.
The increase produced 7 FPS,
At 31 grains avg velocity was 859, but 28 grains produced 882. Lup for 28 grains was 6320, while for 31 lup was 6500. Velocity went down while increasing lup.
The 25 grain charge was 868, that was faster then the 34 grain charge 859.
This was in a .44 8” barrel.
Interesting. I’m guessing you must be using the first edition because my second edition doesn’t show that and is void of pressure data. In all 3 powders, including Goex, the velocity increased more than just a little. And what that book and another I have, along with data posted on forums and in videos all seem to say the same thing. I find it rather curious that the testing you have goes against what appears to be the norm. Here’s the page:

 
2

Latest posts

Top