School me regarding burn rate and barrel length.

Pond, James Pond · June 28, 2013, 04:33 AM

I've recently come to the likely conclusion that I may want to revisit my powder choices.

For my 4" .44 Mag, N110 has yielded some good results, and I can use is with relative confidence as my Lyman's manual also provides data for a 4" barrel: nice to know figures I get are based on a similar firearm to theirs.

Not so with my snub. I am not finding a sweet spot for my 2" barrel using my mid burn-rate powder.

So I started thinking and that got me tied up in knots.

My logic:
If a slower powder is good because it keeps the pressure wave in the barrel building, it stands that this is most desirable in a longer barrel.
Conversely, it then stands that a faster powder will give the most velocity from a shorter barrel, without wasting gases in a nuke-sized muzzle flare.

But will it give more velocity or less or the same as a slower powder in that same barrel?

Just because a slower burning powder charge has not all burnt up in the barrel, it doesn't mean that it won't already have built up respectable velocities.
A faster powder's combustion will occur within the barrel length, but that does not mean it will generate more velocity in the time taken for the bullet to leave said barrel.

And so now I find my logic starts chasing its own tail....

So what is the rule of thumb?

jim8115 · June 28, 2013, 09:47 AM

Been playing around with power pistol in 357 Magnum. I am finding that it really shines if you are loading for a short barrel.

158 cast 8.0 PP
1103 FPS from a 2 1/2" 686 , 1226 from a ruger 6"GP100 a loss of about 10%

158 Nosler JHP 8.0 PP
1030 from 2 1/2 , 1160 from 6" -11%

For comparison
13.5 #9
1024 from the 2 1/2" , 1296 from the 6 " -23%

Especially interesting, 8.0 PP actually outperforms the #9 load in the 2 1/2"

Don'tkillbill · June 28, 2013, 01:03 PM

I really like 296 in my 357 magnum loads up to 20 grains with the 125 grain bullets. The 158 grain is better as it engages the rifling with more surface area. I shoot out of a 1892 and a 586. I get a little more speed out of the
16 inch barrel.

Bill

Pond, James Pond · June 28, 2013, 03:29 PM

Does this mean that, as a rule, the shorter the barrel, the faster the powder needed?

jim8115 · June 28, 2013, 08:58 PM

"Does this mean that, as a rule, the shorter the barrel, the faster the powder needed? "

Well, it means that you will likely get better results with a somewhat faster powder from a short barrel.

Now, there are those that will flat out tell you" if its faster in a long barrel, it will be faster in a short barrel". They are simply wrong. There may be exceptions, I dont know, because I havent tested every powder. But I have done tesing with h-110, #9, etc, comparing them to unique and power pistol.
As a general rule, with 158 grain bullets anyway, I have found best results with faster powders in 2- 21/2 inch barrels.
I think some folks think the huge recol and blast always = more velocity. A chronograph will prove this wrong

JIM

wncchester · June 29, 2013, 08:29 PM

"Now, there are those that will flat out tell you" if its faster in a long barrel, it will be faster in a short barrel". They are simply wrong."

I'll flat out tell you that's simply wrong. Pressure in a handgun typically peaks in about 2-3" of bullet travel (some 3-5" in rifles). Velocity is totally dependant on the total pressure:time curve driving the bullet, not the peak pressure. Of course the ideal charge in a longer barrel will always be "faster" because the bullet will continue to accellerate as long as it's under pressure but the curve itself is what determines the best volocity at the moment of exit for any barrel length.

For 'normal' barrel lengths (i.e., longer than maybe 1/2"), using a faster than optimum powder simply peaks and falls off too rapidly for best velocity no matter the barrel's length. Thus, whatever charge provides the optimum pressure curve for a given bullet in a given fire arm is independant of the barrel length.

June 28, 2013, 04:33 AM	#1
Pond, James Pond Senior Member Join Date: July 12, 2011 Location: Top of the Baltic stack Posts: 6,079	School me regarding burn rate and barrel length. I've recently come to the likely conclusion that I may want to revisit my powder choices. For my 4" .44 Mag, N110 has yielded some good results, and I can use is with relative confidence as my Lyman's manual also provides data for a 4" barrel: nice to know figures I get are based on a similar firearm to theirs. Not so with my snub. I am not finding a sweet spot for my 2" barrel using my mid burn-rate powder. So I started thinking and that got me tied up in knots. My logic: If a slower powder is good because it keeps the pressure wave in the barrel building, it stands that this is most desirable in a longer barrel. Conversely, it then stands that a faster powder will give the most velocity from a shorter barrel, without wasting gases in a nuke-sized muzzle flare. But will it give more velocity or less or the same as a slower powder in that same barrel? Just because a slower burning powder charge has not all burnt up in the barrel, it doesn't mean that it won't already have built up respectable velocities. A faster powder's combustion will occur within the barrel length, but that does not mean it will generate more velocity in the time taken for the bullet to leave said barrel. And so now I find my logic starts chasing its own tail.... So what is the rule of thumb? __________________ When the right to effective self-defence is denied, that right to self-defence which remains is essentially symbolic. Freedom: Please enjoy responsibly.

June 28, 2013, 09:47 AM	#2
jim8115 Senior Member Join Date: July 23, 2011 Location: Arkansas Posts: 229	For what it is worth Been playing around with power pistol in 357 Magnum. I am finding that it really shines if you are loading for a short barrel. 158 cast 8.0 PP 1103 FPS from a 2 1/2" 686 , 1226 from a ruger 6"GP100 a loss of about 10% 158 Nosler JHP 8.0 PP 1030 from 2 1/2 , 1160 from 6" -11% For comparison 13.5 #9 1024 from the 2 1/2" , 1296 from the 6 " -23% Especially interesting, 8.0 PP actually outperforms the #9 load in the 2 1/2"

June 28, 2013, 03:29 PM	#4
Pond, James Pond Senior Member Join Date: July 12, 2011 Location: Top of the Baltic stack Posts: 6,079	Does this mean that, as a rule, the shorter the barrel, the faster the powder needed? __________________ When the right to effective self-defence is denied, that right to self-defence which remains is essentially symbolic. Freedom: Please enjoy responsibly.

June 28, 2013, 01:03 PM	#3
Don'tkillbill Senior Member Join Date: June 17, 2013 Location: East Coast of Canada Posts: 121	I really like 296 in my 357 magnum loads up to 20 grains with the 125 grain bullets. The 158 grain is better as it engages the rifling with more surface area. I shoot out of a 1892 and a 586. I get a little more speed out of the 16 inch barrel. Bill

June 28, 2013, 08:58 PM	#5
jim8115 Senior Member Join Date: July 23, 2011 Location: Arkansas Posts: 229	"Does this mean that, as a rule, the shorter the barrel, the faster the powder needed? " Well, it means that you will likely get better results with a somewhat faster powder from a short barrel. Now, there are those that will flat out tell you" if its faster in a long barrel, it will be faster in a short barrel". They are simply wrong. There may be exceptions, I dont know, because I havent tested every powder. But I have done tesing with h-110, #9, etc, comparing them to unique and power pistol. As a general rule, with 158 grain bullets anyway, I have found best results with faster powders in 2- 21/2 inch barrels. I think some folks think the huge recol and blast always = more velocity. A chronograph will prove this wrong JIM

June 29, 2013, 08:29 PM	#6
wncchester Senior Member Join Date: December 1, 2002 Posts: 2,832	"Now, there are those that will flat out tell you" if its faster in a long barrel, it will be faster in a short barrel". They are simply wrong." I'll flat out tell you that's simply wrong. Pressure in a handgun typically peaks in about 2-3" of bullet travel (some 3-5" in rifles). Velocity is totally dependant on the total pressure:time curve driving the bullet, not the peak pressure. Of course the ideal charge in a longer barrel will always be "faster" because the bullet will continue to accellerate as long as it's under pressure but the curve itself is what determines the best volocity at the moment of exit for any barrel length. For 'normal' barrel lengths (i.e., longer than maybe 1/2"), using a faster than optimum powder simply peaks and falls off too rapidly for best velocity no matter the barrel's length. Thus, whatever charge provides the optimum pressure curve for a given bullet in a given fire arm is independant of the barrel length.