slower powder's in a longer barrel vs. faster powders in a shorter barrel

Mr. Friendly

Mr. Friendly

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how would the recoil present itself? approximately the same or do you think there would be felt differences? :wave:

cartridge...say .308 Win, 165g TTSX out of an 18" barrel vs. 20" barrel, vs. 24" barrel, vs 28" barrel.

two further details to add to the equation. rifle is the same weight with the different barrel lengths vs. rifles that get lighter as the barrel get's shorter.
 
In the recoil formula the weight of the powder charge has a very dominant influence on recoil, much more so than bullet weight and velocity.

An example (my 280AI) with a 24" bbl and with the load I have the muzzle pressure is 11,526 psi, now if the barrel was 20" long 'same load' the muzzle pressure will be 14,429 psi.

With the 20" bbl the rocket effect of the exiting gases will be much more pronounced as will the sound.

Recoil will be very much the same but the firing event may be more harsh than with the longer barrel.
 
Recoil is a result of the physics of propelling everything that goes out the end of the barrel. That includes the bullet, and all the gasses and un-burned powder as well. So, more powder will increase recoil, and more powder will usually increase the velocity of the bullet, but just more powder mass alone will increase recoil.

The powder that produces the highest velocity in a long barrel will almost always produce the highest velocity in a short one too. Don't pick powder based on length of the barrel.
 
Larger charges of slower burning powder at higher velocities are going to kick more. The longer barrel is just going to add to it.

The good part is its just a .308 so the difference is between FA and four fifths of FA.
 
I have a Savage Hog Hunter in .308 with a 20 inch barrel, and I can tell the difference in recoil using IMR-3031 vs Varget with 168 grain bullets.

Note, I ruptured a disk in my neck in 1992 and had a cervical fusion. And my neck will tell me if it doesn't like the recoil if I do a lot of shooting. And the IMR-3031 loads below did not bother my neck like the Varget loads did when shooting 50 rounds.

Also Quickload will give you the percent of powder burned in a given length barrel with a given burn rate powder. Meaning the unburnt powder will add extra "rocket thrust" and blast. But the slower recommended powders will still give the highest velocities in shorter barrels.

Example in my S&W 29-5 .44 magnum with light loads of 231 will be 100% burnt in less than 3 inches of barrel length. "BUT" max loads of 296 will not be 100% burned in a 20 inch barrel. Meaning my light .44 magnum loads will not scorch and set the target on fire at 7 yards like 296 will. ;)

Below .308 loads from Dan Newberry OCW or Optimal Charge Weight Load Development method. Meaning the loads below are at the best accuracy nodes.

All Winchester brass. Reduce by .4 grains if using Lake City, or Federal brass. Reduce by .3 grains if using Lapua brass.

155 grain Sierra Matchking (or any comparable 155 grain match bullet)
45.6 grains of IMR 4895
or
46.5 grains of Varget, IMR 4064, or W748
there is a high node with Varget at about 47.8 grains (Nosler's max is 48 grains).

168 grain Sierra Matchking (or any comparable 168 grain match bullet)
43.6 grains of IMR 4895 (my all time favorite accuracy load)
or
44.5 grains of Varget or IMR 4064 or W748
there is a high node with Varget at or near 46 grains, Hodgdon's max...
or
39.0 grains of IMR 3031 (slower, but very accurate to 300 yards, a great close range tactical load).

175 Sierra Matchking
43.5 Varget, or 45.0 Varget (high node, be careful).
or
42.4 grains IMR 4895
or
43.4 grains of IMR 4064 (high node)
42.2 grains of IMR 4064 (low node)
or
43.5 grains of RL15

With 178 AMAX (Hornady)
42.0 grains IMR 4895
or
43.1 grains of Varget


Short barrel 16.5 inch 308 Winchester load development
https://rifleshooter.com/2017/01/short-barrel-16-5-inch-winchester-load-development/
 
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rral22 said:
Recoil is a result of the physics of propelling everything that goes out the end of the barrel. That includes the bullet, and all the gasses and un-burned powder as well. So, more powder will increase recoil, and more powder will usually increase the velocity of the bullet, but just more powder mass alone will increase recoil.

The powder that produces the highest velocity in a long barrel will almost always produce the highest velocity in a short one too. Don't pick powder based on length of the barrel.
Click to expand...

are you sure about that?
here's 308win simulation in quickload (anyone can check):

Cartridge : .308 Win. (SAAMI)
Bullet : .308, 168, Hornady BTHP 30501
Useable Case Capacity: 48.247 grain H2O = 3.133 cm³
Cartridge O.A.L. L6: 2.800 inch = 71.12 mm

Powder : Hodgdon TiteGroup 18.0gr, 55502psi
2.8" bbl 911fps
28" bbl 1984fps

Powder : Hodgdon Varget 44.07gr, 55504psi
2.8" bbl 885fps
28" bbl 2758fps


I chose 2.8" bbl as the shortest because there's where both powders pressures have peaked
the peak pressure is close ±2psi
Under this barrel length the fast Titegroup wins the speed contest by little but it does.
 
Quickload is a simulation and you're using an extreme case. I would not place much faith in either of the numbers - especially a 3% difference in claimed velocities.
 
Pr589 said:
Quickload is a simulation and you're using an extreme case. I would not place much faith in either of the numbers - especially a 3% difference in claimed velocities.
Click to expand...

that's true, it is an extreme case.
conceptually though, in a barrel as long as the length where the slow powder peaks, a faster powder produces more velocity because it peaks earlier.
there are few cartridges able to hold enough of a slow enough powder to show a practical difference and even fewer firearms with the exact barrel length.
 
Pr589 said:
Quickload is a simulation and you're using an extreme case. I would not place much faith in either of the numbers - especially a 3% difference in claimed velocities.
Click to expand...

With Quickload you need a chronograph and adjust the burn rate in Quickload until the two velocities match.

And then you will have your ball park chamber pressure and Quickload is tuned as close as it will ever be and better than a WAG.
 
legi0n said:
are you sure about that?
here's 308win simulation in quickload (anyone can check):

Cartridge : .308 Win. (SAAMI)
Bullet : .308, 168, Hornady BTHP 30501
Useable Case Capacity: 48.247 grain H2O = 3.133 cm³
Cartridge O.A.L. L6: 2.800 inch = 71.12 mm

Powder : Hodgdon TiteGroup 18.0gr, 55502psi
2.8" bbl 911fps
28" bbl 1984fps

Powder : Hodgdon Varget 44.07gr, 55504psi
2.8" bbl 885fps
28" bbl 2758fps


I chose 2.8" bbl as the shortest because there's where both powders pressures have peaked
the peak pressure is close ±2psi
Under this barrel length the fast Titegroup wins the speed contest by little but it does.
Click to expand...

Well, if you think comparing a 2.8 inch barrel to a 28 inch barrel is a good "argument" then, I stand corrected. I was stupid enough to think we would probably be talking about a reasonable difference in barrel lengths. Just stupid I guess. Sorry for the stupidity.
 
rral22 said:
Well, if you think comparing a 2.8 inch barrel to a 28 inch barrel is a good "argument" then, I stand corrected. I was stupid enough to think we would probably be talking about a reasonable difference in barrel lengths. Just stupid I guess. Sorry for the stupidity.
Click to expand...

it's not that, just that I hear quite often that "the powder that produces the highest velocity in a long barrel also produces the highest velocity in a short barrel".
which is almost but not quite entirely true :)

and yes, the comparison is not great, yet I could have used 2.8" vs 10" and the conclusion would have been the same.
 
here it is 2.8" vs 6":

Powder : Hodgdon TiteGroup 18.0gr, 55502psi
2.8" bbl 911fps
6" bbl 1409

Powder : Hodgdon Varget 44.07gr, 55504psi
2.8" bbl 885fps
6" bbl 1701
 
legi0n said:
it's not that, just that I hear quite often that "the powder that produces the highest velocity in a long barrel also produces the highest velocity in a short barrel".
which is almost but not quite entirely true :)

and yes, the comparison is not great, yet I could have used 2.8" vs 10" and the conclusion would have been the same.
Click to expand...

And my original statement was
The powder that produces the highest velocity in a long barrel will almost always produce the highest velocity in a short one too.
Click to expand...

The fact that there are ridiculous circumstances that, according to software, make my "almost always" actually true, proves what, exactly? I will continue to give the same advice to rifle cartridge re-loaders; The powder that gives the best velocity in a long barrel will almost always give the best velocity in a short one. For anyone who is looking at powder choices in real world re-loading, it is still good advice. I must however admit that, according to software, if you get ridiculous about the comparisons, I'm wrong. There, is that good enough?

Sometimes the internet brings out the absurd.
 
rral22 said:
And my original statement was

The fact that there are ridiculous circumstances that, according to software, make my "almost always" actually true, proves what, exactly? I will continue to give the same advice to rifle cartridge re-loaders; The powder that gives the best velocity in a long barrel will almost always give the best velocity in a short one. For anyone who is looking at powder choices in real world re-loading, it is still good advice. I must however admit that, according to software, if you get ridiculous about the comparisons, I'm wrong. There, is that good enough?

Sometimes the internet brings out the absurd.
Click to expand...

you may have missed the 2.8" vs 6" comparison
 
I'm with rral22 on this one. The powder that gives the highest velocity in a long barrel, also does so in a shorter,
reasonable length barrel. [not some ridiculous 2.8" length] This has been chewed over ad nauseum. Dave.
 
This topic has been hashed and re-hashed and will continue to be.

https://www.canadiangunnutz.com/for...th-Busting-Powder-Burn-Rate-vs-Barrel-Length?

I guess that the maxim that "The powder that produces the highest MV in long barrels (at maximum safe peak pressure) will the same in short barrels as well", needs to have the caveat "in barrels at least 4" long". Since only Prohibited firearms have barrels that short, I didn't consider it necessarily...
 
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