Hello!
This is my first post (and topic) in here, but I have lurked this board for a few years and thanks to you all, my knowledge about firearms, physics etc. has greatly expanded. Thank you for all of this.
However, there are a few questions that, I think, have never been asked or answered, or at least I can't find the answers myself.
1. .357 Magnum and long barrels.
Why is .357 Mag benefitting so much from really long barrels (up to around 12-14")? When compared to .357 Sig it seems clear that Magnum at equal velocity and bullet weight always benefits way more from longer barrels.
According to http://www.ballisticsbytheinch.com/357sig.html
http://www.ballisticsbytheinch.com/357mag.html
Cor-Bon 125gr JHP, 357 Sig: 4" barrel: 1468 fps, best velocity out of 14" barrel: 1747 fps. Difference: 279 fps. Increase in %: 19%
Cor-Bon 125gr JHP, 357 Magnum: 4" barrel: 1496 fps (so far it looks like an equally powerfull/slightly hotter load), best velocity out of 16" barrel: 2119 fps. Difference: 623 fps. Increase in %: 41,6%.
And if you take a look at any other .357 Sig or 9mm +P load, the same is always true - they benefit much much less from longer barrels than .357 Magnum does.
Now, 125gr is pretty much the most popular self defence bullet in .357 Magnum and I doubt anyone @Cor-Bon would be loading this kind of ammunition with lever-action rifles in mind, yet it seems it absolutely shines when fired from the rifle's barrel.
So what causes this HUGE difference in performance? Is it because .357 Magnum ammo manufacturers use v. slow burning powders? Why would they (theoretically it's just more flash, more report, for no real benefit out of most popular 2,5-4" barrels - or am I wrong)? Or does it have something to do with case length?
2. Revolvers - muzzle velocity - cylinder gap.
I have carefully read the whole section of BBI about cylinder gap and apparently its impact on muzzle velocity is rather small.
Now take a look at BBI testing and you'll notice that their 4" S&W 686, which is an excellent performer in muzzle velocity department, compared to their other wheelguns actually was doing a bit worse than their 4" test barrel setup, measured from the breech face.
This puzzles me, since 686 with 4" barrel has the advantage of a whole cylinder that effectively allows the bullet to be accelerated for a longer time.
I expected the revolver to achieve velocities slightly below those of 5 inch barrel test setup. Yet it seems that 4" test barrel already outperformed it.
Same isn't true for semi-auto pistols. The "real world" guns basically achieve v. similiar velocities to the test barrel. It's logical - similiar barrel length, similiar velocity.
So, what causes such a big loss of muzzle velocity in revolvers? Cylinder gap tests indicate that revolver vs revolver, 1 with 0,006 gap and another with no gap the difference is not so great, and I'm pretty sure their test 686 is WAY more tight than 0,006:
For Federal Premium, .357 magnum, 158 gr. Hydra-Shok JHP:
4" revolver barrel, 0,006 gap: 1211 fps
4" revolver barrel, no gap: 1282 fps
and we're talking about 2 revolvers here, so in both cases bullet has exactly the same conditions (no cylinder-length advantage.
Also it's very interesting that in this test all of the sudden .357 Magnum no loner performs so great out of long barrel:
Federal Premium, .357 magnum, 158 gr. Hydra-Shok JHP:
1)16" revolver, no gap: 1492fps
2) 4" revolver, no gap: 1282 fps
(as a comparison, test barrel setup: 4": 1332 fps - 50 fps faster than 4" revolver with no gap!, 16": 1741 fps - 250 fps more)
Cor-Bon, .357 magnum, 125 gr. DPX:
1) 1246 fps
2) 1526 fps
(test barrel 4": 1471 fps - 225 fps more!, 16": 1946 fps - 420 fps more, WOW!).
So:
What makes a revolver such an inferior performer compared to "test barrel setup" in almost all cases? Why isn't the additional space for the bullet to accelerate positively affecting the muzzle velocity?
What may have caused muzzle velocity of the revolver-with-no-gap to be that much lower than muzzle velocity out of test barrel?
Is it simply all because of flawed testing criteria/conditions? Or is the presence of the cylinder actually negatively influencing the muzzle velocity. If so - why? Or maybe the revolver testing setup was somehow "broken" and their cylinder gap test results actually lead to underestimation of gap impact on the muzzle velocity?
Thank you in advance for your responses. Sorry for all the mistakes I've made - unfortunately my English is still rather poor, but I'm working on it even right now.
Now this is just mind-boggling:
http://smith-wessonforum.com/s-w-re...sults-38spl-9mm-38-super-9x23-winchester.html
Taurus 905 has only 2 inch barrel and it pretty much matches Beretta 8000. Which may indicate that the problem with revolver muzzle velocity being so low is actually caused by something in cylinder. 9mm headspaces on the case mouth. Is it possible that differently cut cylinder causes all the difference, allowing the revolver to all of the sudden match the "normal pistol" setups?
This is my first post (and topic) in here, but I have lurked this board for a few years and thanks to you all, my knowledge about firearms, physics etc. has greatly expanded. Thank you for all of this.
However, there are a few questions that, I think, have never been asked or answered, or at least I can't find the answers myself.
1. .357 Magnum and long barrels.
Why is .357 Mag benefitting so much from really long barrels (up to around 12-14")? When compared to .357 Sig it seems clear that Magnum at equal velocity and bullet weight always benefits way more from longer barrels.
According to http://www.ballisticsbytheinch.com/357sig.html
http://www.ballisticsbytheinch.com/357mag.html
Cor-Bon 125gr JHP, 357 Sig: 4" barrel: 1468 fps, best velocity out of 14" barrel: 1747 fps. Difference: 279 fps. Increase in %: 19%
Cor-Bon 125gr JHP, 357 Magnum: 4" barrel: 1496 fps (so far it looks like an equally powerfull/slightly hotter load), best velocity out of 16" barrel: 2119 fps. Difference: 623 fps. Increase in %: 41,6%.
And if you take a look at any other .357 Sig or 9mm +P load, the same is always true - they benefit much much less from longer barrels than .357 Magnum does.
Now, 125gr is pretty much the most popular self defence bullet in .357 Magnum and I doubt anyone @Cor-Bon would be loading this kind of ammunition with lever-action rifles in mind, yet it seems it absolutely shines when fired from the rifle's barrel.
So what causes this HUGE difference in performance? Is it because .357 Magnum ammo manufacturers use v. slow burning powders? Why would they (theoretically it's just more flash, more report, for no real benefit out of most popular 2,5-4" barrels - or am I wrong)? Or does it have something to do with case length?
2. Revolvers - muzzle velocity - cylinder gap.
I have carefully read the whole section of BBI about cylinder gap and apparently its impact on muzzle velocity is rather small.
Now take a look at BBI testing and you'll notice that their 4" S&W 686, which is an excellent performer in muzzle velocity department, compared to their other wheelguns actually was doing a bit worse than their 4" test barrel setup, measured from the breech face.
This puzzles me, since 686 with 4" barrel has the advantage of a whole cylinder that effectively allows the bullet to be accelerated for a longer time.
I expected the revolver to achieve velocities slightly below those of 5 inch barrel test setup. Yet it seems that 4" test barrel already outperformed it.
Same isn't true for semi-auto pistols. The "real world" guns basically achieve v. similiar velocities to the test barrel. It's logical - similiar barrel length, similiar velocity.
So, what causes such a big loss of muzzle velocity in revolvers? Cylinder gap tests indicate that revolver vs revolver, 1 with 0,006 gap and another with no gap the difference is not so great, and I'm pretty sure their test 686 is WAY more tight than 0,006:
For Federal Premium, .357 magnum, 158 gr. Hydra-Shok JHP:
4" revolver barrel, 0,006 gap: 1211 fps
4" revolver barrel, no gap: 1282 fps
and we're talking about 2 revolvers here, so in both cases bullet has exactly the same conditions (no cylinder-length advantage.
Also it's very interesting that in this test all of the sudden .357 Magnum no loner performs so great out of long barrel:
Federal Premium, .357 magnum, 158 gr. Hydra-Shok JHP:
1)16" revolver, no gap: 1492fps
2) 4" revolver, no gap: 1282 fps
(as a comparison, test barrel setup: 4": 1332 fps - 50 fps faster than 4" revolver with no gap!, 16": 1741 fps - 250 fps more)
Cor-Bon, .357 magnum, 125 gr. DPX:
1) 1246 fps
2) 1526 fps
(test barrel 4": 1471 fps - 225 fps more!, 16": 1946 fps - 420 fps more, WOW!).
So:
What makes a revolver such an inferior performer compared to "test barrel setup" in almost all cases? Why isn't the additional space for the bullet to accelerate positively affecting the muzzle velocity?
What may have caused muzzle velocity of the revolver-with-no-gap to be that much lower than muzzle velocity out of test barrel?
Is it simply all because of flawed testing criteria/conditions? Or is the presence of the cylinder actually negatively influencing the muzzle velocity. If so - why? Or maybe the revolver testing setup was somehow "broken" and their cylinder gap test results actually lead to underestimation of gap impact on the muzzle velocity?
Thank you in advance for your responses. Sorry for all the mistakes I've made - unfortunately my English is still rather poor, but I'm working on it even right now.
Now this is just mind-boggling:
http://smith-wessonforum.com/s-w-re...sults-38spl-9mm-38-super-9x23-winchester.html
Taurus 905 has only 2 inch barrel and it pretty much matches Beretta 8000. Which may indicate that the problem with revolver muzzle velocity being so low is actually caused by something in cylinder. 9mm headspaces on the case mouth. Is it possible that differently cut cylinder causes all the difference, allowing the revolver to all of the sudden match the "normal pistol" setups?
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