does a bullet loose velocity through a pistol over a revolver?
- Thread starter GUNSNGOLD
- Start date
Pressure is everything. If even the slightest bit of pressure gets bled off, you will lose acceleration, and acceleration is what counts. You start at 0, and gain speed all the way down a barrel, as the gasses expand, powder keeps burning, and the bullet approaches maximum speed. Wherever the leak is, from tiny and insignificant to large, it will effect acceleration and eventual muzzle velocity. If you welded that gap shut, you would find that maybe you have at most a 1% or so boost in velocity. That figure is absolute guesswork
In a lot of cases, I really believe that this effect is going to be truly insignificant. At pistol velocities 30 -50 fps won't make a significant difference, and I doubt that the difference would even be that high.
As was said before, each firearm will be different, and two identical revolvers may have big differences between them with identical ammunition.
I understand wanting to know the answer, you're learning. My thoughts, though, are that this is a total non issue. Choose the handgun and round you want, and don't worry about abstract things like cylinder gap effects.
In a lot of cases, I really believe that this effect is going to be truly insignificant. At pistol velocities 30 -50 fps won't make a significant difference, and I doubt that the difference would even be that high.
As was said before, each firearm will be different, and two identical revolvers may have big differences between them with identical ammunition.
I understand wanting to know the answer, you're learning. My thoughts, though, are that this is a total non issue. Choose the handgun and round you want, and don't worry about abstract things like cylinder gap effects.
I chronographed bullets shot from my S&W model 41 semiauto and my S&W model 17 revolver a while back. I don't remember the exact velocities but the semi auto was faster by about 50 fps or so.
The slide on the unlocked blowback system on my 41 has a mass of 199 grams or 3070 grains which is 77 times the mass of the bullet. That means that when the bullet travels one inch, the slide moves backwards 1/77 of an inch. When the bullet reaches the end of the 7 inch barrel, the slide has traveled back 7/77 or .09 inches. Since a .22lr case is .606 inches long, the breech is still sealed.
If the bullet comes out at 1000 fps, then the slide is moving backwards at 1000/77 fps or 13 fps. Thirteen fps would give the 3070 grain slide 1.15 ft-lb of kinetic energy. 1000 fps gives the 40 grain bullet 88.7 ft-lb of energy. If we had a breech block of infinite mass so there would be no movement at all, we may assume that the 1.15 ft-lb of energy given to the slide would have been given to the bullet giving it 88.7 + 1.15 = 89.85 ft-lb of energy. 89.85 ft-lb of energy comes out to 1006.8 fps. That's a difference so small that it would be lost in the shot to shot velocity variation of normal ammo.
The slide on the unlocked blowback system on my 41 has a mass of 199 grams or 3070 grains which is 77 times the mass of the bullet. That means that when the bullet travels one inch, the slide moves backwards 1/77 of an inch. When the bullet reaches the end of the 7 inch barrel, the slide has traveled back 7/77 or .09 inches. Since a .22lr case is .606 inches long, the breech is still sealed.
If the bullet comes out at 1000 fps, then the slide is moving backwards at 1000/77 fps or 13 fps. Thirteen fps would give the 3070 grain slide 1.15 ft-lb of kinetic energy. 1000 fps gives the 40 grain bullet 88.7 ft-lb of energy. If we had a breech block of infinite mass so there would be no movement at all, we may assume that the 1.15 ft-lb of energy given to the slide would have been given to the bullet giving it 88.7 + 1.15 = 89.85 ft-lb of energy. 89.85 ft-lb of energy comes out to 1006.8 fps. That's a difference so small that it would be lost in the shot to shot velocity variation of normal ammo.
Here is what I suspect.
If you took 50 revolvers (same model) with varying gaps. Say from .002 to .010, and then took same ammo and chronographed six shots from each pistol. Then took the standard deviation from total of all the results.
I bet you could not tell which revolver had the large gap by looking at the standard deviations. In other words, the velocity variation would be too small to detect by looking at the chronograph numbers.
If you took 50 revolvers (same model) with varying gaps. Say from .002 to .010, and then took same ammo and chronographed six shots from each pistol. Then took the standard deviation from total of all the results.
I bet you could not tell which revolver had the large gap by looking at the standard deviations. In other words, the velocity variation would be too small to detect by looking at the chronograph numbers.
The question poses interesting theory, but I'm not sure it amounts to much in the real world:
1) In either a pistol or a revolver, propellant combustion is complete before the bullet begins to move from the case.
2) After that, the force that causes the bullet to accelerate is the pressure from the confined combustion product gasses.
3) All other things being equal -- a condition that is impossible in context to obtain -- the revolver should show a bit less muzzle velocity, simply because some quantity (however small) of the pressurized gas has been vented to the atmosphere before the bullet clears the muzzle.
4) As others have noted, the energy required to cycle a recoil-operated pistol is not tapped from the force applied to accelerate the bullet during in-bore passage.
5) In real life, the muzzle velocity will vary between examples of the same make, model and caliber of pistol or revolver, shooting the same ammunition. Indeed, the muzzle velocity will vary from round to round when shooting a single pistol or revolver. These variations are larger, far larger, than the theoretical velocity penalty of the revolver cylinder-to-cone gap. As a result, that penalty is statistically invisible.
1) In either a pistol or a revolver, propellant combustion is complete before the bullet begins to move from the case.
2) After that, the force that causes the bullet to accelerate is the pressure from the confined combustion product gasses.
3) All other things being equal -- a condition that is impossible in context to obtain -- the revolver should show a bit less muzzle velocity, simply because some quantity (however small) of the pressurized gas has been vented to the atmosphere before the bullet clears the muzzle.
4) As others have noted, the energy required to cycle a recoil-operated pistol is not tapped from the force applied to accelerate the bullet during in-bore passage.
5) In real life, the muzzle velocity will vary between examples of the same make, model and caliber of pistol or revolver, shooting the same ammunition. Indeed, the muzzle velocity will vary from round to round when shooting a single pistol or revolver. These variations are larger, far larger, than the theoretical velocity penalty of the revolver cylinder-to-cone gap. As a result, that penalty is statistically invisible.
There's an interesting table...
...published in the Speer reloading manuals. They tested .357 magnum loads in a variety of revolvers. Even with revolvers from the same manufacturers, the velocity differences were surprising.
If you wanted to compare "somewhat like-to-like", try a Smith 25/625 with a five inch barrel, to full-size 1911. Equal barrel lengths. Or, try the same with a 4" revolver compared to a Commander-sized semi-auto.
The bench mark is really attained using a pressure barrel of defined length. That would be more of an absolute standard, than either a revolver or pistol.
...published in the Speer reloading manuals. They tested .357 magnum loads in a variety of revolvers. Even with revolvers from the same manufacturers, the velocity differences were surprising.
If you wanted to compare "somewhat like-to-like", try a Smith 25/625 with a five inch barrel, to full-size 1911. Equal barrel lengths. Or, try the same with a 4" revolver compared to a Commander-sized semi-auto.
The bench mark is really attained using a pressure barrel of defined length. That would be more of an absolute standard, than either a revolver or pistol.
pendennis nailed it, the auto performs better than a pistol of similar barrel length, in some cases much better. The auto maintains a locked breach until after the bullet has left the barrel so all of the energy is available to push the bullet until it is gone. The remaining energy then cycles the action and loads a new round into the chamber. A true work of art in IMO. A revolver appears to be a more efficient design but that actually isn't true. There is always a gap between the cylinder and the barrel where pressure is released. This pressure release occurs just after the bullet leaves the cartridge and continues to purge as the bullet travels down the barrel. It's the reason the .22magnum doesn't perform better in revolvers. The cartridge is so long that the bullet has just left it and already pressure is being bled off.
Even in guns of the same type (revolvers) with the same barrel length by different manufacturers, you'll get some significant variation.
Load 1
S&W = 887 fps
Ruger = 910 fps
Not too bad at all.
Load 2
S&W = 792 fps
Ruger = 914 fps
Really? 122 fps? Yep. I ran three 5 shot strings.
Load 3
S&W = 794 fps
Taurus = 823 fps
Again, not bad.
With one .38 Special +P load:
What the VihtaVuori manual said I should get = 1046 fps
What I actually got = 829 fps with very low pressure.
Over 200 fps less than the manual predicted and a long, long way from +P pressure.
This why you need to have a chronograph!!
Load 1
S&W = 887 fps
Ruger = 910 fps
Not too bad at all.
Load 2
S&W = 792 fps
Ruger = 914 fps
Really? 122 fps? Yep. I ran three 5 shot strings.
Load 3
S&W = 794 fps
Taurus = 823 fps
Again, not bad.
With one .38 Special +P load:
What the VihtaVuori manual said I should get = 1046 fps
What I actually got = 829 fps with very low pressure.
Over 200 fps less than the manual predicted and a long, long way from +P pressure.
This why you need to have a chronograph!!
My 5 inch Coonan Shoots 357 magnums faster than my 5 inch S&W with my reloads and the few factory ammo I have tried (Winchester, Buffalo Bore)
Id say the Semi is a bit faster at least in 357 magnum. In the area of about 80-200FPS (big difference in different loads) . Lighter bullets seem to gain more speed than the heavier ones
Id say the Semi is a bit faster at least in 357 magnum. In the area of about 80-200FPS (big difference in different loads) . Lighter bullets seem to gain more speed than the heavier ones
Therealkoop
New member
Autos = bbl measured from end of chamber
revolvers = bbl measured from forward of the gap.
a 4" revolver has a lot more bbl than a 4" auto.
revolvers = bbl measured from forward of the gap.
a 4" revolver has a lot more bbl than a 4" auto.
Therealkoop said:
Don't agree. 4" is 4".
Measurement from the end of the chamber gives the same amount of barrel as measurement from the end of gap.....actually the barrel on a revolver is from the forcing cone.
Ok, I have to correct myself.
http://www.nonameoutdoors.com/?q=node/734
Therealkoopu you are correct.....that's twice this week I have made a mistake. Only two mistakes for the year, not bad.
Last edited:
Actually this is not true 100% of the time. Years of shooting large bore handguns with slow powders has taught me that with certain loads (in fact, with most pistol loads) not ALL of the powder is burned before the bullet begins to move. Sometimes its not even all burned when the bullet leaves the barrel!
I did not say that "all powder" was burned about the time the slug begins to move, but that "combustion was complete" by that time. Any unburned powder resulting from a too-low-pressure load using a too-slow powder is unburned because it never ignited, not because it ran out of time.
The advent of practical piezo devices permits time series records of chamber pressure during the firing of smokeless powder cartridges. The end point of combustion occurs at the point of peak chamber pressure. The curves reveal that this occurs so early in the cycle that the bullet has only barely moved from the case, if at all.
The advent of practical piezo devices permits time series records of chamber pressure during the firing of smokeless powder cartridges. The end point of combustion occurs at the point of peak chamber pressure. The curves reveal that this occurs so early in the cycle that the bullet has only barely moved from the case, if at all.
Nitrocelluose is a underoxidized propellent, it does not have enough oxygen atoms in the molecule to convert all the carbon into CO2 and all the hydrogen atoms into H2O.
The muzzle flash is not the powder still burning, it's the carbon monoxide, hydrogen etc. reigniting and finishing the burn when it hits the oxygen in the atmosphere.
When you shoot a .22 long rifle out of a rifle at night, you will see a small muzzle flash, but we know the explosion is over because a 6 inch pistol shoots a .22 about 90% as fast as the rifle and when you get barrels longer than 16 inches or so, the velocities actually start to drop. The burn was over long before the bullet exited the barrel but the left over compounds, many of them probably highly reactive free radicals, reignite upon hitting the air.
The muzzle flash is not the powder still burning, it's the carbon monoxide, hydrogen etc. reigniting and finishing the burn when it hits the oxygen in the atmosphere.
When you shoot a .22 long rifle out of a rifle at night, you will see a small muzzle flash, but we know the explosion is over because a 6 inch pistol shoots a .22 about 90% as fast as the rifle and when you get barrels longer than 16 inches or so, the velocities actually start to drop. The burn was over long before the bullet exited the barrel but the left over compounds, many of them probably highly reactive free radicals, reignite upon hitting the air.