revolver vs semi auto efficiency

[Fletchette]

In both the revolver and semi-auto some of the cartridge's energy is "wasted". For the revolver, some of the propellent gasses are lost due to the gap between cylinder and barrel. For the semi-auto, some energy is used for case ejection and feed of a new round.

In general, what are these losses? 10%? 25%? Which design is inherently more efficient?

I think a good way to test would be to fire an identical round in a single-shot pistol of identical barrel length and compare with muzzle velocity of the cartridge in a revolver or semi-auto. Is there any data like this available?

 

[RyanM]

Semi autos rounds lose a pretty minimal amount of energy from the action. That's exactly like saying that recoil leeches away energy, so the tighter you hold the gun, the faster the bullet goes. And if you "punch" the gun forward, you get even more velocity! And if you scream "gat gat GAT!" with each shot, the sound waves from your voice bounce off the back of the bullet and give even more velocity!

Semi-autos use the recoil impulse to power the action. If there is no action, you still have the same amount of recoil impulse. The only velocity "lost" will be due to the (comparatively very slow) backwards movement of the barrel.

Cylinder gap on the other hand is a real source of velocity loss.

 

[Car Knocker]

I think a good way to test would be to fire an identical round in a single-shot pistol of identical barrel length and compare with muzzle velocity of the cartridge in a revolver or semi-auto. Is there any data like this available?

Rounds fired from handguns of the same model and with the same barrel length will develop different velocities due to minute barrel variations, chamber variations, etc. When you introduce even more variables into the equation, the results will be unreliable.

 

[WT]

Fletch - yes, that information is available.

A few years ago SWAT magazine did just such a comparison using a 9mm Ruger revolver and a 9mm Ruger pistol. They used various factory ammunition loadings. Coincidently, the distance from the breech to the muzzle was the same on the two Ruger products.

One surprising result was that, using some cartridges, the muzzle velocity for a revolver was higher than the auto - even taking the BC gap into consideration. In other cases the autos exhibited higher MV.

 

[1911Tuner]

Velocity Loss

Much adieu over...not much.

A difference of 30 fps in velocity between two identical bullets is of no practical signifigance. Factory-loaded ammo will often vary that much from shot to shot within the same lot. You'll never know the difference and neither will the target.

 

[ribbonstone]

That cylinder gap doesn't waste all that much energy, at least not one in industry specs....but it does bleed off a bit. How much isn't easy to measue, but from tests run setting the gap at differnt settings (and the one I remember reading didn't use a Dan Wesson...although that would work) it's pretty minor...call it no more than 3%.

Bottom line: The differnce from .000 to .003" is less than the natural variation between different barrels.

Have been some semi-autos (mostly in the lower powdered rounds) that allowed the slide to be locked in place to prevent semi-auto cycling. Have had two old Savage .22rifles that allowed locking the bolt...and just like the pistols, if there is any difference it's less than the normal vel. variation of the ammo.
------
I too had a 2 3/4" Ruger Speed Six in 9mm and a Browning HP out on the same day. Back then, light weight bullets at high velcoity seemed worth exploration and was 'graphing some BlueDot/90gr.JHP loads. The difference between the Ruger and Browning semi-auto was less than 10fps (they both hung in there at 1400-1410fps averages).

Did notice one odd effect.

Shooting side-by-side into water jugs, the revolver's bullets tended to fragment more than the Semi-auto's loads. Same loads, same bullets, same velocity...but the revolver's rifling was deeper, and the bullet had a long distance to go to find engravement. Best guess is that that little bullet, moving along at a very fast clip, smacking into the deep rifling, stressed that jacket more than the semi-auto did...which allowed what should have been identical loads to sjow that fragmentation when shot from the revovler.

-----
BTW: Bullets can be moving pretty fast by the end of the cylinder. Guess it was illegal (would be a smooth bore pistol) but enough years have passed..fired a Dan Wesson without any barrel attached over a chronograph....some of the 158gr. loadings were doing a bit better than 800fps with a barrel length of "zero" (most were in the 640-700fps range, but a few brands were evidently loaded hot-and fast). That's a pretty impressive velocity...consider standing back 10 or 15 feet and shooting at a vice mounted barrel with a .38special and the stress applied if you were to shoot one dead center of that mounted barrel.

 

[rockstar.esq]

depends of if your running "unleaded"!

 

[MachIVshooter]

In my experience, revolvers and auto's with the same barrel length tend to achieve very similar velocities. However, a 4" auto is 4" from the rear of the chamber to the muzzle. A 4" revolver is about 5-1/2"+ from the rear of the cylinder to the muzzle. So it is reasonable to assume that a revolver needs a little bit longer tube to compensate for the cylinder gap pressure loss.

 

[Vitamin G]

And if you scream "gat gat GAT!" with each shot, the sound waves from your voice bounce off the back of the bullet and give even more velocity!

This only works for me when I'm shooting subsonic rounds.

 

[Fletchette]

Guess it was illegal (would be a smooth bore pistol) but enough years have passed..fired a Dan Wesson without any barrel attached over a chronograph....

A smooth bore pistol is illegal? That's news to me. Why on earth would such a thing be illegal (not that logic has ANYTHING to do with gun laws...)?

Anyhow, thanks for all the info.

 

[ribbonstone]

The logic is kind of twisted...but if it's smooth bore cartridge gun, under 18" of barrel, and under 26" in over all length, it's an illegal sawed off shotgun (reguardless of bore size). Are some semi-antique smooth bores that qualify under the C&r rules and only require a small fee, and the smooth-bore rules don't apply to muzzle loaders. So yes, smooth bore cartridge revovlers (or semi-autos...or single shots...etc) are not legal.

Removing the barrel from a revolver leaves you with a smoothbore pepperbox....and being smoothbore and taking cartridges, it's illegal.

 

[MachIVshooter]

The logic is kind of twisted...but if it's smooth bore cartridge gun, under 18" of barrel, and under 26" in over all length, it's an illegal sawed off shotgun (reguardless of bore size). Are some semi-antique smooth bores that qualify under the C&r rules and only require a small fee, and the smooth-bore rules don't apply to muzzle loaders. So yes, smooth bore cartridge revovlers (or semi-autos...or single shots...etc) are not legal

SBS is not defined by smooth vs. rifled bore. There is nothing illegal about a smooth bore pistol, they just aren't very accurate. The reason pistols cannot be chambered for shotgun shells (other than the .410) is bore size; Non-shotguns with a bore over .500" are considered destructive devices (a few exceptions exist for dangerous game rifles). The .410 bore is .45" and can be had in handguns, usually derringers that also fire the .45 Colt cartridge.

The law you refer to regarding 18" barrel and 26" OAL applies to the shotgun only. A handgun can be any firearm with a barrel under 16", no shoulder stock and a bore size .500" or under. If one were to attach a shoulder stock to a .45 C/ .410 derringer, then it would be considered either an SBR or SBS, depending on which round was in it when you got caught. But so long as the firearm remains in a handgun configuration, it is perfectly legal.

If the law has changed and for some reason the rest of us aren't aware, please cite the section in the BATF books with a link.

 

[Fletchette]

Removing the barrel from a revolver leaves you with a smoothbore pepperbox....

Doesn't the Dan Wesson have a screw in barrel? If so, then with the barrel removed it isn't a smooth bore, it is a very short barreled revolver with very aggressive rifling!

 

[Davo]

Wait a minute...

Ryan are you saying Ive been yelling GAT! for no reason?