Efficiency of Revolvers vs. Semi Autos

[KFP]

This is purely a curious question and I realize that there are a lot of variables with this one, but which is more efficient?

There are revolvers that are capable of firing semi auto rounds, but in which platform does the round produce the highest velocity?

The first major hangup that I see in attempting to compare the two, is the method of measuring barrel length, secondly, we have the issue of where each platform loses the most energy. Barrel length of a revolver does not take into account the cylinder, whereas the barrel length of a semi auto includes the chamber. A semi auto loses energy through the recoil of the slide, but seems to seal the expansion of the gas better than a revolver which loses the expansion of the gas through the gap in the cylinder and the barrel, but not through recoil (supposing the gun is stationary).

Is there any way to compare the two as equals? Thoughts?

[WildBill]

KFP - You are correct that the velocity from a revolver will be less because of the gap between the cylinder and barrel. This is a result of lost gas pressure that escapes from the gap. However, the velocity [or energy] of a bullet fired from a semi-automatic is not decreased by the recoil of the slide. So, I believe that identical rounds fired from identical barrels lengths will always have have greater velocity when fired from a semi-automatic. If anyone has some chrono data that disputes this theory, I would be happy to see it.

[USA1]

Is there any way to compare the two as equals? Thoughts?

maybe with ballistic gelatin ?

[KFP]

KFP - You are correct that the velocity from a revolver will be less because of the gap between the cylinder and barrel. This is a result of lost gas pressure that escapes from the gap. However, the velocity [or energy] of a bullet fired from a semi-automatic is not decreased by the recoil of the slide. So, I believe that identical rounds fired from identical barrels lengths will always have have greater velocity when fired from a semi-automatic. If anyone has some chrono data that disputes this theory, I would be happy to see it.

Mr. Camp perhaps?

[WildBill]

KFP - You are correct that the velocity from a revolver will be less because of the gap between the cylinder and barrel. This is a result of lost gas pressure that escapes from the gap. However, the velocity [or energy] of a bullet fired from a semi-automatic is not decreased by the recoil of the slide. So, I believe that identical rounds fired from identical barrels lengths will always have have greater velocity when fired from a semi-automatic. If anyone has some chrono data that disputes this theory, I would be happy to see it.

Mr. Camp perhaps?

As I recall, he recently, he reviewed a 9mm revolver.

[Stephen A. Camp]

Hello. No, I've not reviewed any 9mm revolvers; sorry.

Assuming that a person is speaking of the same effective barrel lengths, I think that the automatic theoretically should produce the highest velocity due to the revolver's cylinder gap but barrel lenght differs on autoloaders vs. revolvers. The revolver's bbl length is just that, the length of rifled tube that the bullet passes through. On the autoloader, the chamber is included in the listed bbl length, but subtracting the case length for the particular cartridge gives a truer measurement of the barrel length through which the bullet can accelerate. For lack of a better term, I call this "effective barrel length".

In the end, with the usual variations, shot-to-shot in the ammunition and the slightly different barrel dimensions, it is not unusual to now and again find a shorter barreled gun producing higher velocity than one with a longer barrel.

Surprisingly, cylinder gaps do not seem to lower velocity very much; I've often wondered if the little extra length of the cylinder in front of the bullet counteracts that? I cannot speak to the 9mm but I can make some comparisons with .45 ACP on the revolver vs autoloader barrel length and velocity thing. In most instances, to me it seems that velocities for two guns with the same or approximately equivalent bbl lengths are more dependent upon the individual example than a rule. It gets more confusing when comparisons show that Brand A with an 3" bbl gets uniformly higher bullet speeds than Brand B with the same length bbl EXCEPT that it doesn't happen for ALL loads. With some loads, Brand B might very well beat Brand A. You just have to chronograph the load from the gun in question. The figures below are for average velocities based on 10 shots fired 10' from the chronograph screens.

S&W Model 625 w/3" bbl:

Winchester USA 230-gr. FMJ: 797 ft/sec

Winchester Ranger 230-gr. JHP: 843

SIG-Sauer P220 w/4.4" bbl: (Effective bbl length is 4.4-.889 = 3.51", a slight advantage to the auto)

Winchester USA 230-gr. FMJ: 771

Winchester Ranger 230-gr. JHP: 857

If you want to just go strickly with listed bbl length, here are what I got with a friend's 3" Cold Defender:

Winchester USA 230-gr. FMJ: 765

Winchester Ranger 230-gr. JHP: 797

Best.

[WildBill]

I would say "Define efficiency" first.

From KFP's question, I assumed efficiency meant converting a certain quanity of smokeless powder into the kinetic energy of a bullet. Smokeless powders have different burnrates and may be more effecient for a given barrel length so you would have to test the exact same load in each type of handgun.

[KFP]

I would say "Define efficiency" first.

From KFP's question, I assumed efficiency meant converting a certain quanity of smokeless powder into the kinetic energy of a bullet. Smokeless powders have different burnrates and may be more effecient for a given barrel length so you would have to test the exact same load in each type of handgun.

Exactly the way that I was thinking.

Mr. Camp - It's interesting to look at the velocities you obtained, from those it appears that the revolver actually has a slight edge - but as you said, making a hard and fast rule seems difficult.

[MoJo]

The variables involved in this are astounding. Two guns made one after the other can and often do exhibit wide variances in velocity. Each gun is a law unto itself. I have a pair of M&P 4.25" 40 S&W pistols. I'll try to get out to the range this week with the chronograph and clock some loads out of both of them. It should prove interesting.

[CompVest]

Our M&P9's (standard) chrono the same.

[Stephen A. Camp]

Hello. Consistency may be better with the computer-assisted machining being done these days; I'm no expert on much except finding the supper table on time so I cannot honestly say.

I can provide some figures from three different .45 1911-pattern pistols having 5" bbls:

Springfield Armory LW Gov't Model w/5" bbl:

Winchester USA 230-gr. FMJ: 801 ft/sec

Winchester Ranger 230-gr. JHP: 870 ft/sec

Norinco 1911 w/5" bbl:

Winchester USA 230-gr. FMJ: 774

Winchester Ranger 230-gr. JHP: 843

Kimber Classic 5":

Winchester USA 230-gr. FMJ: 840

Winchester Ranger 230-gr. JHP: 881

Best.

[casingpoint]

The author below is cites a revolver flash gap velocity loss of 100-200 fps. Significant by any standard.

Remington would have exact figures since their revolver test barrels are ported to equal flash gap loss.


Gunshot wounds: practical aspects of firearms, ballistics, and forensic ...
By Vincent J. M. Di Maio
http://books.google.com/books?id=VbrDbb ... q=&f=false" onclick="window.open(this.href);return false;

http://tinylink.com/?OoFjtBoUvy" onclick="window.open(this.href);return false;

[KFP]

It seems to me that both designs have weaknesses/advantages over the other in obtaining the highest velocity from the same rounds. I'm still struggling to understand how the recoil of the slide on a semi auto doesn't result in a loss of energy from the round. Any explanations?

For some reason this question has me intrigued, even though I'm not sure there is a definitive answer.

I appreciate the help thus far