Revolver velocity vs. Semi-Auto


July 11, 2008, 08:35 PM
I have a question that I have not been able to search an answer for. I do not own a revolver, but am curious about the velocity from a revolver vs a semi-auto. Since a semi-auto must use some of the energy from a round to eject the case and a revolver does not...does a revolver provide higher velocity from an exact same round as a semi-auto would?


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General Geoff
July 11, 2008, 08:42 PM
Not generally, since what little energy is lost from cycling the action of a semiauto is also lost in the barrel-cylinder gap of a revolver.

Barrel length will make more of a difference.

July 11, 2008, 08:54 PM
Except for blow-back operated, or gas operated, weapons (by far the minority of semi-autos), the breech of a semi-auto is FULLY LOCKED until after the bullet exits the barrel. The "energy is wasted" operating the mechanism is negligible.



July 11, 2008, 08:56 PM
Revolvers leak gas from the cylinder gap. I think difference would be miniscule.

The Lone Haranguer
July 11, 2008, 09:05 PM
There are a lot of variables involved, but if you take, for example, a five-inch .45 ACP revolver barrel and a five-inch .45 pistol barrel, the revolver often gives higher velocity with the same load. Although some velocity is lost through the barrel/cylinder gap, all of the revolver's barrel is actual rifled bore, while the actual rifled bore length of the pistol barrel - whose length includes the chamber - is almost an inch less.

July 11, 2008, 09:18 PM
Remember that a 4" barreled revolver also has a couple inches of cylinder with the chamber in it. An auto with a 4" barrel has a 4" barrel with the chamber in it. True, the revolver has a bit of cylinder gap, but unless it's a huge gap, not much power is really lost.

Another thing to bear in mind is that two identical guns shooting the same ammunition may exibit different velocitys, with one gun averaging higher velocity than the other.

I have personaly seen a shorter barreled revolver shoot higher velocitys than a longer barreled revolver using the same ammo. Manufacturing variances I guess?

July 11, 2008, 09:41 PM
Velocities are not as consistant in revolvers due to differences in each cylinder. There is only one chamber in a semi-auto pistol. This also affects accuracy as well.

July 11, 2008, 11:05 PM
A .38 Special or .357 magnum revolver with a typical gap of 0.006" makes fore an area of escape of gas, all around, of about 1/15 of the area of the bullet. I guess that means 1/15 of the gunpowder is going missing that way. The magnum rounds leave the semi-autos behind. It takes a revolver frame to tame magnum energy.

July 11, 2008, 11:33 PM
Several years ago (could be as much as 25 years ago so details are vague) one of the gun rags tested this as best they could using revolvers and semi-autos with the same barrel lengths and ammo. They found that everything being equal, semis had more velocity.
However, as I understand it, all things are rarely equal (and yes, they did measure the barrel the same for both revolvers and semis.)

July 12, 2008, 12:17 PM
In the case of a recoil operated handgun the velocity loss due to operating the action is precisely equal to the velocity of the slide, cannon, or upper. This is easy to calculate and generally runs in the range of 10 to 20 fps.

In the case of a blowback or gas operated self loader, or a revolver's cylinder gap, it gets a good deal messier. For this purpose I would measure the barrel length of both revolver and self loader from the breech face.

I've done some experiments with a variable cylinder gap in the revolver with 44 Mag lite loads and 22 LR. The loss does not correlate in a linear fashion with the cylinder gap so it's not a simple case of saying the gap area is such and such a fraction of the bullet base area. The most significant point is not the velocity loss but that as the gap gets to around 0.012 the revolver will begin to spit crap back in your face.

July 13, 2008, 12:32 AM
Hmmm...So if I understand correctly, there's not much of a difference? It seems that's the over all vibe but not fully agreed upon by all?

July 13, 2008, 04:49 AM
Same round, I doubt you'd ever notice a difference. Revolvers however are the kings of Handguns as far as power goes. There aren't many .357Mag/.44Mag/454 Casull/etc in semi auto.

July 13, 2008, 09:20 AM
Bottom line: The difference in velocity isn't worth worrying about. Just get what ever flips your Bic.

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