Semi-auto power loss

This is a discussion on Semi-auto power loss within the Defensive Carry Guns forums, part of the Defensive Carry Discussions category; Using the same ammunition and barrel length, how much is lost in power going from a revolver to a semi-automatic pistol?...

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    Member Array Amnesia Wes's Avatar
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    Semi-auto power loss

    Using the same ammunition and barrel length, how much is lost in power going from a revolver to a semi-automatic pistol?
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    nearly a smidgen if any, that bullet is long gone before the bolt even opens plus revolvers have gas loss between the cylinder and barrel.

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    To the BG 10 feet away - none!
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    I would say not enough to measure. Especially if your on the recieveing end of things.
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    Of course there is loss. How much depends on size of cylinder gap. It could be a few fps or much more. However, it probably will not matter for SD applications.
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    Not that there's anything wrong with the question, but I am curious why you're asking?

    A number of things would come into play, as mentioned earlier, cylinder to forcing cone gap in the revolver, barrel length of the revo compared to the semi, and they are measured differently, type of rifling in each, how tight the barrel/lands are, and probably the twist rates of the barrels, and even how rigidly the shooter holds the guns.

    Again, just curious where this is going?
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    There are too many variables to categorically assert that the semi-auto will yield a lower velocity than a revolver. A semi-auto doesn't always give lower velocities.

    I've kept notes of handloads and chronograph tests for years and have tested a number of .45 ACP loads in both revolvers and semi-autos.

    Here's an example of a couple of different handloads fired in a Colt Model 1911 with 5-inch barrel and a Smith & Wesson Model 1917 with a 5 1/2-inch barrel. To eliminate one variable I've always used the same two handguns for all testing that goes down in the notes.

    Load: 185 grain cast lead SWC, 7.2 grains of Unique

    Colt Model 1911: 995 fps / Smith & Wesson Model 1917: 1020 fps


    Load: 230 grain round nose FMJ, 6.7 grains of Unique:

    Cold Model 1911: 871 fps / Smith & Wesson Model 1917: 830 fps

    Notice how the top velocity produced changed from one handgun to the other, depending on the load. This has been observed to be very common when testing loads in the two different handgun designs.

    Using the same load in two different guns of the same model and with the same barrel lengths can introduce velocity differences as significant as the differences observed in using a particular load in a revolver and a semi-auto. If I tested a particular load in any of my other 5-inch .45 semi-auto pistols I'd likely find one that gave a higher velocity variance than the revolver does when compared to test semi-auto mentioned above.

    None of the velocity differences, whether the revolver gives highest or the semi-auto does, could be said to be enough to represent any sort of meaningful "power loss."
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    Unless your running it through a chronograph, you'll never notice a difference.
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    Find two dirtbags who need 'shootin' (common defense statement in Southern courts..."Why? Cause' he needed shootin'."

    Have them stand side by side...using the same ammo, shoot one with the semi-auto, the other with the revolver. Then ask each what he felt. Errrr, never mind...

    , of course.
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    retsupt's been hittin' the eggnog today!
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    Quote Originally Posted by retsupt99 View Post
    Find two dirtbags who need 'shootin' (common defense statement in Southern courts..."Why? Cause' he needed shootin'."

    Have them stand side by side...using the same ammo, shoot one with the semi-auto, the other with the revolver. Then ask each what he felt. Errrr, never mind...

    , of course.
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    What's your formula or definition of 'power'? Where lies your belief there might be any "power" loss with a semi auto vs. revolver in the first place? Simple mechanics? Some semi-auto specific cartridges top revolver performance in the same caliber. Power is always relative and only part of an equation. In any equation there are two or more factors involved to produce an end result. In engineering terms there exists true power and apparent power especially in my line of work where electricity is involved. Funny thing about electricity and power and the relationship. No matter how much power is available, or how many amps one machine needs to run under full load.....electricity can kill you no matter what. At this point how much power is available at the circuit that causes your death is unimportant. Shocking truth.

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    Distinguished Member Array AKsrule's Avatar
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    Quote Originally Posted by Amnesia Wes View Post
    Using the same ammunition and barrel length, how much is lost in power going from a revolver to a semi-automatic pistol?
    Apples and Oranges....

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    Member Array Archie's Avatar
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    As it happens...

    This used to be a common argument, similar to the .45 ACP vs. 9x19 or .45 ACP vs. .357 Magnum argument. "Revolvers lose power in the cylinder gap" versus "Automatics lose power operating the slide".

    What is commonly ignored is the 'ballistics barrel length' which is the actual distance used to push the bullet. It is measured from the base of the bullet in the cartridge in the chamber to the muzzle. This is not to be confused with the holstermaker's barrel length, measured in autopistols from the breech face to the muzzle - longer than the ballistic length - measured in revolvers from the cylinder face to the muzzle - shorter than the ballistics length.

    It is hard to find an exact match for ballistics length between a revolver and an autopistol.

    In my own experience, I've chronographed the velocity of the same .38 Special wadcutter round in two autos (a Colt Gold Cup and a S&W M52) and several revolvers. The longest revolver had a six inch (holstermaker length) barrel. The two autopistols had the fastest velocities without question.

    Using a Hornady 148 grain HBWC and 2.2 grains of Clays, Remington cases and Winchester small pistol primers, here are the average velocities measured:

    Colt National Match: 727 feet per second.
    Smith & Wesson M52: 730.4 feet per second.
    S&W M15 (four inch): 704.9 feet per second.
    I cannot find the information for the six inch barreled revolver. (Sorry.)

    The two autopistols were measured with five shot strings; the revolver was measured with three rounds fired through each chamber (total of 18 shots).

    Please note this should be done with five or ten examples of each firearm to eliminate the test pistol being abnormal. I don't have that many. One also notes each chamber of the revolver - and revolvers in general with other models and other loads and calibers - shoots a slightly different average.

    It really doesn't show a whole lot of difference from my perspective. But interior ballistics is a fascinating field of study.

    This may or may not definitively answer the question for all time, but it gives a good answer for those three pistols and that loading.
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