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Percentage Lost

Permanently deleted user
Anyone know what amount of energy, in percentage, is lost compressing the spring or blowback system in a semi auto pistol?

Also, metering out gas in other systems?

Sage 1
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5 comments

Date Votes
  • Tailgunner1954
    I've seen the data somewhere, at least for a gas system.
    IIRC the amount of velocity change from blocking the gas ports was less that the shot to shot variation in velocity (IOW the amount of change is lost in the noise of the system).
    If I had to guess, I'd say less that 1/10 of a percent (0.1%)
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  • Permanently deleted user
    Would that mean you would save only 1/10 of 1 percent in recoil? Does not seem the value of a muzzlebrake.

    Sage 1
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  • cpermd
    Muzzlebrake is completely different animal.

    CP
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  • givette
    The percentage lost is minute, indeed. In a M-14 system, the bullet is over one foot downrange of the rifle before there is any movement to the reciprocating parts. In an M1, the bullet is over three feet from the muzzle before any movement to the parts affected by the gasses.

    Can't speak of the pct. of loss in recoil operated systems (Lugers, US Army .45 autos, etc), but like the gas systems, the action remains locked until the bullet is gone from the gun also.

    Perhaps greatest loss (still small) occurs with blowback systems, where there is no locking to the action, and the spring must be used to retard the rearward motion of the bolt/slide.

    Bottom line: Percentages are small. Perhaps as little as 3pct in the blowback system, and that's the one that would use up the most energy. Best, Joe
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  • beantownshootah
    quote:Originally posted by Sage1
    Anyone know what amount of energy, in percentage, is lost compressing the spring or blowback system in a semi auto pistol?

    First of all, the first law of thermodynamics says that energy can't be lost, it can only change form. So the most technically correct answer to your question is ZERO.

    The energy used to compress the recoil spring isn't lost; its converted to potential spring mechanical energy, and then (when the slide goes back into battery) into kinetic energy. Along the way, you have further conversion into "lossy" (ie not easily harnessable) forms of energy like heat and vibration.

    Newton's third law (equal and opposite action/reaction) means that no matter WHAT system you use, SOME of the energy is going to get used up in recoil. There is no way around that.

    If some of the recoil energy were NOT used to compress the recoil spring, that same kinetic energy would be used to move the shooters hand backward in recoil.

    So in a very FAIR sense, the energy used to compress the recoil spring, isn't "lost" at all; its actually GAINED, since by recapturing some of it, you get the positive benefit of reloading the gun!

    I think a better way to ask this question is, "how efficient are usual semi-automatic pistols compared to other types of pistols"?

    I think, in fact, you'll find that in practice semi-automatic guns are usually MORE efficient than revolvers, since wheelguns bleed out propellant gas through the gun's cylinder gap, while autos don't.

    As mentioned, blowback guns are less efficient than locked breech systems, since the breech starts moving at the same time the bullet does, and the volume the hot propellant gas has to expand it is increased as the breech recoils, somewhat reducing overall efficiency.

    The most efficient guns would be locked/fixed breech guns, for example single shot "breakopen" guns, or lever or bolt-action rifle-like type repeaters.

    The next question is, how much more efficient are these? Depends on the exact system, but not that much more. In practice, the difference is quite small, and I doubt you'd see more than 1-2% more velocity from fixed breech guns of similar barrel length compared to usual recoil operated guns like 1911s.

    quote:Also, metering out gas in other systems?
    I think this is a more realistic question, since in these systems you really are directly tapping off some of the gas (energy) from the powder to cycle the gun at the expense of propelling the bullet.

    Even here, most gas systems are pretty efficient, and you don't get a big decrement in velocity. Also, most of them don't even start to tap any gas off until the bullet is well down the barrel, having already achieved most of its velocity.

    The best way to look at this in the real world is to compare the round in question from your gun, compared to the same caliber from a similar bolt action rifle. (Or you could use the same exact gun with the gas system blocked to compare against)

    Again, I think when you do this, you find that the difference in velocity is still small, still probably significantly less than 1-2%, and not a practical difference.

    quote:
    Would that mean you would save only 1/10 of 1 percent in recoil? Does not seem the value of a muzzlebrake.
    Whoa. . .time out.

    First of all, fundamentally recoil has very little to do with how the action cycles. Its mostly a function of the MOMENTUM (weight x velocity) of the projectile divided by the weight of the GUN.

    Next, muzzle brake has NOTHING to do with the action of the gun at all. It works by redirecting the venting gas from the barrel back at the shooter, somewhat counteracting the effect of recoil.
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