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Thread: WTK: Muzzel velocity on 16"barrel HK94 vs handgun

  1. #1
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    Default WTK: Muzzel velocity on 16\"barrel HK94 vs handgun

    What is the muzzel velocity of an HK94 with the 16" barrel vs a handgun, say a SigSauer P226 or USP using the same ammo, say 115gr-fmj (NO + anything ammo please).

    I'm wondering if the 16" barrel gives you muzzel velocity benefits or is past the length of such benefit for a standard handgun 9mm cartidge. Would a shorter barrel actually give you the same or better muzzel velocity?


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    Default Re: WTK: Muzzel velocity on 16\"barrel HK94 vs handgun

    Well it's been a couple of days since this was posted and no one's took a stab at it. I was hesitant to because I don't honestly have any solid information to give you. However in the 1980's which was the hey day of the long barreled semi auto assault weapons I recall several gun magazines doing articles on them and it was repeatedly stated a few places that one benefit of the longer barrel with a 9mm round was that it brought it close to the same class as a .357 magnum. I've always wondered if they actually chronographed the rounds to see the velocity increase and compared this to rounds from a .357 revolver (no revolver barrel length was mentioned) Or if it just sounded good to them. At any rate if anyone here disagrees or has better information I certainly have no argument to make. In fact any of you with an HK 94 or an UZI carbine and a chrony might be able to develop some interesting conclusions I'd like to see after all these years.

  3. #3
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    Default Re: WTK: Muzzel velocity on 16\"barrel HK94 vs handgun

    Recently we were testing my friends new chrony and shot some subsonic 9mm loads thru 16" AUG and 10" UZI. We had some handloads and some factory ammo, and to our suprise the handloads vere slower in the AUG than in the UZI. Probably the "pressure curve" in my weak handloads was too fast (158gr bullet and fast powder, the guns worked though), causing the longer barrel friction to start slowing down bullet speed. The factory ammo was some fps faster in the longer barrel, as we predicted it would be.

    We are planning to shoot some 9mm loads thru chrony with an sbr in the future and compare the velocities with the ones from Glock 17 , if anybody is interested I can post the results.

    Trainer

    [This message has been edited by trainer (edited 08-18-2000).]

  4. #4
    dfs
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    Default Re: WTK: Muzzel velocity on 16\"barrel HK94 vs handgun

    some published figures for 9mm nato ball (115 gr):


    1130 fps 4.4 in barrel sig p220
    1200 fps 4.9 in barrel beretta 92
    1250 fps 6.75 in barrel walther mpk
    1312 fps 8.85 in barrel mp5
    1350 fps 10.2 in barrel steyr mpi69
    1370 fps 10.3 in barrel walther mpl
    1470 fps 11.2 in barrel czech m25

    couldnt find any info past 11.2 in but imho there would but no decrease in velocity (i would bet an increase).

  5. #5
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    Default Re: WTK: Muzzel velocity on 16\"barrel HK94 vs handgun

    Trainer, sure I'd be interested to see the results. And dfs those figures look pretty interesting.

  6. #6
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    Default Re: WTK: Muzzel velocity on 16\"barrel HK94 vs handgun

    So we still are not sure. I'd expect the velocities to increas as barrel length increases, as the figures posted by dfs indicate, but only to a point. The question is, where is that point. Anyone with a HK94 and a 9mm handgun have a chrono to try this on?


  7. #7
    dfs
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    Default Re: WTK: Muzzel velocity on 16\"barrel HK94 vs handgun

    my guess is that it would be at some ridiculous length. i saw an article once that tested your question but with rifles and rifle cartridges. i don't remember much about the article, but i remember that they concluded that it was a barrel that was way longer than anybody would ever carry (like 7ft. or something). i would suspect that the gains become trivial near the point where the bullet starts losing velocity i.e. add another ft. in barrel length and get 10 more fps. i would bet (and as trainer pointed out) that barrel, bullet, and powder tolerances from gun to gun and manufacturer to manufacturer play a greater role in small changes in velocity than barrel length. this also shows in my previous post where velocity gains are not an exact function of barrel length and no real formula for determining gains.

  8. #8
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    Default Re: WTK: Muzzel velocity on 16\"barrel HK94 vs handgun

    I'll agree that its a longer length, but I'm not convince dthat it would be some ridiculously long barrel for a 9mm pistol cartridge. For rifles, I can see that a 30" barrel or longer would proabably be the case, but the 9mm handgun cartridge was specified around a handgun with a short barrel. As such, why would there necessarily be enough powder charge to keep pushing the bullet faster in a 20" or 16" barrel when its mostly used in a 3" to 5" barrel? I would think a rapid burn to get up to max velocity in the initial couple of inches would be it... hence the question.

    Well if someone someday does this test, please restart this topic and post the results.


  9. #9
    dfs
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    Default Re: WTK: Muzzel velocity on 16\"barrel HK94 vs handgun

    the velocity will increase because there is still a considerable amount of force on the bullet even if the powder has completed burning in the barrel. ideally the powder charge should burn to maintain an even pressure through out the length of the barrel. once the powder stops burning the pressure does not go to zero, it just drop parabolicly (remember the gas laws)as a function of barrel volume.

    example:
    say a bullet is fired from a 5 in barrel. the ideal powder burn would increase pressure to the cartridges rated (say 30000psi) pressure and continue burning to maintain that pressure as the bullet moves down the barrel and the volume increases. lets say that we have an ideal powder burn and the 30000 psi pressure is maintained to the 5 in mark and the powder burns out but this time we are shooting it in a 40in barrel. at 10 in (volume at 5in times 2) the pressure would be 1/2 or 15000 psi. at 20 in it would be 7500 psi and at 40 in it would be 3750 psi and so on. your acceleration is decreasing but this is still a tremendous push on the bullet

    last the way that powder burns tends to produce more gas at the begining of the burn than at the end so it is difficult to maintain the maximum rated pressure toward the end of the barrel. this is due to a decreasing surface area of the flamefront on the powder. to compensate for this and maintain pressure pistols usally burn a tremendous amount (relatively) and burn most of it, at the reduced surface area, outside the barrel.

    i doubt anybody would be able to test this for you unless they have a really long 9mm barrel


    [This message has been edited by dfs (edited 08-22-2000).]

    [This message has been edited by dfs (edited 08-23-2000).]

  10. #10
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    Default Re: WTK: Muzzel velocity on 16\"barrel HK94 vs handgun

    Results of chrono is posted at http://ubb.hkpro.com/ubb/Forum7/HTML/000628.html
    mg42

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