Results 1 to 10 of 10

Thread: Velocity of M855A1 from a 20" barrel?

  1. #1
    Join Date
    Dec 2006
    Location
    Tennessee
    Posts
    9,201
    Feedback Score
    0

    Velocity of M855A1 from a 20" barrel?

    Googled it and can't seem to find an answer. I know what it does from an M4, but how about a rifle-length barrel?
    11C2P '83-'87
    Airborne Infantry

  2. #2
    Join Date
    May 2011
    Location
    ROCKET CITY, USA
    Posts
    3,606
    Feedback Score
    2 (100%)
    deleted.
    Last edited by Straight Shooter; 06-12-21 at 21:01.
    " Be NOT ye afraid of them..
    Remember the Lord, for He is GREAT & TERRIBLE!
    FIGHT for your bretheren..for your sons & for your daughters,
    for your wives & for your households"!

  3. #3
    Join Date
    Jun 2016
    Posts
    410
    Feedback Score
    0
    About 3,407fps from a 20" barrel. The info in the link shows an average velocity of 3,185 from a 16" barrel. Add 7% (M855 has a 7% higher velocity out of a 20" over a 16" barrel) for the additional 4" and you get 3,407fps.

    http://smallarmssolutions.com/home/the-m855a1
    Last edited by Red*Lion; 06-12-21 at 22:26.

  4. #4
    Join Date
    Dec 2006
    Location
    Tennessee
    Posts
    9,201
    Feedback Score
    0
    Quote Originally Posted by Red*Lion View Post
    About 3,407fps from a 20" barrel. The info in the link shows an average velocity of 3,185 from a 16" barrel. Add 7% (M855 has a 7% higher velocity out of a 20" over a 16" barrel) for the additional 4" and you get 3,407fps.

    http://smallarmssolutions.com/home/the-m855a1
    I have heard that M855A1 has a faster burning powder so that the 14.5" M4 has almost the same velocity as a 20" rifle (hence the higher pressures). If that is true then could it essentially negate what we would expect to be a rather significant increase in velocity going up from a carbine to a rifle-length barrel?

    That 3400-ish velocity you calculate would be awesome but I wonder if it is indeed the case?

    Also wonder if the rifle-length gas system tames the effects of accelerated bolt wear and gas port erosion from those higher pressures?
    11C2P '83-'87
    Airborne Infantry

  5. #5
    Join Date
    Feb 2016
    Posts
    2,338
    Feedback Score
    55 (100%)
    Extrapolating and guesstimating velocity is well and good, but you’d need to shoot and chrono to have an answer.
    3400 FPS from a 20” sounds optimistic as hell to me.
    A true "Gun Guy" (or gal) should have familiarity and a modicum of proficiency with most all firearms platforms.

  6. #6
    Join Date
    Aug 2017
    Location
    Lowcountry, SC.
    Posts
    3,552
    Feedback Score
    22 (100%)
    I’ve tested it in longer barrels. You’re not getting that velocity from a 20”, or perhaps anything.
    RLTW
    “Y-you realize that nighttime makes up half of all time?” -Rick Sanchez

    Disclosure: I am affiliated PRN with a tactical training center, but I speak only for myself.

  7. #7
    Join Date
    Dec 2006
    Location
    Tennessee
    Posts
    9,201
    Feedback Score
    0
    Quote Originally Posted by 1168 View Post
    I’ve tested it in longer barrels. You’re not getting that velocity from a 20”, or perhaps anything.
    Did your test include a chrono? If so what did you get?

    Also wonder, as I posted above, if the rifle length gas helps mitigate the higher pressure wear effect on parts.
    11C2P '83-'87
    Airborne Infantry

  8. #8
    Join Date
    Aug 2017
    Location
    Lowcountry, SC.
    Posts
    3,552
    Feedback Score
    22 (100%)
    Quote Originally Posted by ABNAK View Post
    Did your test include a chrono? If so what did you get?
    .
    It did. I cannot provide a number. I’d be cautious about the article posted above. It does not appear to be proofread very well, and contains info that was likely out of date at the time of publishing. It also includes the infamously over-hyped picture that older slide decks had. The author also did not sign his work.

    “M855A1 is at least an additional 200+ feed per second over the M855/M193 ball ammunition that the 5.56mm cartridge was designed around”.... oh, really? 200 more than M193, huh? Neat.

    Edit: just checked that thread where I ran it in a 16”.... 88fps over m855. 3400fps with an unleaded projectile is encroaching into 26” 22-250 territory.
    Last edited by 1168; 06-13-21 at 09:33.

  9. #9
    Join Date
    Dec 2006
    Location
    Tennessee
    Posts
    9,201
    Feedback Score
    0
    Quote Originally Posted by 1168 View Post
    It did. I cannot provide a number. I’d be cautious about the article posted above. It does not appear to be proofread very well, and contains info that was likely out of date at the time of publishing. It also includes the infamously over-hyped picture that older slide decks had. The author also did not sign his work.

    “M855A1 is at least an additional 200+ feed per second over the M855/M193 ball ammunition that the 5.56mm cartridge was designed around”.... oh, really? 200 more than M193, huh? Neat.

    Edit: just checked that thread where I ran it in a 16”.... 88fps over m855. 3400fps with an unleaded projectile is encroaching into 26” 22-250 territory.
    That was kind of the direction I was thinking in.
    11C2P '83-'87
    Airborne Infantry

  10. #10
    Join Date
    Sep 2007
    Posts
    3,227
    Feedback Score
    22 (100%)
    Quote Originally Posted by Red*Lion View Post
    About 3,407fps from a 20" barrel. The info in the link shows an average velocity of 3,185 from a 16" barrel. Add 7% (M855 has a 7% higher velocity out of a 20" over a 16" barrel) for the additional 4" and you get 3,407fps.

    http://smallarmssolutions.com/home/the-m855a1
    Yeah no.

    This guy is getting 3159 fps from a 22" bolt action, so I dont know what kind of crack he's smoking getting 3400 fps.




    Quote Originally Posted by ABNAK View Post
    I have heard that M855A1 has a faster burning powder so that the 14.5" M4 has almost the same velocity as a 20" rifle (hence the higher pressures). If that is true then could it essentially negate what we would expect to be a rather significant increase in velocity going up from a carbine to a rifle-length barrel?
    I wish such a magical pixie dust powder that gives almost 6" worth of barrel velocity existed.
    Last edited by vicious_cb; 06-13-21 at 22:07.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •