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6.8spc shotgun

rongrong Member Posts: 8,459
edited November 2015 in Ask the Experts
I just received thru a trade an AR15 in6.8spcII.
The rifle sprays bullets everywhere at 25 yds.
I've been trouble shooting the rifle and I've come
to look at the Linear Compensator which looks
like a 223 cal (even tho a 6.8 fires fine) .
I miked it and indeed it is not the correct size.
Can this be the cause of my accuracy issues?
Thanks
Ron
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    perry shooterperry shooter Member Posts: 17,390 ✭
    edited November -1
    YOU BET the last one inch or even 1/4 inch or 1/64 inch is the most important of the whole barrel Remove the darn comp. and try you may still need to REcrown the barrel to get it to shoot it is a wonder it did not blow the Comp off the end of the barrel if it is 223 Diameter
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    62fuelie62fuelie Member Posts: 1,069 ✭✭✭
    edited November -1
    If the inner diameter of the compensator is less than .280 it may well be disturbing the bullet's flight. If it isn't pinned or welded on, remove it and see if your rifle begins to group instead of throwing lead in the general direction you were aiming. If that is the case replace it with one of the proper dimensions. This can put quite a load on the rifle as the bullet has to swag down to the diameter of the comp before it can exit.
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    rongrong Member Posts: 8,459
    edited November -1
    a 30caliber bullet nose will fit down the hole
    of the comp I have.I wondering if the vortex of the
    gasses escaping destabilizes per each shot, causing the shotgun effect
    There are 2 designs of comp sizes :223 and 7.62,
    so the vortex must not be consistent in an
    undersized comp used on a larger caliber.
    I don't know.
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    charliemeyer007charliemeyer007 Member Posts: 6,579 ✭✭✭
    edited November -1
    What are you feeding it? Bullet weight appropriate for the twist. Was Rambo the previous owner that took great delight in rapid fire with out cooling and toasted the throat. Use a lens and a good light and look at both ends of the barrel.

    Clean the bore with some good copper fouling cleaner. Shooter's Choice works good for me. Run a really tight patch and feel for budges.

    +1 for try it without the compensator, and see if it's on straight. Use a V block and rotate the barrel looking for runout is a crude start.
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    rufe-snowrufe-snow Member Posts: 18,650 ✭✭✭
    edited November -1
    6.8mm is the Metric designation. For what we in the States call the 270. That has nominal bullet diameter of .277.

    I can't hardly believe that somebody mounted a comp, made for a .223 diameter bullet. On a rifle firing a .277 diameter bullet. But I have seen, stranger things!

    As the previous posters noted. See how it shoots with the comp removed.





    EDIT #1,

    The best way to measure the internal diameter of the muzzle brake. If you don't have dial calipers, with ID measuring capability. Is to use a drill bit of the correct diameter. A 9/32 drill is .282 in diameter. That would be the absolute minimum, internal diameter of the muzzle brake. Any smaller than that, and you would be in a world of hurt. Sooner rather than later.
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    62fuelie62fuelie Member Posts: 1,069 ✭✭✭
    edited November -1
    A 30 caliber bullet "nose" fitting in the bore of the comp doesn't tell you anything. A .30 cal bullet should pass freely thru a 7.62 comp - the entire bullet not just the nose. The function of a comp is not to impart spin to the bullet, that's done in the bore, it is to use the gases behind the bullet to compensate for the tendency of the rifle to rise in recoil by pushing on the baffles and venting the gases upward counter acting the recoil rise.
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    b0400879b0400879 Member Posts: 256 ✭✭✭
    edited November -1
    Take the abortion to a QUALIFIED AR15/M16 GUNSMITH for EVAL/REPAIR.
    Otherwise a sad widow will have to dump it upon the next victim.

    THIS quote could make for a fine epitaph.

    quote:Originally posted by rong
    I just received thru a trade an AR15 in6.8spcII.
    The rifle sprays bullets everywhere at 25 yds.
    I've been trouble shooting the rifle and I've come
    to look at the Linear Compensator which looks
    like a 223 cal (even tho a 6.8 fires fine) .
    I miked it and indeed it is not the correct size.
    Can this be the cause of my accuracy issues?
    Thanks
    Ron
    · Share on FacebookShare on Twitter
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