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AR-15 wont work 2

bambambambambambam Member Posts: 4,818 ✭✭✭
edited March 2013 in Ask the Experts
My barrel is chrome lined. So now what? Can't drill it?

I have a machinist drill index. These are all good bits, not hardware store junk.

Comments

  • rufe-snowrufe-snow Member Posts: 18,650 ✭✭✭
    edited November -1
    If you have sprung/bent the upper installing the barrel incorectly? By drilling a larger gas orifice hole in the barrel, your likely just going to screw the barrel up. It's usually done with EDM, because if you use a conventional drill bit it will cause a raised edge and burrs around the hole, that screws up the internal rifling in the barrel.


    Go back to square one. Get another upper and get the tooling from either Brownells or Midway, to do the job correctly. If you screw up the barrel you have now, your going to have to spring for another barrel, besides the upper.
  • bambambambambambam Member Posts: 4,818 ✭✭✭
    edited November -1
    I'm going to make a upper reciever block out of a piece of 1" stock when I get back from spring break.

    I'm not spending $40-80 for a piece of plastic that I may use 1-2 times.
  • M1A762M1A762 Member Posts: 3,426
    edited November -1
    How about buy the right tool for the job and sell it when you are done?

    Obviously anyone can slap together an AR.....or not.

    Live and learn.

    Or change your forum name to BubbaBubbaBubba!![:D]
  • bambambambambambam Member Posts: 4,818 ✭✭✭
    edited November -1
    Na, I'd rather make my own for free.

    That way I wouldn't feel bad loaing it to my brother. (probably never get it back, not much he has ever 'borrowed" has ever returned)

    I clamped the barrel in my v-block drilled the .057 port out to .073 one drill bit size at a time. I placed a aluminum cleaning rod inside the bore to prevent any burrs from forming. Worked really good.

    I'm going to take it out and shoot it in about a hour or so. Lets you all know how it turns out.[:I]
  • rufe-snowrufe-snow Member Posts: 18,650 ✭✭✭
    edited November -1
    quote:Originally posted by bambambam

    I clamped the barrel in my v-block drilled the .057 port out to .073 one drill bit size at a time. I placed a aluminum cleaning rod inside the bore to prevent any burrs from forming. Worked really good.




    If the gas pressure is to great because of the larger port size. BCG might cause problems do to much higher then normal operating velocity.


    Brownells sells a gas block that is adjustable, so that gas pressure from the port can be regulated.
  • MG1890MG1890 Member Posts: 4,460 ✭✭
    edited November -1
    It may not seem like much of a size increase (.057" to .073"), but you increased the area of the hole, and therefore the gas volume (and bolt velocity) by 60%. Be careful the bolt doesn't wind up stuck in your forehead!
  • Riomouse911Riomouse911 Member Posts: 3,492 ✭✭✭
    edited November -1
    Yeesh, this thread is reason #1 why I really, REALLY hesitate to buy a home-build gun, no matter how great the price.

    Lowers are a piece of cake to assemble because all there is are a few springs, pins, and trigger/hammer, especially if you have the vise-block to hold the lower. But the uppers may be tricky..especially if the vise blocks aren't used and improper torque is applied to the barrel during attachment. (In this case it might have ruined the upper receiver) When this happens things don't line up, tubes get bent, sights are canted, it doesn't run, on and on.

    BBB, I dunno man; if you're opening up gas ports another 25% (+/-) wider-than-factory-spec, I see a myriad of issues down the road..including constant malfunctions from timing issues, increased wear on gas tubes, other damaged internals such as BCG damage, rapidly sheared bolt lugs, extractor failures, on and on.

    As for the cleaning rod/"bore-burr" prevention, I am sure the aluminum rod fit snugly to the lands, but what about inside the rifling grooves? If not, the rod might prevent build-up on the flats (bearing surfaces) of the lands, but inside the grooves nothing is there to stop a ridge from building...until the burr ridge hits the surface of the rod (which is at land-height).

    I wish you good luck on this one, and hopefully I'm all wrong on it and it comes together for you. [8D]


    The gun now doubles on a single trigger pull? Run, don't walk, run to the nearest AR-15 qualified gunsmith and have it looked at. You're well on your way to a nightmare!
  • bambambambambambam Member Posts: 4,818 ✭✭✭
    edited November -1
    Spec on hole is .068-.090.

    It will fire now, but every 7-10 shots it double fires.
  • JnRockwallJnRockwall Member Posts: 16,350 ✭✭✭
    edited November -1
    i'd guess the problem lies in the buffer, spring, or tube.
  • bambambambambambam Member Posts: 4,818 ✭✭✭
    edited November -1
    I'll see if I can find a set of them "in stock" some where and replace them.
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