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Fixing my Bushmaster (and converting from A2 to A4)

Discussion in 'Rifle Country' started by MarineOne, May 30, 2009.

  1. MarineOne

    MarineOne Well-Known Member

    Hey folks,

    I've posted before about the shoddy warranty work Bushmaster did on my AR upper, so I'm putting together my parts list for rebuilding it and I figured I'd ask some of the harder questions now instead of later.

    My current parts list is below, since I'm going to reuse everything that won't need replacement:

    Barrel index pin
    Barrel nut
    New gas block with flip up sight
    Crush washer
    New Y Comp muzzle brake (replacing the A2 birdcage)
    Stripped A4 style upper (re-using the dust cover, forward assist, and BCG)
    Assembly manual and armorer's wrench
    Barrel vise blocks and action vise blocks

    So here are my questions:

    - I don't want to use Bushmaster for the parts, so where is there a good online source for them?

    - Will I need the gas tube wrench for removal of the gas tube on the old front sight block and install on the new one?

    - Can I reuse the pins from the old front sight block for the new one?

    - Am I going to need "Go/No Go" gauges once everything is back together?

    Thanks :)

  2. FlyinBryan

    FlyinBryan Well-Known Member

    the gas tube is hld in the front sight block by a small roll pin, so you will need a pin punch

    i have on more than one rifle without probs, but i also have spares here. its a good idea to have some just because they are so cheap.

    no, but they are nice to have around
  3. FlyinBryan

    FlyinBryan Well-Known Member

    oh ya, do yourself a favor and pick up a front sight base bench block and a taper pin punch.

    its a special punch with a semi-concaved tip that matches the head of the taper pins. it will save you from mushrooming the heads of the pins.

    and be prepared to hit them very hard. sometimes they are so tight you would swear they are welded in.

    the fsb bench block and taper pin punch will make a headache part of the job way easier.
  4. ARNETT44

    ARNETT44 Well-Known Member

    go to Brownells web site for the tools. The front sight pin is a real pain after the rifle has been fired much. You will need the block and the special punch without a doubt. Lining up the gas block can be fun so take your time.I have tried using a BB and also have done it by sealing the breach and blowing into the end of the barrel, while feeling the air out of the gas tube in the upper. But what ever works for you. Brownells also has many parts, but look into LaRue and I dont see it on the parts list but go with a free float forend. LaRue has and excellent one, while youre there anyway. Troy makes a good one as well that doesn't need the special tools. Anti seize barrel grease, strap wrench. Dont forget the locktite on the list.
  5. bkb0000

    bkb0000 Well-Known Member

    first off, post this same thread here: m4carbine.net

    then, get some new taper pins- at the least, they'll go back in loose, at the worst, you'll destroy them. 50 cents each at a hardware store, probably 2/0 size (confirm yours first, though)

    get a new roll-pin for the gas tube

    why barrel index pin?

    good luck
  6. MarineOne

    MarineOne Well-Known Member

    For the barrel index pin, I've been told its best to replace it when removing the barrel. I've got friends that are armorer's (Marine Corps, Army, and National Guard) that all have said just replace it so I won't have any issues.

    Searching Browell's site right now ..... I'll post more once I get the list more complete.

    Thanks again.

  7. kwelz

    kwelz Well-Known Member

    I agree with BKB. Post this question over on M4C. They are the best there is when it comes to AR15/M16s.
  8. MarineOne

    MarineOne Well-Known Member

    I checked out M4C and there is enough info over there that I found out what I needed to know and didn't even have to sign up.

    Thanks for the suggestion!


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