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New AR Barrel!

Discussion in 'Maintenance & Gunsmithing' started by ZigZagZeke, Jun 5, 2012.

  1. ZigZagZeke

    ZigZagZeke Eugene Silver Supporter Silver Supporter 2015 Volunteer

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    So you might remember that I sent my Bushmaster Varminter with the 24" chrome moly barrel in to Bushmaster to be diagnosed for accuracy issues and rebarreled with a stainless barrel. They found that the last couple of inches of the old barrel were pitted. A big clue was an uneven fouling pattern on the muzzle.

    The former owner swears up and down that it was shooting great groups when he sold it. I've put about 200 rounds through it and never gotten better than a 4" group at 100 yds from the bench. I'm not the issue. I shoot 3/4" groups with my Howa .30-06 at the same range. I changed scopes after I found that the tube was loose inside the original (how it shot "great groups" with a broken scope I don't know), changed ammo, changed shooters with no improvement. So when Bushmaster found the pitting I was actually relieved.

    So there it sat at the Bushmaster/Remington repair shop since last October. After about 90 days of "back ordered" status I went searching for a barrel myself, and sure enough, they weren't lying when they said there were none to be had. Well, last week I finally found an "in stock" Wilson, 410 stainless, 24" bull barrel chambered for both .223 and 5.56 at Fulton Armory, and it was about $50 less than Bushmaster had quoted me, so I grabbed it. I waited until I had a barrel and a .936" gas block to fit it in my hand, and today I called Bushmaster and told them to send my rifle back to me.

    I have the receiver and barrel blocks, the right pin punch, a barrel wrench, and a torque wrench. I know how to do this. But I do have a few gunsmithing questions:

    Bushmaster uses semi-permanent Loctite to cement the gas block onto the barrel. I have a bottle of it. The stainless steel gas block I got has two allen head set screws for mounting it. I prefer the Bushmaster Loctite method for a lot of reasons: accuracy (no stress on the barrel from the set screws, neatness, permanence (the Loctite is NOT going to work loose over time), etc. I can't think of any good reasons to use the set screws except ease of removal. Is there ever a time when you would want to remove the gas block from the barrel? What's the best way to make sure I line up the gas port in the gas block with the gas port in the barrel? Am I going to have to make any changes to the gas tube? Would Fel-Pro N5000 be a good anti-seize to use on the barrel threads? I've heard torque settings from 50lbs to 80lbs to "real tight". What's the best way to torque the barrel nut and what spec does everybody use?

    Fel-Pro PRODUCT DESCRIPTION
    N-5000 is a nickel-based anti-seize lubricant,
    produced under 100% controlled conditions for highest purity.
    It is formulated to have the lowest practical levels of halogens,
    sulfur and heavy metals, including copper. N-5000 has a
    general composition of nickel and graphite flake in petroleum
    carrier. All ingredients are selected for extreme purity.
    Special Features:
    · High purity - made from highest purity ingredients
    · Trace amount of copper - less than 50 ppm copper
    · Typically used in applications with a dry surface
    temperature of -29 to +1315ºC (-20 to +2400ºF)
    TYPICAL APPLICATIONS
    · Bolts, studs, valves, pipe fittings, slip fits and press fits in
    nuclear electric power generating plants, chemical plants,
    pharmaceutical plants, paper mills and other locations
    where stainless steel fasteners are used.
    Operational Benefits:
    · During assembly - prevents high friction, galling and
    seizing.
    · Promotes uniform and predictable clamping.
    · During operation - high purity prevents stress corrosion
    · Disassembly - prevents seizing, galling, destruction of
    threads
     
  2. Stomper

    Stomper Oceania Rising White Is The New Brown Silver Supporter

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    The barrel should index when you insert the extension into the receiver. When you place your receiver in the vice use a level to make it level left to right and front to back. You can then install the gas block and use a level to make it level, then you know it will be lined up with the receiver properly.

    Hope that makes sense.
     
    Varmit and (deleted member) like this.
  3. deadshot2

    deadshot2 NW Quadrant WA State Well-Known Member

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    I use compressed air. Set the regulator down to 4-5 lbs, plug one end of he barrel and insert a tube wrapped with vinyl tape into the other. Hook up air hose and then align the gas block for maximum air flow. A quick marking of he bbl with a scribed line and an index mark on block and barrel allows for future removal/reinstall without having to use this method again.
     
    Varmit and (deleted member) like this.
  4. ZigZagZeke

    ZigZagZeke Eugene Silver Supporter Silver Supporter 2015 Volunteer

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    Wow! Thanks, I didn't think of that. I used to be an instrumentation tech, so I have a couple of air flow gauges in my toolbox. It would be a snap with the air supply line running through one of those. Much better than eyeballing it.
     
  5. ZigZagZeke

    ZigZagZeke Eugene Silver Supporter Silver Supporter 2015 Volunteer

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    OK, so the rifle arrived on UPS today. Remington/Bushmaster didn't charge me any shipping or any other charges for keeping my rifle for 8 months without doing anything to it.

    I pulled the old barrel and installed the new one. One thing that I didn't see mentioned anywhere is that Bushmaster uses permanent Loctite on the gas tube/gas block junction, in addition to gluing the gas block in place on the barrel with it. After removing the roll pin I used my propane torch to heat up the gas block and remove the gas tube, then I removed the gas block so I could get the barrel nut off and re-use it.

    Anyway, the new stainless bull barrel is installed and everything looks good. I didn't have to adjust the length of the gas tube or anything like that. I torqued the barrel nut to 50 lbs and then tightened it enough from there to line up the gas tube ports on the next hole.

    One tip on the Varminter free floating hand guard is that I used a piece of thick saddle leather with the rough side against the knurled finish on the hand guard and an 18" pipe wrench on the leather to gently loosen and tighten the hand guard. I have both the receiver and the barrel clamping blocks, and I can't imagine trying to do the work without them. Those and a good propane torch are a necessity.

    I'll report on the barrel and accuracy when I get a chance to fire it.

    I want to have somebody check the old barrel and see if shortening and re-crowning it will produce a good 20" barrel. And BTW, there is definitely a nick on the inside edge of the crown on the old barrel at the 12 o'clock position. I was finally able to see it with a good light and a good magnifying glass this evening. Still debating whether to have it threaded for a flash suppressor/muzzle brake (primarily for cosmetics) if I shorten the barrel.
     
  6. mjbskwim

    mjbskwim Salmon,Idaho Well-Known Member

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    Find someone with a bore scope to inspect the bore and tell you where to dock it off at.
    Should have at least one smith around with a scope,no?

    Hawkeye BoreScope
     
  7. ZigZagZeke

    ZigZagZeke Eugene Silver Supporter Silver Supporter 2015 Volunteer

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    Well, the new stainless barrel is installed, the new scope and mounts are installed and bore sighted. I'm ready for the range now. I really, really like the cheek weld and site picture now. I got a Burris PEPR cantilever mount and put it right on the receiver without the stock riser blocks. Only thing that crossed my mind is I'm not sure I like the shiny white stainless barrel on a coyote rifle. Is there an easy method for coloring the stainless barrel? Can I do it myself?
     
  8. deadshot2

    deadshot2 NW Quadrant WA State Well-Known Member

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    There are numerous products that you can use to cover the shine of the stainless barrel. Brownell's Alumi-Hyde II is one of them that doesn't require baking. Degrease well and paint. Will give a finish much like that on most scopes. You can also use what some call "Poor Man's Ceracote" which is the high-temp exhaust paint available at most Auto Parts store. If you degrease the barrel well, the paint will hold up far better than one might think. How well it holds up will depend on how rough you are with your rifle. Shooting coyotes is far different than dragging a rifle around in some far away place shooting "Jihadists".
     
  9. ZigZagZeke

    ZigZagZeke Eugene Silver Supporter Silver Supporter 2015 Volunteer

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    Dropped it off at Allison & Carey today to be shortened. They said they think it only needs to be shortened about 2" and they'll put an 11 degree target crown on it.