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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
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
