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+--- Thread: Bolt Won't Go Into Battery (/showthread.php?tid=5456)
Bolt Won't Go Into Battery - tony549 - 04-30-2013
I'm assembling a Grendel upper with a 264LBC 18" long BHW barrel that I bought on sale last year. I checked with BHW to verify that it was made to accommodate the Alexander Arms bolt assembly before I got the bolt. I finally have all the parts and assembled the upper, but the bolt won't go into battery (rotate to lock up). I checked with a Colt AR15 bolt and it will lock up. The Colt bolt lug length is about 0.276 - 0.277 inch. The Grendel bolt length is 0.278 - 0.279 inch with a bolt face depth of 0.133 inch, measured with a Harbor Freight micrometer (uncalibrated). I'm wondering if the lugs are too long.
Bolt Won't Go Into Battery - Hobster - 05-01-2013
Man, I'd be weary of measurements made with anything by harbor freight. Harbor freight tools are cheap Chinese junk at best. I am no gun guru, but I have learned over the years, that a good tool (especially a precision tool) is worth the extra money.
Are your bolt lugs hanging up on the barrel extension?
Correct me if i'm wrong, but you could check this by measuring the distance from the front of your barrel extension lugs to the back of your barrel. If the measurement is less than your .278" , then you found the problem.
Like I said. I'm no expert, but it's worth a try! Oh, and use a quality mic to ensure accurate measurements!
Bolt Won't Go Into Battery - tony549 - 05-01-2013
I checked the Harbor Freight caliper against a Mitutoyo with a ball end and it seems good when comparing the thickness of a brass sheet in the same spot. Granted, my technique is nowhere close to that of a proper metrology SME. When comparing the AA bolt against a slightly worn Colt 5.56 bolt, the lugs are 2 to 3 mils longer. The 6.5G bolt will enter the barrel extension but can't turn. The 5.56 bolt will enter and turn to lockup. I'll try to see if a brand new NiB 5.56 bolt will go into battery.
Edit1: WMD NiB 5.56 bolt will not go into battery. The bolt will enter the barrel extension and butt against the rear face of the barrel, but it won't turn into lockup position. The NiB bolt lugs measure from 0.278 to 0.279 inch in length.
Edit2: The WMD bolt works fine in a Larue Tactical Upper. The BHW barrel is out of tolerance in the dimension between the barrel extension lugs to the rear face of the barrel. Drats, now I'll have to get the barrel reworked. No wonder it was on sale. I'll have to cross the vendor off my list.