Bushmaster BAR-10
- SplineSpider
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Replied by mtrmn on topic Re: Bushmaster BAR-10
Perhaps everybody missed this statement in one of my previous posts?? I have used headspace guages before when I restored my grandfather's old US model of 1917 30-06 back to shootable condition. I will be checking the headspace, I just don't have any way of adjusting it if it's off-then it will be time to find a gunsmith for ARs.
I'm hoping that all the parts are held to a set of tight tolerances universally recognized by all the different manufacturers like the AR15 platform and nothing needs to be done. Right now just can't wait to get home in a week and get some hands-on.
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Replied by mtrmn on topic Re: Bushmaster BAR-10
OK, got the RRA BCG. First battle out of the rocks--I tear down both old Bushmaster and new RRA BCG's and compare parts.
The bolt carriers are basically identical externally. The staking on the gas key is professional and sufficient to keep the screws in place. Internally the only difference I found was a larger hole for the "tail" of the bolt to pass through.
The tail of the new bolt (which is what broke on my old one) is larger in diameter than the old Bushmaster. The new one measures roughly 5/16" in diameter and has NO groove around the circumference. The old one measures only 1/4" in diameter, and of course the groove is where it broke.
The gas rings are identical.
The ejector, spring and pin are identical, although the new spring is 1/8" longer due to compression of the old one.
The extractors are very different. The NEW extractor, spring and pin are the same design as the standard AR15, just twice as big. The spring has a black rubber insert.
The OLD extractor, spring and pin will NOT interchange with the new RRA.
I measured the length of the locking lugs and the depth of the bolt face on both bolts----they are identical in measurement.
The firing pins are identical, the firing pin retaining pins are the same cotter pins, and the cam pins are the same other than some wear on my old one.
The headspace gauges said the headspace was good to go, so I assembled the rifle, screwed on the suppressor and fired a few test rounds paying close attention to the brass for any pressure signs or headspace issues. All is normal. I will have to order some spare extractor parts for the RRA, but other than that the repair is complete and it should last me a very long time now.
IF it ever came down to that, I feel that I could drill the "tail hole"
in the old bolt carrier and use it with the new bolt. I don't know how hard that metal is though-maybe harder than a drill bit. And I can't foresee ever tearing up a bolt carrier anyway.
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