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Posted: 4/15/2009 8:50:09 AM EDT
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Last fall I bought a Bushmaster bolt (not carrier, just the bolt assembly itself) for a spare.
The description on brownell's website says: Bolt and carrier assemblies provide smooth, efficient cycling and improved reliability in any AR-15 application. Precision machined from the highest quality ordnance-grade steels to current military—or higher—tolerances, then hardened and magnetic particle inspected to ensure there are no microscopic cracks or flaws that could lead to premature failure. Bolt made from high-strength Carpenter 158 steel alloy is heat-treated for exceptional surface hardness to handle the battering of thousands of cycles. Includes extractor, gas rings, ejector, pins, and springs. Carrier of 8620 steel is chrome lined to ensure smooth bolt function and superb wear resistance for years of reliable service. Comes with chrome-lined carrier key installed.
The bolt has 'CM' stippled on the body, upside-down. What does this mean? How good are Bushmaster bolts? Are they batch-tested and all stamped, or are they all MP tested? (Yes, I checked 'the chart'. I know what it says - I'm just looking for any firsthand info here...) |
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I was always under the impression that 'CM' denoted Continental Machine aka CMT. They supply components to many AR manufacturers and are good to go. To my knowledge, they do their magnafluxing in-house.
I've never had an issue with a Bushy bolt, and I own several of them. Coming from me that's fairly high praise-since I'm one of those nutcases who think nothing about spending twice as much for a genuine Colt bolt 
I have several brand new Colt BCGs in the wrapper, ready for installation when/if a Bushy bolt fails. That said, I haven't had to replace one yet that didn't have an extremely high round count. Like a Colt bolt, a Bushy bolt will show excessive wear when the locking lugs start to fail. This is far different than DPMS bolts, for example, that tend to break at the cam pin hole. Like every manufacturer (Colt included) there are bad apples in every barrel. While I've had other QC issues with Bushmaster, their BCGs have always been good to go-at least for me. Hope this helps 
ETA: Beaten AGAIN! |
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Quoted:
Thanks guys - that's all I wanted to know. The hard part is that having a spare bolt makes me want to build an upper around it. 
 That happens to me all the time. I'm a firm believer in having a pile of spare parts around. Those parts tend to attract themselves to one another...and become rifles
It's some sort of magnetism in the metal, I think. |
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