Bolts and extractors?

[kcb38]

My apologies if this has been discussed recently but I was wondering if anything was going on with Monster bolts and / or the extractor group buy? I have a 12.5" upper build planned and would like to use the Monster bolt and maybe snag some spare parts. TIA

[Konocti's Wigwam]

My apologies if this has been discussed recently but I was wondering if anything was going on with Monster bolts and / or the extractor group buy? I have a 12.5" upper build planned and would like to use the Monster bolt and maybe snag some spare parts. TIA

Anyone know if the Monster bolts are DLC coated? I have some NB and Nitride BCGs but a DLC seems best.

[LRRPF52]

You don’t want too hard/brittle of a surface on bolts because it increases the likelihood of fracturing.

There’s a balance between surface hardness and ductility/core alloy strength, while being able to maintain dimensional uniformity.

After a series of bolt failures in the early 1960s, the USAF and Army did fleet testing post-production on early batches of AR-15s in the 1963-1964 timeframe when the bolts were still hard-chromed, and learned that hard-chromed bolts caused hydrogen embrittlement and early fatigue, especially with cracks at the cam pin hole walls, as well as bolt lugs shearing adjacent to the extractor pocket.

DoD changed the TDP by dropping the hard chromed bolt spec, going to manganese phosphated bolts for the Colt 603 (M16A1) and 604 (USAF M16) production, and retrofitted some of the Colt 602 rifles that originally had chromed bolts. Collectors later were able to get the complete uppers with chromed carriers, but phosphated bolts.

There’s a new liquid-burnishing process that increased bolt strength and doubles the bolt life for high-volume torture tested M4A1s, which elevated the average bolt life from 13,000rds to 26,000rds for the 5.56 carbines in their testing.