02-06-2012, 06:55 PM
I looked at the SCAR-Heavy bolt in 7.62 NATO, and they used a much smaller bolt design than an AR10. They use some type of steel that appears to have a higher Chromium content, but I don't know which one-looks like 9130 to me, and several metallurgists have listed Carpenter 158 as the better alloy for AR15 bolts compared to 9130. I talked with Bill A. about this in some detail at SHOT, and he pointed out how 9130 has sulfur content in it, which is by no means a high-strength element.
The word is that FN has experienced several endurance failures with their SCAR-17 7.72 NATO bolts, which is what that bolt was screaming into my face when I looked at it personally. "I WILL BREAK! I WILL BREAK!" That is what I heard it literally saying to me...
The Milspec Colt 5.56 bolts take an insane amount of abuse, and hold up very well, even though I feel that the AR15 bolt geometry in even a 5.56 is on the risky side of low-mass, barely supported lugs, and definitely a cam pin hole that has hardly any support.
None of these are true with the original AR10 7.62 NATO bolts. The AR10 takes a beating and asks for more.
The word is that FN has experienced several endurance failures with their SCAR-17 7.72 NATO bolts, which is what that bolt was screaming into my face when I looked at it personally. "I WILL BREAK! I WILL BREAK!" That is what I heard it literally saying to me...
The Milspec Colt 5.56 bolts take an insane amount of abuse, and hold up very well, even though I feel that the AR15 bolt geometry in even a 5.56 is on the risky side of low-mass, barely supported lugs, and definitely a cam pin hole that has hardly any support.
None of these are true with the original AR10 7.62 NATO bolts. The AR10 takes a beating and asks for more.