People would probably be surprised to learn that a single manufacturer fabricates the bolts, and many other parts, for multiple suppliers of AR-15s.
That's why the "parts is parts" opinion exists.
https://customar15.net/ar-15-faq/bolt-carrier-group-get/While the industry has changed and expanded over the years and many companies are finishing receivers, making hand guards and turning barrels, there are still only a handful of companies actually producing bolt carrier groups.
This question comes up often. Here’s the short answer. Carpenter Technologies 158 alloy steel was selected as the ‘Mil Spec’ when the AR-15, chambered for the lower pressure .223 Remington round was upgraded to the higher pressure 5.56 NATO. This was many years ago and many things change in metallurgy as new testing, procedures and innovations come out. 9310 is a AISI grade of tool steel that is approximately 7% stronger than Carpenter 158 steel when heat treated and processed correctly. The companies we use have been in the business long enough to have seen both in action, and most are moving to strictly 9310, or using 9310 as a default unless specified.
Our thought on this – It’s much more important who made the bolt than the material used. Even if a new company called us and offered us BCG’s at $10 each, we would still stick with our contract shops we have dealt with for years. These are companies that produce BCG’s for the DOD as well as companies like Bushmaster, Stag, Armalite, Remington, LaRue, and many more. Rest assured when you buy a BCG from us, we will stand behind it 100% and you will simply be getting the best.
