Filthy 14 had a bolt that lasted 30k and still going. First one broke at 16k. Gun has near 50 or so I thought to date.
Printable View
I agree. That's a lie by Tom. No other way to say it. I MIGHT believe it if he were running the bolt in a quality barrel with a rifle-length gas system, true 5.56 NATO chamber, the Vltor A5 system with an A5H3 or H4 buffer, and an LMT E-carrier (all of which reduce stresses on the bolt).....but using a std carrier design with a pistol gas system and the carbine buffer system? Nope. I just don't believe it.
Note: I run a Spikes lower for my patrol carbine, so I'm not shitting on spikes...but it's claims like this that make it difficult for us to take some of his legitimately decent products seriously. That and he copies other company's design like MOTHER RUSSIA in 1965. ;)
As far as I know, no one's broken an E3 bolt yet. I wonder what the highest round counts on those are.
The biggest benefit I see from using S7 is the higher tensile strength which translates to a higher endurance limit - the number of loading/unloading cycles the bolt can handle before it fails. However, cjb makes some good points about the nuances of steel selection. There is also a lot to be said about how the grain structure affects the performance of steels.
Heat treating is another animal. As mentioned it needs to be considered whether case hardening or through hardening is desired. I'm willing to bet that an AR bolt has different hardness requirement at different locations. Given the differences in section thickness between the body of the bolt and the lugs, for example, I'd be surprised if AR bolts are heat treated in a single process. Tool steels also need to be heat treated in a vacuum or in the presence of nitrogen or some inert gas or else they will be decarburized. Some steels are more dimensionally stable during heat treatment as well but there is almost always finishing operations needed afterwards.