450Bushmaster.net

So if the bolt is rated for .22-250. Which is on a .473 case head. And SAAMI spec's at 65k psi. I don't understand how people break bolts. I could see if you are opening the bolt face on a standard bolt, or running a factory 450B bolt spec'd for 38.5k and you then run 55k or 65k loads.

Bolts are disposable items. It may be rated for a certain pressure, but for how long? You also have case geometry playing a role, and if the chamber or cartridges have any oil or polish in/on them. You have different metals being used, and if the company properly hardened or treated. Are you constantly running the upper end of pressure, or exceeding it, all the time?

A lot of things come into play, concerning bolt life. For the most part, if It’s not 5.56/.223 based, don’t expect the bolt to last as long, even if it’s a beefed up version. If it holds up as long, congrats. A bigger bolt will hold up better, a bigger bolt and barrel extension (won’t fit typical AR uppers) should do just fine. But you will eventually lose a bolt, even in 5.56/.223.

I completely understand that they are disposable items. Over a long enough timeline every machine component has a lifespan. but saying a bolt is rated for 65K and then it breaks 100 rounds in of 60k handloads means either the part is bogus or your handloads arent 60k. Bolt life should be measured in 1000s of rounds not 100s.

Things can happen, and some bolt's break. I had a 450B bolt crack in less than 100 rounds, and I was just starting to lean on it . It was supposedly 9310, which when treated properly, is stronger than Carpenter. I have 2 Carpenter 450B bolts, that I have pushed harder, and for a lot more rounds, they're still holding up. If your upper is a bit out of square, you can take a bolt out quicker, or take it out of spec where it won't work anymore. As to the Oly bolts, I wouldn't trust there 22-250 bolt to last a long time at 65K. 1-2000rds, maybe 3-4000rds. Wouldn't surprise me if they figure you'll burn the barrel out of that 22-250 before the bolt breaks, so your fine at 65K, when really, you probably aren't. Hell, look into some of the WSSM uppers. Some guys had their upper's grenade, I know a couple were stuffed into standard AR uppers, but I want to say a couple utilized a special upper with bigger bolts and bigger barrel extensions. So, yes, some companies rate things to levels that shouldn't be pursued.

In my opinion, an oversized bolt in a standard AR upper is pushing the limits at 60K. So far they seem to be holding up just fine. If you try going to a 450B case, I wouldn't worry about bolt thrust and bolt life so much, but as you mentioned earlier, the barrel tenon.