Miale has it right on all counts. The added radius at the lugs is a common sense improvement guaranteed to reduce stress concentrations. Dcmdon is right too: finite element analysis results will light up dangerously high stress concentrations at the lug root in blazing red. The careless omission of this radius in the mil-spec design needed to be corrected.
But what's even worse is the undercut at the lugs combined with the cutout at the bolt face to accommodate the extractor in the mil-spec design. This is an especially amateurish error that shouldn't have made it to prototype testing. That improvement alone makes the LWD product superior, and worth the extra cost, IMO. The mil-spec bolt design is like rotors and points and carburetors in an IC engine. We were satisfied with them when we didn't know better and had no other choice. They worked OK, but not all that well, and you always had to rebuild or replace them. Why settle for old, less-reliable technology when there is something better? Nostalgia?
LWD has a white paper describing the improvements to their bolt that I would post to the forum if I could, but the file is too big. Contact
info@leitner-wise.com and ask for the PDF of the HPB Development White Paper if you want something in writing instead of just hot air.
Several have made claims that AISI 9310 has problems. Maybe it does. But it is a fact that 9310 is the most frequently used steel alloy for aircraft gears. If you have ridden on an airplane, commercial or military, you have placed your life in the hands of an engineer that specified 9310 over all other steel alloys available at any price. How did that work for ya? Did those nasty "tramp elements" cause you any grief? Did your helicopter fall out of the sky when a 9310 component in the power linkage failed? Did the landing gear on your 747 fail to deploy due to 9310 metal fatigue?
Mil-spec strategic materials have their place, especially when the law demands that the lowest bidder wins the contract. But I don't trust any government bureaucrat (and that is who defines mil-spec, not the Army, Air Force, Navy, Marines or Coast Guard) to make the wisest decision for the gun parts I buy. And I sure as hell don't trust a bulk steel manufacturer to recommend the absolutely best material for a very specific application when he can rely on a military specification to compel the purchase of an antique alloy that he can sell at artificially inflated prices and one-ton minimum quantities. I've dealt with steel manufacturers my entire career. You can't count on them to sacrifice a single penny to help you out. It just isn't in their nature.
That said, will someone show me a destructive testing study of a sample of identical AR15 bolts made from 158 and AISI 9310 subjected to identical loads under identical conditions? Them's is apples to apples.
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