|
Searching my archives (it's been a longtime since I used the 69BTHP/W748 load), the load was 26.5gn W748/69SMK/RP case OAL of 2.260. It was clocking an honest 2960fps from my Kreiger AR 20" and is .5gns hotter than Sierra lists as max. It's lots faster than Sierra claims in their manual. Using LC brass, I'd start at 25.0 seated to 2.260 and go from there. Book max for Sierra is 26.0gns for 2800fps. Case capacity is less for GI brass, but 1.0gn in a 223 is 5% right there and I'll bet that Sierra used GI cases or IMI because of liability. Either way, you should have zero problems. I've seen some INSANE loads shot from the AR with nothing worse than popped primers or primer pocket gas cutting where the case and primer come together.
Steve, I was pondering this WSR problem, and I'm betting it's a hardness issue with the primer cups. When they plated the cup, I'll bet there is some sort of hardening going on that the Winchester people didn't plan on(same way that nickel brass tends to split). The firing pin weakens the cup by creating cracks instead of a nice smooth cavity and the cup fails. That's my guess anyways. FWIW. S/F..Ken M
|