I have 2 bags of 50 of Talon Mfg. 643gr tracer bullets. I opened one package to inspect them and the other package is still sealed. These are new bullets and not pulled out of de-milled ammunition. $75 shipped for both bags.
I have some new, not pulled 690gr. ball projectiles left over form when I had a 50 BMG. These shot pretty good out of my bolt action 50 and were good for banging steel when I didn't want to use up my A-Max loads. I have a total of 150 bullets for $125 shipped.
I believe the weak part in the system is the bottom lug in the receiver. If you could make a model of that and run the test like you did on the bolt I would be interested in seeing what those results are.
John