Originally Posted by
gloob
I predict this will just mean he loses accuracy even earlier or at lower velocity. If the entire check is reaching melting temp by the time the boolit exits, I say it's due to a significant hot spot or leak on the rim of the check and his boolit is already suffered significant gas cutting down the side. I think the boolit would not be accurate by this point, even if you had the paper in there to prevent the check from melting off.
In my prediction, the base of bullet (as a whole, or on average) would stay a bit cooler, overall, due to this paper. But the gas check would get hotter, faster, because it can't share some of the heat with the base of the boolit, anymore. And the gas cutting down the side would be worse, i.e. it would become detrimental to accuracy at a lower velocity/pressure.
If there is no leak at all, the gas check should not get hot enough to melt the boolit. 2900 fps maybe changes that game of course! But we generally see boolit failure from the side. The base of the boolit doesn't melt first. The base is buffered by a boundary layer. Where gas jets by is much closer to max temperature, and all the time. So in my thinking, you could say the gas check is there to protect the side of the bullet by sharing damage control with the rest of the base.
edit: also just realized one potential reason a paper patch doesn't scorch or burn. It might ignite at similar temperature to melting point of boolit alloy, but it has to "cook" a bit before it burns. At that temp, the structures decompose first, before ignition. At high enough temp over ignition temp this might occur "instantly," but the surface of the lead will melt right as it reaches that temp and gets enough additional heat to phase change from solid to liquid, without any waiting. And with enough pressure and gas jet velocity, lead will perhaps get eroded out as it softens even before it reaches melting point.