First off, I'm not a ballistician.. (and I don't play one on TV
)
I DO read a lot, though, and I've read some enlightening things lately on shooting cast lead bullets (boolits, if you prefer).
I will share them as I read them.. don't mean to start any shovin matches.
A gas-check is just what the name implies... it is a "check", or a stop, for the hot gases created when firing the cartridge. It keeps the gases from blowing past the base of the bullet, melting the lead as it goes. It creates a flat, consistent surface, with a good seal to the bore to accomplish that.
Leading is NOT caused by the base of the bullet melting. People have used "gas-checks" cut out of thin wax, then recovered the bullets with wax still intact, unmelted, on the base. If the gases don't melt the wax, it certainly won't melt the lead base.
Leading is usually caused by (1) gas blow-by (2) incorrect, insufficient bullet lube
Hardness of bullet alloy is not quite as important as most people think. Harder is NOT always better. Bullet alloy that is soft enough to allow bullet obturation (swelling to fit the bore) is highly desirable. If the bullet can't obturate, you get gas blow-by. Not good. Too hard an alloy is also usually too brittle to hold together for penetration, and will "shatter" or break up when hitting bone.
Like I said, these are just a few of the things I've run across that punctured a LOT of the "fact balloons" I'd been told as I got into shooting cast bullets.
Open for discussion...
