Yaaa grandpops, there are a few of us cheap, miserly types that shoot lead in guns that really need a good jacket bullet. I've been shootin' lead thru my .30-30s' .300Sav. and .30-40 for over 60 years I do have 8 differant bullet mould just for the .30s' and with the exception of the 130gr, that I use in my .30 carbine, all are gas checked.
When ya just like to shoot, weather it be a grey digger, deer or bear, ya try to use the cheapst method. Ya gotta realize, back in the '50s--'60s, a good quality jacketed bullet figured out a smidgen over 3 cents a piece. Lotta money for a youngster tryin to raise a family!
Indeed Dale, the base of a gas checked bullet does have a smaller base just for the purpose of crimping on the gas check, and when properly resized, the gas check are is the same dia. of the bullet body.
In my experments, I have found that I can load up to 2200fps, before I start noticeing any signs of heat distortion, on a gas checked bullet. However, once I exceeded 2200fps, the distortion rapidly got worse.
As heat starts to melt the lead(The distortinon I mentioned), the lead will become a vapor, as that vapor excapes down the barrel, it will again solidify, normaly on the lands between your rifleings. I assure you, it is not an easy job to get that lead out, once ya get it in there. Your best bet is to be carefull and do not exceed that magic number of 2200 fps, in my cases!
To this day, my wife and I still shoot primarly lead, and we do get a average of 4 deer a year. we do probably shoot well over 1500 rounds a year, just becaus we like to shoot!