We have good banter here on this forum; if I don't agree or have a difference I will always try to explain why. I have a great deal of respect for everyone on this quieter forum. If I'm full of horse manure I can live with being wrong.
I agree, barrels can be a law unto themselves. I shoot jacketed stuff with cast all of the time from several rifles. I don't clean them much unless its humid because they really don't foul much.
If a barrel copper fouls or in fouls certain places, its going to foul with cast in those same areas, usually worse, even when clean. Copper fouling is there because of friction, pressure and finish, but lead fouls because of gases? Copper layering produces a rougher on an already rough finish, so yes I agree, its going to mess with a cast bullet which needs to have a seal for support and needs a smoother, more even finish.This is the contact area that makes the gas check help.
A loose core or one that is distorted beyond its strength within a jacket will become molten without contact from hot gases in the same way it does in a barrel. The snug fit is for support and balance and to minimize heat from moving under stress at its weakest contact area, just like it is in a core.
It is also always not true that they need to be .001 to .002 over or not slightly undersized to not lead or work. This is why many like softer alloys because the base can bump up and create that seal and base support. Elmer Keith touted "exact groove diameter" for sizing cast bullets, but he got around leading (we think) by using soft enough alloys and pressure within the limits of the alloy and lube. The old outside lubricated Colt rounds with straight chambers needed hollow based bullets and soft alloys or they were flat dismal, but they worked despite being undersized on purpose.
But agreed, starting off with a snug fit makes life much easier. But even when you have even an oversized bullet you will still see a recovered PB bullet with distortions at the very edge of the bullet base where stress is the greatest and on the leeward edges where rifling is engaged, despite having plugged everything up.
If lube runs out you will also see leading even with a gas checked bullet, often at a rifle muzzle, despite having sealed off all of the gases and the lube. The lube's ability to do its job doesn't expire from hot gases, its expired by friction.
Another explanation is high temp grease, wax paper fillers,dacron filler,card wads, fiber wads,plastic shot buffer filler for a bullet base.
Every one of these items will burn up on top of your lead pot way before your pot is close to being molten, yet every one generally exists when fired pretty much in the state they started in the case, despite being exposed to gases that that are hot enough to supposedly melt lead.
We use these items to move the stress area at that base edge, to cut down on the pressure and friction lead is exposed to on that base edge, just like a gas check. I still question the notion we use them to keep the base from melting due to gases.
Sorry fellas, I don't care about the SB today!
