I have been using cast bullets with gas checks for a long time. It seems that there are 2 purposes for the GC. The first is to protect the bullet base from the effects of hot gas and the second is to scrape the bore somewhat since it is a harder metal than the lead preceeding it down the bore.
It will be interesting to see results of the testing you guys will be doing. I would like to know if the tape sticks to the bullet for it's complete flight every time or if it comes off all the time or part of the time. If it comes off that should affect the bullet's accuracy.
This is not entirely true. A bullet base needs no protection from gas and I know of no revolver that needs them because a PB bullet made hard enough will seal the bore. Bases do not melt.
The GC came about for shooting softer lead and should be considered a "skid stop." Soft lead forced to take the rifling will skid and if the base has the rifling marks opened larger then the rifling is, gas will squirt past, erode the bullet and deposit lead in the bore.
The GC will grab the rifling and halt any skid and leakage yet make the bullet too soft or fast and the GC will also fail so your gun will still lead up.
A GC will NOT scrape out leading but will just run over it. Experiments have shown the outside of a GC on recovered bullets to be badly leaded up and bores fouled badly with lead. A GC will seal gas but only by it's action as a "skid stop."
Putting thin stuff on a base can not do it.
By using a PB bullet of the proper alloy, I have taken the .454 to 55,000 psi with great accuracy, no leading and recovered bullets showed skid at the front half but it halted near the base.
Let me see if I can get a picture. This shows a .45 Colt bullet with no skid at all. Then a .475 PB with skid at the front but not at the base. It is very accurate and the barrels are clean after shooting them for two years without cleaning.
