45 Cal GC ?

[GONRA]

Like many others out there, GONRA uses Lyman 452374 for .45 ACP "GI ammo".
If that casts too phat, use Lyman U 452374.
REALLY wanna use a gas check? Use Lyman 452484

Maybe ya can't get these moulds any more, but ya could in the "Good Olde Days".

[Good Cheer]

One of the least used and the most reliably feeding and expanding .45ACP loads is a gas checked "GI" round nose that has the mold given a huge hollow point and cast really soft. Mine is a #452484 from the early eighties when Lyman did a sell off of molds that their equipment let the cherries be slightly deeper into the blocks than QC allowed. Think I paid five bucks for it. Made 248 grain slugs before it was hollow pointed.
The gas check is there to give the boolit a little extra structural integrity and assist in preventing lead build up. The nose contour helps it feed reliably when your pistol isn't professionally polished up. It doesn't need high velocity to pop open like a drag chute. The weight is there for not being finicky going from clip to chamber and for the expanded boolit to push on through whatever meat gets in the way.

[Rapier]

The 45 ACPs handguns by and large have very shallow groove barrels for jacketed bullets. They will shoot cast fairly well if the bullets are fairly hard and have sufficient bearing surface. Otherwise, in my experience, garnered over 60 years of shooting competition, soft bullets tend to skid over the sallow lands.

My competition 45 ACP guns all have barrels with cut rifling .004 deep, specifically made to shoot cast bullets. I use the hard cast 230 grain bullets of the truncated cone design, I gave up on the 230 RN moulds with standard ACP barrels.

I also use the Lyman 45 Auto Rim 236 SWC plain base bullet mould, no longer made by Lyman, for pin competition and the 200 H&G plain base hard cast for IPSC. That 236 bullet casts at 252 grains, is a plain base. These are all .452 bullets and use .452 groove barrels.

My .458 bullets for the .458 barreled rifles use gas checks as they regularly produce velocities well over 2,000 with lubed bullets.
However, with PCed bullets It is not necessary to use GCs with a plain base, if the bullets are placed and baked nose down, in a hardware cloth box, with the base coated.

I use the same process with the RCBS 200 grain FN 358 plain base bullets, double powder coated without any gas checks for use in my 358 ARs, two, at 2,400 to 2,500 fps without fouling, at .4 inches at 100. Only mentioned because of the gas check question and the lack of need for them.

If you can powder coat, using the shake and bake method, there is very little reason to use a gas check at all even with velocities up to 2,500 fps. I stopped pursuing higher velocities at 2,500 when I found the accuracy and velocity I was seeking. However I believe a bit higher velocity over 2,500 fps is possible, right up to a point is reached where the friction melts the lead projectile. But you do need the land height or groove depth, same, same, to support the cast bullet's velocity for accuracy.