Using 2 cavities of 4 cavity mold

[cabezaverde]

I have a 4 cavity aluminum mold that is cut for the same design. 2 cavities are plain based, 2 are gas checked.

Will it harm the mold long term if I only cast 2 of the cavities for an extended session or two? I use far more PB bullets than GC ones.

[high standard 40]

My experience only. I have a 3 cavity aluminum mold that is configured much the same as yours. 2 PB and one GC cavity. I have used this mold by filling only the desired cavities many times and have noticed no issues with my mold. My favorite mold is a two cavity iron RCBS mold which I use for my match ammo. The two cavities deliver bullets that are not equal in physical shape or weight so I use only one of the two cavities. Again, I have noticed no ill effects with this mold either.

[Dusty Bannister]

While I have no mold cut for two different bullets, and if this is a handgun caliber, have you tried the gas check bullets without the checks? Also, have you fired groups with the same powder charges with the different bullets to determine if there is all that much difference in the impact point on the target? I am just wondering how much difference if any, you might find to justify this practice.

[myg30]

Morning all. I have not had an issue yet with using two of 4. Aside from a few seconds to fill the other two cavs, return the others to the pot. Sell them ?
Dusty has a good suggestion above too.
Let us know how you made out for future reference.

Enjoy, be safe, Mike

[cabezaverde]

Bullet is for a rifle 311041 clone.

[Dusty Bannister]

Better yet for a 50 yard test. Plain based at normal plain based velocity, GC w/o GC, GC w/GC. We have a chance to really find something out here. Dusty

[popper]

No problem. Just poured the GC ones this morning in a 2 hole mold.

[earlmck]

I have a 180 grain LBT mould with the 2 & 2 configuration. For years I cast with just the two plain-based cavities because those are just right for my revolvers. Then I started shooting mostly with a 357 Rossi rifle and began using just the gas-checked cavities. Obviously no ill affects noticed. A while back I got a batch of the aluminum checks for plain-based and they work nicely in the Rossi so will now be using all four cavities.

In my revolver at 1200 to 1300 fps the gas check design w/o the check shoots just fine, but the crimp groove is placed a bit farther back and leaves more nose out for a longer COAL. Worked fine in Ruger but not quite as fine in the Colt so I stuck with the plain-base for revolver.

This has been my main 35 cal mould for around 25 years.