Bullets from pitted molds can be accurate if they fit

[higgins]

For many years now, I have shot 358477 bullets in a variety of .38 spl. and .357 revolvers. A while back I acquired a .357 Blackhawk with cylinder mouths that run .359-.360. My standard .38 spl. load is a 358477 of about .358 dia from a DC mold I've had a long time, unsized and tumbled in LLA.

My standard load wasn't shooting well in my BH. I bought a 358477 mold off of another website because the seller claimed it dropped a .359 bullet, and there was no rust in the cavities. It turned out that the diameter he claimed was correct, but both cavities had rust pits on one side near the bullet bases; it's the older style of 358477 with a longer nose section. I thought about trying to get my money back, but I didn't have much in the blocks and I knew the diameter it casts, so I decided to load them unsized and tumble lubed for the BH and give them a try.

It still didn't shoot as well as I hoped but they did shoot noticeably better than the .358 dia bullets. Other than the obvious conclusion that throat fit matters considerably in a revolver, there is also a lesson here if you obsess over having bullets that are "perfect". The pitted bullets shot better than "perfect" bullets of a smaller diameter. I've read that bullets with minor flaws shoot well, but now I've proved it to myself.

[runfiverun]

you could lap that pitted mold out a titch for a better fit.
you could fill in those pits with release agent and lap it out at the same time,
this would fix both issues.

[country gent]

I'm with RFR, I would lightly lap those cavities in that mould with a very fine abrasive. 800-1000 grit compound, Rubbing compound, Flitz, simichrome, or maybe even toothpaste. .0005 on a side removed will bring you to .360 for a better fit in the throats, and will remove the sharp edges and most of that pitting. Lapping is a slow process but can be very accurate and will help a mould in several ways, It does adjust size ( bigger only), it smoothes and removes burrs and surfaces improving bullets finish and release. It will improve roundness concentricity of the bullets, right now with the pitting on one side those bullets may not be as round as they can be.

[blikseme300]

Proper fitting boolits always perform best no matter how pretty the others may be.

Looking at the 1st pic I see that the rust is proud and is leaving indentations you described in the cast. I have thankfully not needed to restore iron molds but I'm wondering if naval jelly won't help removing the proud rust? I have used naval jelly on rusted rifles prior to refinishing with rust bluing to remove heavy rust with success.