Long before the internet, I started casting. Had to rely on published recommendations from the manufacturers of reloading/casting equipment. Mainly, RCBS & Lyman.
Back then, reloading suppliers, like Mid-South & Natchez, put out catalogs. In those catalogs were reprints of RCBS's products. There use to be charts with bullet moulds offered, sizer dies, & top punches..............including part numbers and recommended sizing die selection.
Today, I was going through my old literature and found such chart in a 1984 RCBS catalog.
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All across the board/chart, RCBS recommends sizing to
nominal jacketed bullet diameter.
No wonder their bullet moulds tend to run small. Fine, if you can get away using that size bullet, I rarely can.
Let's take 44 Magnum. A .429 diameter sizer is the specified. Now, if you look at the chart in the bottom left of the page, they list .430 & .431 dizers, as alternates. Now if you need .432, .433 or .434 for your Marlin or revolver with oversize throats, your SOL. Remember, this is 1984, no internet to find custom sizer makers.
We all should know by now, that the harder the alloy the larger it will cast. The opposite is true, also. The softer the alloy, the smaller the casting will be. Now, if you peruse the Lyman Cast Bullet Manual, particularly, the third edition (1980) you will mostly see that Lyman is giving cast data for mainly bullets cast from linotype, which is harder than the majority of us use. They also recommend sizing on the small side. Consequently, there is no need for them to supply molds that drop bullets, much larger than nominal jacketed size bullets. If you happen to stumble on one that casts large enough, go out and buy a lottery ticket.
Most of my revolvers have large throats, right from the factory. I have a early model RH in 44 Magnum. I used RCBS's 240 SWC GC in the Redhawk for 25+ years. Could barely drop a bullet at .430 diameter. I sized to .429 diameter, per RCBS's recommendation, and never any got leading. Treestand accuracy was superb. Worked just fine for deer. Then I got a 1894 Marlin. Fifty yard accuracy was dismal, with cast. It wasn't till I started buying molds from custom makers that I got the accuracy I wanted. However, sizing to .433 diameter was required. No over the counter mold will regularly drop near that size. Tried those sized bullets in the RH's throat and they are a nice slip fit. My CA 2.5" barreled Bulldog is the same way.
An 80's vintage 45 LC Blackhawk likes .454 sized cast. The RCBS mold (250 SWC) won't drop better than .452 diameter. Again, used that bullet for 20 years before I purchased MP's clone of RCBS 300 SAA. Worked OK at treestand distances and no leading but not ideal for longer ranges.
Pythons are known for barrels running .355.............wouldn't know, cause I don't slug barrels. Don't own pin gauges, either. Since the late 70's my only 38/357 bullet was the RCBS 158 SWC GC............358 is the best it will drop. Superb accuracy, with no leading at 20-25 yards. Throats are over sized, will accept a .359 casting but not the .360's, I use for the Rossi carbine...........those get cast from custom makers.
Even a blind squirrel will find an acorn, once in a while. Not going to chance spending $90 (retail) on a two cavity RCBS iron mold, when I can take that money and put it into a custom mold for just a little more............and actually get what I want.
Not saying all RCBS or Lyman molds are undersize, just not my experience. Now if you PC, you can get away with undersize, cause you're adding diameter. I don't, just call me
old school.
