Jacketed Load Data for Cast Boolits

[Omnivore]

Perusing the Speer Reloading Manual #13 (which I do often. I learn a lot just reading load manuals) I find "Lab Notes" in the 30-40 Krag section on page 288;

Because the maximum pressure of the 30-40 Krag is relatively low, many cast bullet designs cast from strong alloy like linotype can use the same loads shown for jacketed bullets of the same weight. Try the RCBS mould 308-180-SP for general cast bullet shooting.

The industry average pressure for the 30-40 Krag is 40,000 CUP-- just a tad more than that of the 30-30 in which I'm interested at the moment.

Same, exact loads, from start to max, I guess. So; does that mean we can stop fooling around trying to find "cast" boolit loads and go straight ahead with the full data set for jacketed bullets, so long as we're using a "strong alloy"? That one little snippet would say "yes" for cartridges rated at 40,000 CUP or less. One wonders why they tell us this only in the 30-40 Krag section, rather than making a blanket statement somewhere in the front of the book or repeating it in each section for cartridges rated for 40,000 CUP or less. Seems to leave a lot to interpretation-- leaving that little tidbit, in a section for an obscure cartridge, just hanging out there in the wind with no further explanation, no?

No mention of lube, either, which to me, having not done this before, is a mystery, being as, from the talk herein, the lube is a critical component of a cast load. Maybe I'm missing something.

Very odd in any case it seems to me. I find many odd things in load manuals, but others are subjects for different threads.

[btroj]

I have used starting jacketed data for cars loads. But only in some cartridges. Say 45-70 or 30-30 where cast does fine with full power loads. Would not usually do it with something like a 270 win as I don't care to push cast that hard.
As for lube being the critical component, not really. Bullet fit is king, hands down. Get good fit and many lubes will work. Bad fit and it is going to be a long road to happiness. But lube can be a very important part of the equation.
I would have no trouble at all with 170 gr jacketed data for use with my 165 Ranch Dog mould in 30-30. Have used it before, will again in the future. Just don't ever go the other way. No jacketed loaded with cast data. That can get you in trouble.

Good luck.

[MakeMineA10mm]

I have used starting jacketed data for cars loads. But only in some cartridges. Say 45-70 or 30-30 where cast does fine with full power loads. Would not usually do it with something like a 270 win as I don't care to push cast that hard.
As for lube being the critical component, not really. Bullet fit is king, hands down. Get good fit and many lubes will work. Bad fit and it is going to be a long road to happiness. But lube can be a very important part of the equation.
I would have no trouble at all with 170 gr jacketed data for use with my 165 Ranch Dog mould in 30-30. Have used it before, will again in the future. Just don't ever go the other way. No jacketed loaded with cast data. That can get you in trouble.

Good luck.

Outstanding answer.

I'll just add that the reason you can go with jacketed data for cast, but not cast data for jacketed is because cast boolits are always softer than jacketed, so they actually develop less pressures with the same loads GENERALLY (still have to worry about things like seating depth, seating into the lands and other little tidbits that can un-do this principle). And, when loading the other way around, there's not just the fact that jacketed develop higher pressures with the same load. There's also the issue that if you're using a very low pressure/velocity lead load, you can stick a jacketed bullet or just the jacket in the barrel, causing a very dangerous sitaution if you don't discover this.

[Bret4207]

Yes, you CAN use starting jacketed loads for cast of a similar weight. You just have to look at the pressures and what not and use some sense. IOW, you aren't going to use starting 300 Win Mag loads. Some manuals don't start low enough IMO, even for jacketed. The individual gun can make a huge difference too.

Overall I think you're onto the right track.

[marshall623]

I;ve tried it some , it seemed to work better with the faster burning powders that you have data for

[44magLeo]

I have Richards Lee's Modern Reloading. Chapter ten talks about boolit hard ness and how that effects the strength of a cast boolit. Using this strength calculation, you can determine the max pressure the boolit can withstand. He also describes how to calculate pressures for adapting powders for cast bullets.
Using these calculations you can often get more velocity and accuracy than some might expect a cast bullet can deliver.
Intereseting reading. And at about $15 it's not a bad read.