Jacketed Bullets Loads for Cast Bullets

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Standard Member

JRSR posted this 05 September 2024

I'm working on cast bullet loads for 300 Blackout. My Lyman book only has 4 loads for a 160 grain cast bullet. They have lots of loads for 160 grain jacketed bullets as does my Lee reloading book. Is there a formula or standard to make a jacketed bullet load work for a cast bullet of the same weight? Thanks for the help.

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CBA Member

fc60 posted this 05 September 2024

Greetings,

Here, a chronograph is your friend.

Start with the beginning charge weight for the jacketed bullet substituting your Lead bullet.

Chronograph the result and compare the velocity to the loading book.

Lead bullets seal the bore better than Jacketed thus requiring a lesser amount of powder to get the same velocity.

Just do not exceed the maximum velocity (i.e. pressure) listed in the published data.

Another caveat is seating depth. If you seat the bullet deeper, the pressure rises.

Here, again, use caution.

Cheers,

Dave

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JRSR posted this 05 September 2024

That makes perfect sense. Thank you very much!

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Wilderness posted this 05 September 2024

My experience with .30-30 has been that cast bullets of the same weight may give 100+ fps more velocity than jacketed with the same powder charge.

By way of illustration, Lyman #46 has .30-30 loads for 170 jacketed and for #311041. From that data it is clear that the extra velocity from cast is not a free ride - it is achieved by extra pressure. Example: 35 gns 748 with 170 gn Hornady gets 2116 fps at 30,100 CUP, but with 170 gn #311041 it is 2270 fps and 32,900 CUP.

Cast bullet design can have an effect also. My 175 gn .30-30s (sized down #U321297HP - longer bearing surface) get 2190 fps at 12.5 feet with 32 gns LVR. Larry Gibson's load (Cast Boolits post) for similar weight #311041HP was 34.5 gns LVR for 2218 fps at muzzle. Both with 24" barrels.

Bottom line - use your chronograph to work up towards the velocity you want.

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JRSR posted this 05 September 2024

I'll need a chronograph now!! Great excuse to buy one.

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Coydog posted this 08 September 2024

I have read that you take the load data and reduce it by 10% of the starting load from Jacket to work in cast . Has anyone else know anything about that ?