I came into a box of speer 100 gr plinkers . round nose lead sitting in a jacket - wondering about trying them in 30-30 .. any ideas about a powder and will they be stable in older 94's . thought it might be fun to shoot some bunnys ..

Trail boss is your friend

Some great information here.
https://www.marlinowners.com/forum/reloading/31201-lighter-bullets-30-30-a.html

what he said..........or visit Hodgdon's website for both Trailboss

and 60% H4895 reduced load data..........

https://www.hodgdon.com/h4895/

Shoot the Speers to see what happens, only one way to find out, but shoot them in the head.

Back in the mid 60's I loaded the Speer 100 grain half jacket bullet with 10 grains of Unique. I shot a number of jacks with it. Quite decisive. Left an exit wound about the size of a silver dollar. This was using a Model 94 from the mid fifties.

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That is the load that I use with a cast bullet but it works with a half jacket as well.