Marlin Cowboy 38-55 twist rate??

[Dom]

I have been shooting a 250gr & a 260gr cast bullet in my Marlin Cowboy 38-55, quite accurately. I thought this was the heaviest bullet I could shoot in it . Now I realize it has a 1/18 twist rate. Should this be able to stabilize a 300gr bullet?

[PositiveCaster]

Some have obtained good accuracy with 300s in a 1:18” twist barrel - but I don’t know the velocity they used. The slower you go the less stable the bullet will be. You’ll have to try it.



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[warren5421]

My brother's Marlin won't cycle 300 gr unless you set way deep.

[Dom]

Well it appears I answered my own question. Found a .380gr 390gr mold. Bullet length of 1.07. At 1400fps. 1/18 twist. Stability rating of 2.30. A winner for my Marlin 38-55. https://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi