38-55 safe cast size

[Pioneer2]

I have a 336 Marlin re-bore .376 groove 1-16" I sized some .381 /375296 280gr GC I had on hand to .379 and they cycle and chamber fine.Are these usable or should I just buy some .377 cast ?

[Hickok]

If they chamber easy, you are good to go, (as long as you work up a safe load by starting low and working up.)

[Pioneer2]

I'm running the long Starline brass instead of the short Winchester.Too bad as I have a couple hundred of the latter.Powders on hand include IMR 3031,RE#7,Win 748 ,IMR 4198 and SR 4759

[50target]

Friend of mine has a Marlin JES rebore and loves it. IMR 4198 is a good powder to use. Can go from mild to wild. If the round chambers and fires I would think OK. I would start with a mild load and check for pressure signs as I go. Love the 38-55. Found it easy to load for in my Ubertgi HW.
Bob

[northmn]

The JES re-bore might be the SAAMI standard of 2.080 instead of the antique longer chamber. I use Winchester and Starline SAAMI brass in my Marlin and it will shoot as good as I can with open sights. Also, while you can shoot 379 bullets, once shot up yo should look into more appropriately sized bullets.

DEP

[Pioneer2]

So .377 cast instead ?

[T-Bird]

I shoot .378 in my JES rebore 38/55. .377 shot well, but I thought .378 was a tad better.