JM Marlin Cowboy .38-55

[warren5421]

Anyone know what the barrel on a .38-55 mic's. Don't have the gun here but need to load some ammo for a Cowboy .38-55 made around 2003. The gun has only had 100 rounds of Blackhills .38-55 through it. No help from the guy that shot it as he had no idea. I know the gun may have a different bore diameter but I need a place to start. Do I start with .380 or .375 dia bullets 240 gr RNFP in weight.

[Eddie Southgate]

Do a search here. I think .377 will be about average . I got an '85 Winchester that like it's cast bullets at .379-80 but Marlins will likely be somewhat different .

https://www.marlinowners.com/forums/

[1006]

I think the Black Hills 38-55 is .377 and loaded to about 1200-1300 fps, but most guys seem to like the .379 in the Marlin when I read about it.

I have Winchester 375, and my knowledge regarding the Marlin is based on what I have learned while picking bullets for my 375 Winchester-no first hand experience.

[Mk42gunner]

Mine (a Marlin Model 336CB) from 2001 slugs closer to .379" than it does .375". I am currently using a .379" H&I die and it seems large enough with a limited amount of shooting.

Never tried any 240's, all of mine are at least 250 grain. I am starting with the Lee mold (no gas check).

Robert

[rockrat]

Mine came out at around .379" too

[Texas by God]

Load a dummy round of each diameter bullet and let him see if they both chamber ok. I won't load ammo at all if the gun is not present.

Sent from my SM-A716U using Tapatalk

[1Papalote]

I'm shooting as cast Lee 250 at .381 and short brass. COWW+2%. IIRC mine was .379?

[earlmck]

Mine is a full .380 and I'm sizing .381.

[wdr2]

My 3855CB is also 0.380, I size to 0.381 using Starline brass.

[richhodg66]

My .38-55 has an after market barrel, but it likes them the fatter the better. .379 seems to be about minimum that works well, I cast the Lee bullet )good design, by the way).

If you don't already have dies, spend the extra money on the RCBS Cowboy Dies if you plan to load cast. Made a world of difference in mine.

[Mk42gunner]

To expand on the brass issue, basically modern Winchester brass is too short for the chamber but Starline makes both lengths. There is an article explaining it on Starline's website.

Earlier this year, when I discovered a few mice had been using my new box of WW brass as a urinal, I ordered from Starline. They were out of the less expensive short brass, but had the longer in stock, so that is what I got.

The RCBS Cowboy dies work great.

Robert

[brstevns]

Mine came out .3755, while my cousins is .378 I size .378 for both of us and they are working well. A win I have mic's .380

[farmbif]

I've found its best to measure what you got rather than loading up a bunch of shell on just a guess. but maybe that's just me.

[beltfed]

My 336 CB is a tack driver with 0.379 " bullets 375449, NOE 235 RD and 375248
NO trouble chambering.
Talking 1.5" at 100yds. Deer Loads of Re7
beltfed/arnie

[saguaro]

I shoot .380-381 cast in mine.

[richhodg66]

I've found its best to measure what you got rather than loading up a bunch of shell on just a guess. but maybe that's just me.

Maybe it's because my reloading bench is a 30 second walk from my shooting bench, but I never slug bores or other things like that. It's been my general experience that the biggest diameter that chambers and extracts easily a loaded round will work the best anyway, so I'm usually a "try it and see" kind of guy.

Especially for .38-55 with soft lead and low pressures, I'd load them as big as I could.

[richhodg66]

I shoot .380-381 cast in mine.

My experience strongly holds with this.

[hornady308]

My cowboy is also on the small side. I usually size to .379 for 38-55 rifles, but the cowboy demands .377 (so I had to buy another H&I die, of course).

[Rrusse111]

.379 and the long starline brass, Lee dies.

[ELFEGO BACA]

I started with starline’s long brass and size to .381.
Seems to work ok!