I have been experimenting with a couple lever action .44 magnum carbines, a Rossi M92 trapper and a Marlin '95 ( ballard rifling) stainless. The Rossi trapper is a self defence rifle, the Marlin meant for general use. The marlins slow twist & large bore is frustrating.
After a few trials and tests, i have the Rossi shooting OK with the NOE 265gr. RFP bullet at about 1100 fps, but the Marlin even after trying several lighter bullet styles and diameters continues to mock me.
Both rifles shoot jacketed factory loaded bullets OK, but the Marlin seems to want them exclusively. I slugged the bores, and the Rossi is .430 diameter and .431-.432 diameter cast bullets shoot good.
The Marlin is .4325 diameter, and the largest size die I could find is .433. I was getting bullets hitting sideways at 100 yards with a mild load of 7 gr. unique under a plain based bullet and 1100 fps. I did not try gas checked bullets in either rifle. Should I try heavier / faster loads, and try gas checks, would that help? Or just give up on the Marlin. I might just trade it off on something more cast bullet friendly. What do you think?

take a look at Dardas boolits........up to .433" for 44 cal's

.432" should work good for the Marlin

http://www.dardascastbullets.com/mm...ode=44200RNFPBB1000&Category_Code=44

You really need to use a wider diameter cast bullet. Marlins have a reputation for having large groove diameter barrels. One Marlin rifle in 45LC that I know of didn't shoot well with cast bullets until the owner used 458 diameter cast bullets.

NOE list 434 diameter moulds or you could design your own mould using the Mountain Molds program. Specialist suppliers like Buffalo Arms and Tracks of the Wolf have a range of oddball sizing dies. I have had a few sizer dies made by "Buckshot" on the Castboolits site. He will make any non standard size - his work is excellent and his prices are very reasonable.

I once had a Marlin '95. in .44 mag. I did not know of the over sized bore problem at the time. Mine was doing well if it shot a 4in. group at 25yds. from a bench. I don't remember it shooting better/worse with cast/jacketed bullets.
I sure liked the way that little carbine handled. But, guns that don't shoot accurately don't stay here long.
His little brother in .357 mag. would consistently shoot 1.5 or less at 100yds. with an aperture rear and factory front sights. It moved on to make room for groceries. I sure would like to have that one back.

try heavier and slower. also the 434's should help. marlin 44's are notorious for being fussy about diameter. also try some trailboss if you can find some. i had 2 1894 marlins made the same year. one loved jacketed and the other wanted cast. i also recrowned both after getting them to both work with either style bullets and with the recrown, both shot groups around 1.75" at 80 yards. traded one off but will have a hard time letting go of the keeper.
don't despair you can get yours to shoot well.

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The Marlin micro-groove barrel was button rifled which causes it to be a bit oversized. Heavy weight bullets do not shoot well in the 1:38 twist barrel, which likes the 240 grain bullets in my rifles. My rifles shoot cast .434 best so I had to buy a custom mold. Gas checks are of no value except on full power loads to reduce leading.

Ive got a 444 model 94 that does well with cast, I was told it had a faster twist than others.