I've owned several Marlin 1894 44mags over the years and recently bought another. Except for my 1894 Octagon made in 1973, all shot somewhat inconsistently, including the latest, a standard 20" round barrel pre-safety model.
I can completely forget cast bullets (MicroGroove barrel), they're all over the place, and jacketed semi-wadcutters don't print well either. Round nose 240gn jacketed hollow or solid points seem to do the best. I mostly load moderate heavy to heavy with 2400 and BlueDot.
Anyone have similar experience? Maybe I should try heavier bullets with more bearing surface?

I load Hornady XTP's with 2400 for mine. I usually use the 240 grainers, but tried the 300's last fall on a whim and had a 10 shot group of 1" at 100 yards.

Mine works well with the Speer 240 grain and the Hornday 200 grain XTP and stiff loads of H110/W296. I have better luck than you with cast but not SWC or Keith. WFN or RN and a bullet diameter of .430" or more and generally medium level blue dot loads. Yours being an older one it may like the lighter bullets better. My Smith 29 from that era does best with the 180 and 200 grain loads more in fashion during the 70's.

its not a marlin but....my load for my rossi92 levergun 44 mag is Hornady 240 gr. XTP in front of 16.8 gr. herc 2400 with average vel of 1472

Try some Speer 270 Gold Dot Soft Point factory loads. They shoot good in my Winchester 44 Trapper, and my S&W Mod 29,s.
If they shoot good then you can reload some with H-110.

As to cast bullets, have you tried some 'hard' cast bullets and slowing them down? You'll probably see some improvements. Soft lead and high speed are not a good combo no matter what the rifling.

I've tried cast pills on pigs from my 96/44 Ruger and it was like using 30 cal FMJ's - no stopping power at all unless you hit a large bone. They were RNFP cowby types.

Nosler non-partitions 200 and 240 gr. have given good accuracy for me; the 250 partition not quite as good; 200 speer SP have had good accuracy; the 210 GOld Dots have not.

THis in old Ruger .44 carbine and H110; will work up loads for Trapper carbine this winter.

Some good info on here:


http://www.reloadersnest.com/

Both of these work well in my Trapper. Please work up to these loads.
Hornady 240gr xtp
WW 296 23.5gr
Rem nkl cases
CCI mag primer

Hornady 265gr sp
WW 296 22.0gr
Rem nkl cases
CCI mag primer

The 240gr will stay in 1" at 50yds, with the 265gr going about 2" and they hit like a hammer. Sorry I have no chrony data.