[Pioneer2]

I believe the .444 has a 1-38 twist as opposed to a 1-20 that would have been more versatile like some .44 magnums.One way to find out if H-335 is the powder for the 300 grainers.From the 2nd Edition LEE manual 300gr jacketed OAL 2.620" .H335 starting load 49gr/1935fps......MAX 52gr/2023fps compressed load.
IMR 4895 starting load 46.6gr/1762fps......MAX 50.6gr/1915fps compressed load
IMR4198 starting load 36.8gr/1796fps.....MAX 39.2gr/1911 fps
From Ken Waters Pet Loads the most accurate load for the 265gr was H-335 @ 56gr /1947fps........ Best 240gr load with IMR 4198 was 49.5gr @ 2400fps