Any load suitable for a Marlin should just fine in the Martinis Navy Arms put out. Seems to me, the NA rifles were Octagon to Round in the Martinis, not straight octagonal, but they made both in the Rolling blocks, so probably in the Martinis as well.

Their other Chambering, as noted above, was .444 Marlin. for pressure levels on the .444- look below.

This site is a good one to bookmark.

http://kwk.us/pressures.html

42,000 PSI (Pezio) SAAMI - 44,000CUP (Crusher) SAAMI
51,000 --- (Pezio) CIP --- 45,000 -- (Crusher) CIP