"...both MN and No.4 MK1? Have any of you tried their 174 .312 Round Nose and .312 150 grain SP in your MN? I'd like to have one bullet that I could load in my MN''s and Enfield. It would save me some bucks. "
Yes I just tried the 0.312dia, 174gr RN Hornady's in my MN 44 carbine. With iron sights from the bench it was putting out consistent sub 3" groups at 100yds. (4 groups, 3 shots each) on 54gr of IMR-4350 and Privi Partesian cases. Cases have been fired several times and still look great. Pressure is good could probably bump load up another grain or two. 3" at 100 is at my limit for iron sights, rifle can probably do better. Groups are centered left to right and ~1" high in elevation. Not bad for an old war horse.
Liked the new ammo so much, went and got a fullsize MN, but haven't fired yet.
Will have to go looking for the spire points. Need more reloadable brass.