I picked up an inexpensive, used Marlin 1894 made in the late 70's. My goto cast load of a lyman 429244 over 18.3grs of 2400 literally had me spraying bullets all over the target...sideways...at 25 yards. I believe that the bullet drops from the mold at .429
A 5.5gr of W231 under a non-gas checked MP 433640 and it would print a 1.5" round group for 5 shots and drops from the mold at .433 and was sized to .432
Is this typical for the microgroove? I know that the bores are typically oversized, but I did not expect bullets to be sideways at 25 yards!