I don't recall saying anything about slow burning powder, but mid range power such as IMR 4895 which was the army just happen to use in the M1.
I think if any of you are serious about using the garand or any othe military '06 get a copy of Hatcher's Notebook, MG J. Hatcher and see for yourself.
While your at it, read the section on recoil ref: the Bullet or the powder hammering the op rod.
I got my DCM M1 in 81 or 82, and have shot everything imaginable in it (keeping the bullets @ 180 grn or lower).
Having said that, the 180s I used were the older 180 SMKs, the newer 180s are differant. The older ones are more like todays 175 SMKs.
Yes todays powder might be a bit differant, but they do make powder compairson charts.
One year I was running a sniper school (using M1Cs and Ds) we couldnt get ammo so I purchased 5000 rounds of comerical '06 in 165 grn. We had zerro problems. I've use the same ammo in 1919a4 & a6's. Except linking them was a pain in the butt.
I think before one writes me off as being full of poop, you should do a little research. I think you'll find Gen Hatcher is probably the most authoritive on the matter. Remember to check out the Recoil section of his book.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071