so I loaded it up with 60gr powder and it shot very well! ...., so would this be enough to penetrate deer at 50-70yrds?
Short answer... a 60 grain load of 3Fg launching a .530 PRB, I would expect to
go through a deer shot broadside through the ribs at 70 yards or less, with a barrel 28" or longer.
I shoot 70 grains of 3Fg and a patched .530 round ball. I started with this load with a rifle that is 1:48 because in my state, 60 grains is the minimum legal load for deer with a muzzleloading rifle. To "play it safe" I started with 70, and it was super accurate with that load.
When I got my current rifle, which is a 1:56 twist. It shot very well with the old load, and did fine with an 80 and 90 grain load, but I went back to the 70 grain as I didn't see any advantage. When on one hunt, I shot a very large doe, and the ball went through and through at 110 yards (I normally shoot closer), I confirmed that 70 grains was plenty for me out to 100+ yards. So 60 grains should be fine for you out to 70 yards.
NEVER sacrifice accuracy for 10 grains of powder. Placing a shot on a deer is not the same as placing it on a paper bullseye at the rifle range. Deer can move slightly as you squeeze the trigger, the weather and the sunlight mess with your sighting. So you can try higher powder loads. Some will tell you 90 grains... which is 50% more than you use now. Will you gain any advantage? Who knows? Some folks increase the load until they see "significant" changes in target grouping. (imho) If the groups on your target open even slightly, I'd go back to what shoots the straightest. If you increase and see tighter groups, then go with that.
Dead is dead. Once the bullet exits, if it exits with just enough velocity to get through the hide on the other side and falls to the ground, or exits with enough velocity to kill a second deer standing behind the first... means nothing to the first deer hit.
LD