I have put a 300 gr barnes XTP thru a moose and shot several deer with 250 gr projectiles that would weigh 250-300lbs using less powder then you are. Since your wanting to aim at the scapula I'd suggest a nosler partition or barnes saboted bullet, but bare in mind approaching 300 yards your at the short end of the stick with a ML. So if this is the ranges I'd stick to putting the bullet through as little media as possible aka behind the shoulder. If 200 or under then fire away at the shoulder if you want.

The longest I have shot at a deer with an inline shooting subs was 227 yards, 110gr loose t7 and 250 gr hornady sst passed through the ribs and lungs = dead deer! The wound channel was rather unimpressive basically a 45 cal hole straight on thru. Your dealing with a projectile that has a very poor BC and sheds its velocity and energy quickly, penetration or lack there of will ensue as you get further out.