I find in mine it shoots both the long and short conical fine. I think the longer conical being the 435 grain Maxi Hunter would stabalize better and be more accurate at the longer range. The best way to find out is to try them.

Yes your trajectory will suffer with less powder and a heavy bullet. All you need do is adjust. As for blowing a big hole through the deer, that should not be the worry too much. Granted if they hit bone they will start to flatten out but not like a sabot. They plow their way through most of the time and leave at least a 9/16th size hole through the animal. If you put a hole that big through them, in a vital spot, the animal will go down sooner or later.

I have not shot a deer yet with my new 380 grain conicals. I just started making them. The 300 grain put them right on the ground, but then the first deer was a spine shot out of a tree, the second a neck shot at the base of the skull, etc. I have always put them in a hot spot and let the size of the bullet do the rest.

80 grains of powder is plenty of punch out to 100 yards and further. Shooting 80 grains I put a round ball through one deer at approximately 75-80 yards with enough force that it killed a second deer behind it. So have fun, and work up your load. You have a great shooting rifle there.