While rifle manufacturers put maximum load recommendations on their rifles, so do powder makers. I would guess that you have exceeded the "considered safe" load for that rifle with that powder. I would suggest you reconsider your actions and lower that. For the sake of the rifle, yourself, and your wallet.
Whether it is safe or not... I'm no engineer and could not tell you one way or another. Are you gaining anything really?? ... that is the question. If your shots are all 250 yards, you might have a slight edge. And I do mean slight. But would say 120 grains of the powder give you the same results or better? Probably.
You have already discovered that your accuracy group size could improve. I think that will happen if you drop the load down to the 110 grain range. Will this effect the killing power of the load. Not by anything you, I or the animal you shoot would noticed. Even with 110 grains your going to get about the same penetration and wound channel.
These gun companies & powder makers are selling a dream to the American public. Purchase our new fancy redesigned MAGNUM rifle. Have the best out there. Well its a dream. I have old hammer striker models that will shoot day in and out with the new top of the line guns. But then that does not sell new guns to tell the general public that kind of thing.
Same with powders. We all want a better powder. This powder you don't have to swab. This powder cleans with water. This powder does not clean with water... etc. I was shooting nasty of Black Powder the other day. The second patch out of the water bath was clean. The water was free, the patch was an old T shirt, and the rifle shot fantastic with 85 grains of powder and the projectile. Would that rifle hunt... others believe it would. Could I shoot 250 yards with that load? Probably, but I never would. That is not the way I hunt. And if you do, more power to you. I back you 100%. Just not for me.
So do yourself and your rifle a favor. Drop the powder charge and see what happens. At least contact Thompson Center and Blackhorn 209 and see what their opinion is on the load your shooting. Play it safe if what I am getting at. Enjoy yourself.