Years ago I used to shoot a lot of 20 ga. Winchester AA compression formed hulls reloaded to factory specs but I was shooting them out of a Winchester 101 with 2 3/4' chambers. I don't know what the specs were from then but I know they were over 8,000 psi and probably closer to 10,000.
I still have some of those reloads but I will not shoot them in my L.C.'s only in the Winchester. Great shell, I could get 13 reloads out of them before the mouth cracked.
I think that if your chambers are 2 3/4" the 1150 fps is ok. I don't know how much more pressure would be at a 2 1/2" chamber but I wouldn't chance it.