Your loads of 250 grs at 1000 fps will be fine, I shoot 270 gr Thunderhead bullets in my 45 Colt SAA revolver at 940 fps, and have been for years without a problem to the revolver.
Henry also makes a 44 Magnum lever action rifle, and I am most certain those loads are much higher pressure than the load you mentioned, I'd get that rifle zeroed with the above mentioned load and be practicing for deer this coming fall 2013.
Gunner
