This optic was installed on a S&W 500 with a 8 3/8" barrel. I purchased a special Weaver style rail from Weigand which is machined from stainless steel and made specifically for this revolver. I bore sighted it myself for the tip of the delta at 25 yards & my first shot was 4" high & 2" to the left while really taking my time & relaxing while resting the gun on a bipod. I reset the windage & elevation as per directions and my next shot was 1" high. After taking 6 more shots I stayed very close to the impact point I was aiming at but it got worse towards the end. This gun now weighs close to 70 oz. with the rail & sight & the more you shoot it repeadedly, the more strain on your hands, arms & legs occurs. After taking a 1/2 hr. break I was back on target. Next I will go to the range & see what happens at 50 & 100 yards. I am presently shooting Hornady 300 grain which might be a bit small at 100 yards but the guys at S&W tell me I might need to go to a 500 - 600 grain. for that long of a shot if I can stay on target. Believe me, this gun is awesome, but heavy. The compensated barrel helps but it is still an animal. The sight stayed on target until my arms got tired.
This review was written in the old system and had content requirements that are different than reviews written today.