I have not played with my 260 Barrel much so far. I am sure yours with enough glass will really reach out. I had a free 20X Super Sniper Rifle Scope laying around a couple years ago. I installed it just to see what the Bullberry 260 barrel would do. I was using computer generated drop chart data. I was shooting at 100 and 200 yards to get a Zero on the scope. I do not remember if I went out any further before I dialed it on up. I put Four of Five shots on a 10 Inch Steel Plate at 600 yards the first time I fired at that distance. I put all Four hits on the top edge of the target, so it was shooting a hair flatter than my drop chart data suggested.
I have it set up for hunting now with a 2.5 - 10 Weaver Classic Extreme 30mm Rifle Scope. This was my first muzzle braked handgun barrel that I was impressed with. It has Bullberrys radial muzzle brake.
Have you worked with your 260 any more the last week or so?

Bob R