I sighted my ultra in at 50 yds. with Remington Premier Copper Solids. It is a 20 ga also. Shoots 1" groups at 50 yds. and 3" groups, 3" low at 100 yds.
I emailed Remington to get ballistics for further shots with this load because is shoots so well from my gun and the box only shows balistics out to 100 yds. The energy at 100 yds. is 986 lbs., which is getting a lil slim. The response from Remington was that they do not recommend shots past 100 yds. On the web site though, they give balistics for it at 125 yds. as being about 7" low.
My guess though is like all "legally savy" businesses, the round is probabily fine at 125 yds. - provided it is a good placement. They just like to cover their buts with the closer recommendation. Helps avoid hate mails when a bad shooter misses a deer at 125 yds.
Hope this helps!