I use IMR 4350 in my 3 6,5x55 rifles,all are 21 in or shorter, with a 140 gr Hornady sp interlok . At 2600fps or so when I hear my wife shoots I just go pick up her deer. The Nosler 120 also have a good reputation in the 6.5 rifles. The rifles all shoot the Hornady under an inch with the original barrels and my load but I am not pushing them hard.
If you fall out of love with your original 6.5 Encore barrel I know where it can find a good home in KY.