Re: barrel cutting ?
I wouldn't worry about performance. You'll lose a little FPS but it won't be a game changer. Handloads might need a little tweaking.
I have a 26" SPS Varmint that I'll be chopping to at least 20, possibly to 18.5" and threaded. Most folks that have chopped this barrel from 26 to 20" only lost 70 FPS. I'm chopping this short for convenience and for the additional length of a suppressor. I don't want to have 35" of tube out in front of me with the suppressor.