I bought the same gun a few years back, Remington Light Varmint Stainless Fluted in 221 Fireball. Very inconsistent POI. I'd get little groups but they were all over the place on the target. I discovered the synthetic stock was giving random points of contact on the barrel. I folded a business card and stuffed it under the front of the forestock and got the same POI.
Swaped out the POS synthetic stock with a Boyd's Thumbhole Laminate. Wow, what a difference. Now it shoots little bug hole groups. Far and away my favorite load for this gun is the Nosler 40 grain Ballistic Tip using Reloader #7 powder and Federal primers.
I also reform my own brass from 223 military brass. This link will show my process. It looks somewhat tedius but it's not that bad.
I finally got around to it - 223 to 221 Fireball (pic heavy) - Shooters Forum
I've spent quite a bit of time with this gun and sent lots of bullets down the barrel. It's a fun gun to shoot and you get many, many, many reloads from the brass. This is it.