Re: 5.7x28
pacific tool and gauge has made rem 700 bolt with the proper bolt face. i have shot one of those and they are fun.
also check out a rem rim fire conversion from the 540 580 or 590 series. the bolt is two pieces so a new front half can be made. check out the conversions.
match grade machine also makes encore rifle and pistol barrels. i have a 12 in pistol and it is fast and accurate.