If you are ever in the Austin area Blackjack has very good reviews and has done this for me with excellent results as well as many other gun related repairs/improvements.
Dale Wise Custom Guns
1402 Blanco Rd, San Antonio, TX 78212 Reviews
Some years ago about 1992 I had a Ruger bolt action rifle chambered in 7.62x39 that was just a so so shooter. I decided I wanted a 308x1.5 Barnes and since the bore was .308 instead of .311 I decided to have the rifle re-chambered. They had to open up the bolt face for the 308 case head then re-chamber and headspace the barrel. They even managed to make the dies for me from a set of 308 Win dies.
It would shoot a 150gr bullet at about 2500/fps and group under an inch all day. It was the perfect hunting rifle for me for deer under 200yrds. Didn't ruin as much meat as a .243 or 308 Win. One day I was at the range and the guy next to me asked to try it and ended up offering me twice what I had in it. I was short on cash at the time and accepted his offer.