TRG has some good advice but I have to say that before you buy a Rainier, take a look at the reaming of the chamber in the extension. My Ultramatch barrel as well as its replacement both look like they were reamed with a Dremel and required polishing before rounds would extract reliably. The barrel has not been a great bench performer (went though load development with 5 powders and 5 bullets at ~1.5 MOA best average group) but is more than adequate for run-and-gun which is how I primarily use it.
See a picture of the chamber below. The original barrel as well as the warranty replacement were of similar quality. Fired brass had visible striations (fine lines) around the circumference.