I have shot the 300 WSM comptetitively for 6 yrs now. I have two and building another. I also hunt with the 300 WSM.
It is a top notch 1k BR caliber for sure. We cannot explain it but, the 300 WSM is having uncommon barrel life compared to the other mags and particularily compared to the 7mm WSM.
My first barrel went 2300 rds and took 9th at the Nationals. I have a friend with 4000 rds thru his 300 WSM and still winning with it. He just posted that the throat has only moved .020 since starting. Now he has been shooter of the year several times also so he is top 2% in comp and extremely knowledgable.
Either 1-10 or 1-11 twists will work. you want a min SAAMI reamer and .338 or .340 neck with the .340 might being no neck turn., but no need to go below .338 IMO. I would recommend going to Pacific Tool and Guage and talking with Dan Kiff and getting him to get your reamer and go guages (under $200). As for smiths, go to a top 1k smith (look at the "top Recommended smiths" url at www.6mmbr.com
As for bullets, 210 Berger or 210 JLK and maybe 200 SMK Sierra, H4350 or MRP powder, Norma Cases and F210 primers.
If you are in NY area would recommend a PA taper barrel, Harrels brake and make weight at 16.5 lbs with NF scope. That way you can shoot PA, IBS, NBRSA or FClass with same gun. Bruce Baer has a modified Edge (extended in front) with MBR rear with 1/2 flat on bottom that is super for 1k. Mark King, Bruce Baer and Eric Springman in PA are all top 1k smiths and LR hunters. John Myer in VA is another.
Go to the PA and IBS websites. The 300 WSM is a top comp caliber.