So I'm convinced that the 6.5-284 is a great, accurate & efficient caliber. I've also concluded that the 6.5 WSM is real tough on barrels for the extra FPS you get. What I haven't seen is info. on the 300 RSUM necked down to 6.5. I presume that most of what applies to the 6.5-300 WSM would apply to a 6.5-300 RSUM but maybe I'm overlooking something. I know that there is a 7.5 % difference in case capacity and that the RSUM would allow the use of a Rem. action. Does a 6.5-300 RSUM exist yet as a wildcat? Any whispers of a factory version? If so, I think I'll wait a bit before I get a 6.5-284 built. ANY input would be greatly appreciated.
For what it's worth, it sounds like you think the WSM cant be built on a remington action. Don't be fooled by the 555 case diameter, the base is still 512 (rebated like a 284) and has the same bolt face as a belted mag. It's a drop in for a long action.
As for "tough on barrels", that depends on who builds the gun and if they know how to throat one. also what type of powder you use and weather or not you think it's a race to see who's bullet arrives first. a 6.5WSM will get you 3300fps from a 140 with 67gr 4831sc. The barrel won't heat up. You'll love it. Throat erosion is a phenomenon caused by a gun builder who can't run a reamer. The blow-by caused by the square or hex shaped hole made with a 5 flute reamer in a 4 or 6 groove barrel is the problem. Also, new reamers are very bad as they are very prone to chatter. You need to hog some material for a while and dull them a bit. A Resharpened, dammaged reamer is a plus also.. It may well be slightly undersize and since reamers always make oversize holes the end result will be a better chamber. I think that many gun builders who have old reamers are fortunate to have them because they actually work better than new ones.
Don't worry about wearing out a barrel. I know of a guy who has a retired 300 weatherby improved that has I think he said 8 full seasons on it and still shoots 5". It's the gun that put him in the PA hall of fame and it's not shot out. My brothers AR15 Match gun with a Stock Colt Hbar has 22000 rounds through it and still shoots 3/8MOA. 20 rounds in 3/4" at 200 Yds out of a 223 Semi Auto. Not bad, eh. Not worn out!
The person who shot the PA 1000yd world record shot it with a gun that he was not going to bring to the range because the barrel was "shot out". Well, he shot 3.151". The reason these shot out barrels work so well is because the throat that has "eroded" is actually just rifling that has "eroded" The bullet now actually sits in a cavity that is the nominal size of the bullet and does not allow the same blowby as the brand new, .002 on a side oversize throat.
Thanks! As usual, there's alot of opinions out there, some based on experience and facts, some based on rumors and lack of experience! That's why I appreciate the input I get here, most of you guys have done the things I ask about and I appreciate your advice. My first hand experience with the topics I post is limited, otherwise I wouldn't ask. As expected, opinions are always a factor, to some, the extra 200 fps is worth all of the potl. negatives and then some, to others, the extra recoil, bbrl. wear, bbrl. length required to make use of the extra powder, etc. just don't make sense. The bottom line is that neither is wrong, and BOTH are right for THEIR needs. I guess if all I was worried about was what I NEEDED, I'd just go buy an off the shelf .270 and go hunting!