Now a 6.5WSSM sounds VERY interesting to me, but im guessing its sort of a specialized build. Or at least how i would conceive it (even when very well implemented) might just turn out to not be what one wants.
My 6.5 WSSM was built on a Browning ABolt II that was originally a .223 WSSM. The barrel is a 19" SS Shilen with a light sporter contour. Last spring, I had just started working loads for it when my wife decided it was time to down-size.
The project was intended to provide 6.5x55 power and range in a short, quick handling package. I thought I would like the tacky rubber covered synthetic stock, but it has yet to grow on me.
This project has taught me a couple things about the WSSM's:
1) If you base your 6.5 WSSM on a .243 case, by all means use that case. It will make life easier for you. (Mine is a 6.5-243 WSSM.)
2) Necking up the .25 WSSM is easier than necking up the .243 WSSM, but the shoulder angle is different enough and Winchester brass is heavy enough and stiff enough that fire forming and blowing the shoulder out to the 243's shape is nearly impossible.
3) Hornady's .243 WSSM brass is excellent brass! I was pleasantly surprised to find it much better quality than the 300 rounds+ of Winchester brass I had on hand.
4) Lighter bullets are going to be better as the rounds have to be no longer than the SAAMI spec if you intend on the rifle being anything more than a single shot. Anything longer, probably will not feed through a WSSM magazine in a WSSM receiver. Believe me.
5) Sierra Game Kings and Pro Hunter bullets seated to SAAMI spec feed just like they should. Any bullet more pointed than the Pro Hunters tend to hang up / bind before entering the chamber before they can clear the magazine. Including Hornady Spire Points. And I will never get a Berger bullet to cycle from the magazine. No way, no how.
IF I ever get my shop set up again, and that seems to be getting to be a pretty big "IF", I'm thinking I may see what I can do for a different stock. Maybe buy a blank and whittle it into a nice shape and make it a single shot with a follower and no magazine. Or maybe convert it into a blind magazine without a floor plate? I dunno. Just fantasizing, I guess.