You would need a new bolt head. It's the same one for .308, .243, .22-250, etc. Here is the link, assuming your gun is right-handed.

http://www.midwayusa.com/viewproduct...tnumber=461219

Just make sure you get the bolt head for the long action because the long and short action bolt heads are different. You also need to remember the ejector pin, ejector, ejector spring, extractor, extractor detent ball, and extractor spring. That's where they get ya, it's only $20 for the bolt head but $2/piece for all those parts.

As for the feed issue, I'm working on a long action 6.5x55 Swede build right now which is very similar to the .260. From what I've heard, there is no feed issues or any other downsides to using a long action instead of short. The only difference, as you said, is you can have a longer OAL and still fit in the mag.

-James.