I have two of them that I built, one on a rechambered Savage and another in an AR-15. Both rifles see approximately 300 fps increase in speed over the standard cartridge, and the brass doesn't stretch much. Beyond that there's not a lot of difference. My reamer is set up for a tight neck, but in both of these rifles I went back and opened up the necks to standard size so I could fire factory .223 ammo in them to form the cases. I use a Lee .223 AI die to seat bullets and a regular Lee .223 collet die to size the brass. Accuracy is fantastic, especially in the AR-15, but so is a regular .223 if it's built right. Is it worth it? Sure, if you're going to rebarrel anyway. Lee dies are cheap, you get close to 22-250 performance with 10gr. less powder, and the brass looks cool. Just make sure whoever barrels your rifle knows how to set up an Ackley cartridge and headspaces it correctly. The bolt should close with a fair amount of resistance on a factory case, and if you fire a primer in an empty case it shouldn't be sticking out at all when you extract it. If it is, you have too much headspace. Not all gunsmiths understand this, make sure yours does.
