I purchased an Encore with a 22 250 barrel soon after they were introduced. I have to full length the cases to close the action and I start to get head seperations after 3 or 4 loadings, is this common? I sat the gun up and have not fired it for 3 or 4 years. I would like to use this gun but not with this result.

I suspect that your sizing die was not adjusted properly or, more likely, that your loads are too hot. Size the cases enough so the action just closes easily and no more. Furthermore, I haven't had a problem with just neck sizing (usually with a Lee Collet Die) for my Encores and Contender.

I have loaded for a BUNCH of different Encore and Contender cartriges and have never had the problem you describe including with my 22-250 barrel. If your problem persists, there is probably somethng wrong with the gun. In my experience, Thompson/Center has given excellent customer service; if there is a problem, I'm sure they'll fix it.

Headspace and proper set-up of one's reloading dies are key issues with any firearm but especially so in the single shots. Addressing such would take a while, so I will recommend the following link:

www.bellmtcs.com

You'll find plenty of good information there.