I would advise against a .270 in an Encore pistol. A .270 is an "overbore" cartridge. Without getting into a ballistics lesson here, just suffice it to say that any overbore cartridge becomes "inefficient" in a short barrel. There are lots of good calibers that work well in an encore pistol though. The previously mentioned 7mm-08 is a very efficient cartridge in a short barrel. There are others as well.
If you really want to get serious about this, go over to the Specialy Pistols forum. There are lots of true experts on there who can steer you the right direction.
http://specialtypistols.infopop.cc/eve/forums