They are all "magnum" barrels - i.e. capable of holding 150grn of powder. That being said, almost nobody uses that much of a charge. Accuracy goes to hell when you do. Most find that a charge of 100grn +- of 777 gives plenty of velocity and good accuracy.
As to scope mounts, all Encore rifle barrels have the same hole pattern for bases.
If you want better answers, I recommend you go over to WWW.EncoreClassifieds.com
and lurk on their forum. Lots of good Encore information there.