300RUM bolt thrust is far too high for an Encore frame. WSM's are not chambered for same reason. I've had both Contenders and a lot of Encores over the years. Still have Encores for muzzle and my favorite right now is a MGM 24" .357Max barrel. They are unique firearms and you need to acknowledge they are to get the most out of them. They are not bolt guns so you have to work with what they provide and make the best of that.
1- triggers suck. Accuracy will improve dramatically by addressing the trigger. Their lock time is so much slower than a bolt gun so you have to reduce all the variables you can to eliminate target drift as much as possible. I ordered from Bellm a heavier 51# hammer spring (speeds up lock time for hammer rifles by speeding up the drop of hammer) and Heavy Duty firing pin (holds up better to heavier hammer drop) and sear spring assortment. Trigger before sear spring replacement was just about 6 lbs before and was 2 1/2 pounds (which was right on estimate for this spring group) after with RCBS trigger gauge. Directions were outstanding and very easy to follow. Couple of thoughts if anyone is going this route. Use a white towel as the bench mat to keep the small parts from sliding around or taking trip to floor. Made life much easier so you can place parts on towel in order of removal.
2 - forearms need to be isolated from barrel to some extent. Everyone uses O-rings to washers. I cut a 20 ga hull, punch a hole and it fits to barrel profile and still isolates the forearm a little.
3- replaced standard forearm screws with hex head versions and allows to torque to a spec easier.
4- high recoil calibers such as a 300WM may cause the action to open if it is a reload that is maxed out. Simple fix is to replace the barrel recoil lug spring with their 12ga recoil lug spring. It held on 500SW barrel that did open with heavy reloads with no problem. An easy way to remove is using a ratchet clamp wood vise, just clamp behind the pivot hole and the lug, squeeze it down until you can punch out the pin. Replace spring in reverse order.
5 - it is a 7lb rifle so any heavy caliber will kick your *** no different then a bolt gun. Muzzle breaks do work nicely on them.
6- when shooting off a bag, it is unbelievably critical to find the sweet spot under the forearm to rest the barrel each and every time. They are one of the most sensitive rifles I have ever shot for this concern. Once you have the sweet spot they are capable of really good accuracy.
7 - my .357Max will hold MOA out to 200 yds with 190 gr. Fury bullet so it can deliver reasonable accuracy.
8 - I have been thinking of a poor man's LR with it using the .300WM and ordering a barrel from MGM with 1:8 twist, muzzlebrake to shoot the heavier bullets. Or a .270 with same thoughts on twist.
Don't underestimate their accuracy capability, they can be quire good.