300H&H,
A Dakota would be a real no-go in an Encore. The WSM's are really pushing it and if you load it to bolt levels you will not be pleased. Most companys won't even chamber a Encore for the WSM's even. Some will chamber the Encore the larger caliber RUM's-again this is the minority.
There is probably a good reason why Thompson does not chamber a head size over the standard 7RM case. Even with the standard magnum size head in a Encore you can flex teh action to the point where the frame will pop open on you and your brass will experience case/head seperation. I have been there and done that with a 338WM a number of years ago. You can have good accuracy and case life with any of the standard magnums, but again you cannot load them to the levels you would in a bolt rig. With that in mind, I typically consider the 06 case improved as my preference.
Kirby has had some experience in this area as well with the Encore and I hope he chimes in.
The SP site is the most active one I know of for specialty handguns. Steve, Marc, and I even moderate the LR handguning section.
Most of the guys at SP are not going to be shooting the heavy high BC bullets for LR.
On my old 16" 7.82 Patriot XP (Short action 30 caliber lazzeroni case) I pushed a 180 grain SGK @ 2775 fps from the muzzle. The 300 Winnie in the Encore couldn't touch it velocity wise.
You can basically take the magnum rifle data and subtract 300 fps and that is about what you wil get in a SP chambered with the same set-up.
There is my 2 cents worth /ubbthreads/images/graemlins/grin.gif