Another "Welcome to TFF" from me too! Glad to see another Swede fan!
For starters, what rifle are you loading for?
I don't usually load the 120gr in my 6.5x55s.
I've got a couple boxes of 120s laying on the bench but haven't done any real serious loading/testing with em yet.
I've had better results with 140gr in both my old Gustaf swedes and my CZ550 so I have stuck with that bullet weight.
For 120gr data, I'm using the Speer manual...IMR4350 @ 43.0min to 47.0max.
NOTE: The Speer data is for a modern rifle so drop the max load by 1.0gr if you're loading an old Mauser or Krag!
I'm still putzing around with 44.0grs of IMR4350 (to keep things mild for my old Gustafs).
IMR4064 would be a good powder choice too.
As for the penetration on deer-sized critters...
Try the 140gr. The sectional density and retained energy is much better than the 120gr...and the trajectory isn't that much worse. I have yet failed to stop a deer with the 6.5x55/140gr and I stick with mild loads.
If you've got BIG deer, consider the old-fashioned 160gr round nose. That load is just about "the standard" in Scandinavia as the .270 or .30-06 is over here. The 160gr has been used on Moose and their Red Deer (about the size of an Elk here in the states) successfully for years.
Don't get too concerned with making the Swede a hot-rod flat shooter...
Stick with a heavier bullet, get to know the trajectory of the load you work up, and let that high sectional density number work it's magic.
Remington did chamber their 700 Classic in 6.5x55 in 1994.
The Classics are a one-caliber-per-year limited run. BUT...they must've sold the heck out of the '94 model because I've seen quite a few of em out there.
I haven't been able to find one for sale yet though...a friend of mine has one and I want one too!
They never did offer the caliber as a regular production 700 chambering.
As for other modern rifles in that cartridge...
Ruger offered their M77 in 6.5x55
The CZ550 is still available in the caliber too.
I'm not positive if Winchester or Savage ever chambered that cartridge.