Re: Sako M995
Yes and no. Both share the same footprint but TRG-S (M995) is an open bridge receiver with a Sako wedge type dovetail, while TRG has the straight 17mm "Tikka dovetail" and as I'm sure you know it's the closed brige design. The biggest problem with M995 is a combination of several things; Being a large action for 338LM sized cartridges, the front and rear bridges are far apart. The top having a large cutout combined with the fact that the scope base is the Sako's proprietary wedge design means you need Sako-specific, extended rings. I would definitely recommend installing a one-piece picatinny base.
Triggers and stocks are interchangeable within certain constraints. For example, the original trigger with the top safety will not fit the TRG chassis without modifications but as far as the receivers go, the triggers swap out just fine. Likewise with magazines, they have an identical interface to the receiver, but one will not work in the other's stock/chassis.
I've had this M995/TRG hybrid for a couple of years now and it's my go-to gun. Started life as a 30-06 but is now sporting a 6.5 swede barrel. Chassis is TRG-41/42, trigger and magazine are TRG-42, and the stock is TRG-41. Just goes to show you can mix and match if you know what you're doing...
(14lbs)
Looking at magazines from the front. M995 original on the left, TRG on the right. The release notch is on opposite sides in the original M995 stock vs the TRG chassis (well, the trigger group, actually).
Underneath the pretty clothing of the TRG trigger group, the triggers are essentially identical.