I use GOOD 140 grain bullets for everything, other than Coyotes.
I use Lapua brass, CCI 250 magnum primers over 51.0 grains of IMR7828sc.
Velocity is just over 2800fps, and if I do my part, 1/2 moa is a consistent grouping at 100 yds.
There are others on this site, that use the same load in their T3 rifles as well and they all report similar results.
T3s are quite forgiving of everything, except neglect.
Other powders that worked well, with the same bullet weight, cases and primers were
54.0 grains of RL25, which gave slightly faster velocities but the accuracy opened up to over an inch.
49.0 grains of RL22 which gave appx the same velocity but accuracy was again, over an inch
53.5 grains of H1000 which gave appx the same velocity but accuracy was inconsistent and the load had to be compressed more than I like to.
H1000 works best when it's compressed, IMHO.
These loads won't be found in any manuals and are DANGEROUS IN Swede milsurps.
Depending on which primers you use, they will flatten after firing.
CCI 250 primers do flatten a bit, but don't flow.
Pressures are around 60,000psi, which is well within the constraints of the T3