My first big game rifle was a 280 Rem CS (22" barrel) and it took the brunt of my reloading experiments as well. That was many years ago, but my pet load was;

139 gr. Hornady SST
57 gr. IMR 4831
WW Nickle brass
Fed 215 primer
COL = 3.345

It put them into 3/16" and I'm a poor shot. The rifle was stock except for a free float and glass bed.

These are all from the same rifle,

140 Nosler Part.
57 gr. RL 19
RP brass
210 M primer
COL 3.275 ...... .75 groups. (3035 fps)

150 Nosler Part.
57 gr. IMR 4831
210 M primer
WW nickle brass
COL 3.30 ........ .25 groups

160 Sierra BT
53 gr. RL 22
RP Brass
WLRM primer
COL 3.275-3.280......... . 75 groups

139 gr. Hornady SST
56 gr. IMR 4350
WLR primers
COL 3.33 .......... 1" groups

139 gr. Hornady SST
56 gr RL 22
WLR primer
RP brass
COL 3.33. ......... .25 groups

150 gr. Nosler Part.
56 gr. RL 22
RP Brass
WLR primer
COL 3.310........ < 1"

This is what it shoots now,

140 gr. Barnes TSX
57.5 gr IMR 4831
RP brass @ 2.530"
WLRM primer
COL 3.250" ........ .5" groups

And a varmint load,

100 gr. Hornady HP
60 gr IMR 4350
WW Nickle Brass
WLRM primers
Gave .5" groups @ 3320 fps