My friend won a model 70 super grade in 280 Remington. Where would you start if using a 140gr Barnes tsx he is recoil sensitive. Will be used for plains game in RSA this year. Thoughts and suggestions appreciated

I'd load at (whichever powders I have) whatever barnes lists as starting load, and -0.065 off the lands .. with a fed 215M primer

My bullets of choice are 150gr Core Lokt and 150gr NPs. One shot kills on antelope, WTs, mulies, and 1 cow elk.

My youngest boy has a pre 64 Model 70 in .280 that we got from a member here on AR and great friend of mine that posts as "taylorce".
Last year when he was 11 and 12 years old I came up with a load using 139 grain Hornady GMX bullets which are a monometal very similar to Barnes. I developed this load for him to use on a Cow Elk hunt but it never came to be.
His load shoots well under an inch at 100 yards and sometimes half that, recoil is easy enough that a 12 year old handles it well from the bench in a very light rifle.
139 gr GMX, 53 grains of IMR 4350, WW or RP brass and CCI or WW primers.
2870 fps.
OAL was set same as factory RP green box ammo.
We have also used the same load with 140 grain Sierra's and it also shoots under 1" groups and he got 3 one shot kills on whitetails with it this last fall.
I would not hesitate to take this load to Africa on a plains game hunt.

The TSX is my go-to bullet for big game from whitetail to cape buff. For elk-size and above I'd lean to the 160 grain, but not hesitate to use the 140. Results for the 280 will not be noticeably different from the 7mm Rem Mag.

Go to JBM Calculator to play with recoil numbers.

SPEER data is very conservative. I'd use IMR 4350 at 52 grains and see how he reacts.