Resurrecting this thread since I have found some Barnes 300 Grain TSX. Wanting to find some good practice loads that have around .270 Winchester recoil levels.
I talked with Hodgdon , they provided .416 Rigby reduced loads for the .350 grain Speer but not on using the Barnes 300 grain TSX.

Interesting plinker, duplicating the rainbow trajectories of the bison hunting era.
Let us know how the accuracy is.

The 2020 HODGDON ANNUAL MANUAL uses just that load range with Trail Boss and the 350-gr Speer SP:

Starting Load: 25.0 grains >>> 1139 fps

Maximum Load: 35.0 grains >>> 1354 fps

No pressures given, obviously very low.
24" barrel of 1:16.5" Twist.
Primer: F-215
Norma case.
COL: 3.640"

Recoil in .416 Rigby with 35-gr charge and 350-gr bullet at 1350 fps for 10-pound rifle:
12.87 ft-lbs
9.10 fps

Recoil in .270 WCF with 57-gr charge and 130-gr bullet at 3110 fps for 10-pound rifle:
14.34 ft-lbs
9.06 fps
For 9-pound .270 WCF rifle:
15.93 ft-lbs
10.67 fps
And increasing recoil as rifle gets lighter.

A 10-pound .416 Rigby with Trail Boss will be a lot easier on a recuperating shoulder than a featherweight .270 WCF standard load.

RIP,
Thank you.

Anyone using AA5744 as a reduced load?
I only have one bottle of Trail Boss, and it looks as though it will be difficult to obtain more in the immediate future.

Now you are in high cotton.
I will vouch for a reduced load with AA-5744 for the .416 Rigby.
24" barrel.
Norma brass.
CCI-250 primer.
350-grain Speer SP, 3.640" COL.
AA-5744 34.0 grains >>> 1520 fps at 5 yards chrono, 5-shot st.dev. 18 fps with no filler.

10# .416 Rigby rifle recoil: 15.19 ft-lbs, 9.88 fps
By golly ! That is less than recoil of a 9# .270 WCF standard load.

Rip,
Thanks. Appreciate you sharing that, you provided a lot of detailed information.
That is exactly what I was hoping for. TrailBoss has mostly been hoarded, and I have just one bottle. Right now while I am healing up , a .270 Win is at my current recoil limit. Having a .416 Rigby kick like a .270 Win especially off the bench will be great! I am hoping I can start shooting full power loads next year.

Bringing this up again . Curious if anyone has a reduced load for the Barnes TSX 300 grain

According to my software package 50 gr. of 5744 will deliver the 300 gr. TSX at 2100 fps while generating 27k PSI.