The 416 Taylor rifle I loaded the 410 Woodleigh bullets was an unknown barrel manufacturer but built on a Mauser Model 98 action. Barrel length is 25 inches.
Landed on the following two loads to test: 74 grain of RL-17 and 75 grains RL-17 for each of Woodleigh 416 Rigby 410 grain RN SN bullets and corresponding 416 Rigby 410 grain FMJ bullets. I also loaded up some of the 350 grain 416 Barnes TSX bullets that came with the rifle and used 73 grains of RL-17. I did also purchase 75 rounds of Norma 416 Taylor brass from Prophet River Sports in Lloydminster, Alberta, Canada. I annealed and fire formed (using cream of wheat), Hornady 458 Rem brass and sized to 416. COAL of the Woodleigh bullets is 84.43 mm and 85.54 mm for the Barnes 350 grain.
To crimp, ended up getting a Lee Factory Crimp die specific for the 416 Taylor from a store in Pretoria, South Africa (RSA) which I picked up with my son passing through during a hunt in RSA just before the lock-down at the end of March 2020. This item makes the perfect crimp and is truly a unicorn - perhaps one of a few left in the world and in stock at safari outdoor for 150 Rand (
https://safarioutdoor.co.za/416-taylor-lee-factory-crimp-die-g00110927.html).
RL-17 I believe is a good powder for short magnums (N.B. - I use for my 300 WSM loads) and is not reportedly as temperature sensitive as RL-15, its predecessor powder for such applications. I waited for a good hot day to test (which in the foothills of Alberta at 28 Celsius is as hot as it gets). Results as follows (100 yard target range):
The 350 grain bullets made a tight grouping at 100 yards (O.5").
The 410 grain Woodleigh RN SN grouping with 75 grain RL-17 came out at 1.12 inches and the FMJ very close. I believe the rifle is capable of better accuracy - i.e., it took me my surprise the roar of this fire breathing dragon compared to shooting my my muzzle braked and tamed 300 WSM. There were no pressure signs including bulged or deformed brass, primer flattening or difficulty in removing spent rounds.
Measured velocity using a friend's Magnetospeed and happy with the reproducibility of the 75 grain RL-17 loads: i 2,346 ft/s; ii 2,359 ft/s; and, iii 2,354 ft/s (SD of 6.5). So I have achieved 416 Rigby performance with the Taylor!