August 2020 update:
Late due the Wuhan virus follies.......etc.
Have sourced bullet drawing dies from Corbin and Lee to squeeze standard .25 caliber .257” bullets to fit.
Chose the Nosler 100 grain Accubond and Speer 100 spitzer flat base soft point for trials.

The rifle had to go back to Steve Bertram to have the throat deepened as current bullets sized down would not seat out to proper cartridge overall length. The rifle now has a nice target rifle grade throat and case necks only need a light reaming.
As there is no current or vintage ammo and no original Kynoch .242 bullets available I don’t consider this throat alteration to be of huge consequence to the original rifle and does allow it to be shot with modern components.

Weather permitting this week I’m going to work up a load with IMR 4350 and the 100 grain bullets to get close to the vintage advertised velocity of 2800’/sec.
This rifle has a 24” barrel and the original Kynoch advertised velocity was likely obtained with a 26” or 28” barrel so 2750’/sec might be a sweet spot.

- Mike