What the heck is a .243 J.R.P??

[titus123]

Ok so I have a rifle built on a Whitworth Single shot Mauser action. And it's chambered in .243J.R.P. Has anyone ever heard of this caliber.
The cartridge is .270 Winchester necked down to 6mm. The problem is that it is not a 6-06< different length,headspace.etc>
I called Mr. JRP the maker of JRP bullets and he can't remember anything about it other than he designed it in the early 80's.
Any and all help with load data, general information, or helpful hint as to where to start load development would be greatly appriated.

 

[dlutter]

Tough deal when the designer can't even remember anything. Good luck with your search.

 

[titus123]

The worst part is only 30 rifles were even chambered for the round. But in his defense he is almost 90 years old.

 

[bohemR13]

I'd try some lower 6-06 loads on it to start out. If there's minor differences in headpsace or shoulder length or something like that compared to the 6-06 the starting loads will still be safe.

Please take good notes as you work up to it so that other 6-270 owners might use it to build from.