500 Express rifle question

[matt85]

I came across a double rifle chambered for 500 Express, with a somewhat strange regulating load.

The load shown on the bottom if the barrels is 68gr 570gr. 68gr of black powder with a 570gr bullet in a 3.25" case strikes me as strange because it would need quite a bit of filler. Its an unusually heavy bullet with an unusually light charge.

Thoughts?

 

[Huvius]

My guess that it is something of a nitro for black load or a “light cordite” load as they were known.
I see it’s a Jones under lever rifle so quite strong enough for a LC load all other requirements met.