"Miller & Val Greiss Double Rifle - 10x47R load data needed"

Hello all,

I just purchased another Miller & Val. Greiss Double rifle. Based on a chamber cast, I think its likely a 10x47R caliber. Although this was typically a target cartridge, I think in this case it was intended for small / medium game.

"Miller & Val. Greiss / Munchen" is engraved on each lock and an "LS" on the bottom of one the left barrel. There is no caliber marking to be found.

I'm trying to determine the correct bullet weight for 10x47R so I can load cartridges. The bores slugged at .398 - .399 inches. I have brass and dies and have loaded a few test rounds with 250g bullets that were loaded with AA5744 and IMR4198 powder, but have no data to use as a guide in determining what bullet weight and velocity are correct for this cartridge.

Any suggestions would be greatly appreciated.

Specs for the rifle are as follows:

Swing-Lever Double Hammer Double Rifle - Non-Rebounding Hammers - Engraved Receiver & Back-Action Side Locks - Barrels marked "LS" "12762" - Locks marked "Miller & Val Greiss / Munchen" - Gold Inlaid Decorative Breech Bands - 6 lbs 13 oz - 13-3/8" LOP - 24-13/16" Barrels - 1 Standing 1 Folding Leaf Rear Site & Pop-up Tang Site - Set Triggers (both) - Horn Swing-Lever - Spur Trigger Guard w/ Pierced & Scrolled Dark Horn Finger Rest - Steel Engraved Trap Butt Plate holds 3 rounds - Sling Swivels

thanks