Tried 200gr Hornady JSP bullets and 4198, without filler, using magnum rifle primers. Results were very good accuracy from the left barrel (clover leaf, at POA), and OK results from the right barrel, ~2" to the right, with shots in 1.5" group at 30yds. Velocity averaged 1969fps, but with significant variation.

Accuracy results with 180gr Remington JHP bullets were very similar to the 200gr Hornady JSPs, but not as good. Strangely, the variation shot to shot in velocity was much smaller than with the 200gr bullets (powder and primer were the same for both.)

Very happy with the results I got deep cleaning the bores with Wipe-Out foam. Tremendous improvement over elbow grease and Hoppes. I think a further round with Wipe-Out may actually have these bores shining.

One fun fact that many of you with German doubles already know -- don't set the rear trigger before touching off the front trigger as the gun will double on you. Thankfully this wasn't a heavy recoiling round.

Next step is to try filler. I have both natural kapok fiber and vegetable-based packing peanut foam available. Will go with the kapok first, based on what I was reading from both Sherman Bell and Graeme Wright.

Will also try increasing the load slightly as the barrels are not crossing and there is 2-3" between left and right impacts. Factory ammo is at 640 meters/sec or 2100 fps, and I'm still 130fps below that, so hopefully more velocity will bring the right and left closer.

https://www.sellier-bellot.cz/en/products/rifle-ammunition/rifle-ammunition-sp/detail/240/