Since i'm sure I'm not the only one who owns one of these, I thought I would share a few thoughts on my reloading endeavors.
Let me start by saying that I have a Swiss model 1882 and a Swedish model 1887. Both are chambered in their respective 7,5mm cartridges and appear to be used very little. I knew when I got into these two that the cartridges were nearly identical, and interchangeable. The difference between the two revolves around the type of bullet used. The Swiss using a inside lubricated bullet, around ,315 in diameter ( I have heard specs ranging from ,312 to ,318), while the Swedish Nagant model 1887 uses a "heeled" bullet, the heel being ,311 and the body being ,325 at the driving band (measurements from actual Swedish Norma samples that I have).
The two guns that I have show nearly identical chamber dimension. I found this surprising, because I expected the Swiss revolver to have a proper throat, like modern revolvers, while I expected to find the Swedish revolver be bored straight through around ,325, very much like the 41 Long Colts of yesteryear (Bored straight through at around ,400). What I found was quite different. Both revolvers have internal cylinder dimensions that are nearly identical. Starting at around ,355 both chambers "taper" down to around ,327 at the muzzle end with no discernible throat, the Swiss being just a hair over a thousandth tighter. Measurements just in front of the case mouth measure ,341 in both revolvers. Bore diameter was a different story, with the Swiss having a very tight ,3055 groove and the Swedish having a more common ,312 groove. Holy smokes! Now I have reloaded and messed around with quite a few old guns with somewhat strange dimensions, but this may take the cake.
So my first thought was a call to Veral Smith. He owns/runs LBT molds and has probably contributed more to the art of casting bullets than most, so I trust his opinion, and even he was a bit suprised by such strange arrangements. I'm sending out some samples and measurements today, and should have a mold made that matches the look of the original heeled bullet and provides the best accuracy possible while being able to freely chamber in any of these revolvers. So in the mean time I set out to see what I could come up with. I've got quite a few molds, but I can't say that I have very many heeled bullet molds with a ,311 heel and ,325 body. Now call me crazy, but no one seems to be making one these days, or for that matter ever, as far as I know. So I dug out an old Ideal single cavity 31950. I can't remember what I even bought this mold for, but the size and weight seemed to match the original Swiss bullet pretty well. So I sized some ,318 and set out to see what happened. Without going into great detail, they were all over the place, in both revolvers. Accuracy was terrible no matter what load I used. Time to try something else. I will say, though, that I did learn one important detail from shooting the inside lubricated bullets. After the cases are once fired, they have dimensions that are a bit larger. Yes, I know that is what happens to every fired case, but the difference is that the case mouth and top half of the body retain these larger dimensions even after full length sizing. (I'm using the Hornady 7,5 swiss ordnance 3 die set). All of a sudden my sample bullet with a ,311 heel wobbled all over the place. Snug fit went from a ,311 heel to ,316. Nice to know, since I was going to order a custom mold with a ,311 heel. So looking through the mold selection, I decided to go a different route. I have a RCBS 08-110-RN mold designed for the Nambu pistol. I had some made already so perfect. I took a ,316 H&I sizer die for my RCBS Lube-a-matic and set it so that only the bottom, thick driving band was sized. Perfect! Now I have a heeled bullet, ,316 at the heel and ,324 at the driving band, and weighing only 6 grains more than my sample norma bullet. Loaded some up and accuracy increased 10 fold, with both revolvers around 2 1/2 inches at 30 feet off hand. I think that this bullet would work even better when casted out of very soft lead. I didn't have the time the other day, so I used the ones that I had which were air cooled wheel weights. I'm waiting to see what Veral makes for me. Hopefully even better. I've attached a picture of the Nambu bullets attached to the 7,5 cases, properly crimped. I used a top punch for the 31950 which created a cool flat point. Hand lubed with Lyman Ideal lube. I would imagine Lee liquid alox would work fine also, but this just looks cleaner to me.
Just though I would share some thoughts since almost no reloading info exists on these cartridges.