Re: sporterized mosin nagant M39
OP PM inbound. I am neither an idiot nor do I believe they should not be messed with. In fact I've modified a shit ton of Mosins,mostly M39s. Not to mention the Mausers,03 Springfields and every other Mil-surp that at one time or another had cheap ammo available. The reason I offered to buy and exchange for it is simply barring a couple other Finnish built Nagants, the M39 is the finest most accurate example. The others include the M28, predecessor to the M39, the M28/66 and M28/76 target rifles and my current project the TKIV 85 sniper rifle. The latter there is still in use by the Finnish military.
I built one M39 by making a side rail mount that required machining a flat on the receiver. This allowed an 8x PSOP Russian scope to be mounted,nice and low and slightly to the left. That optic has a BDC elevation turret calibrated to the 7.62x54 round. It was rather pleasant making first round hits at 800 meters with an old relic.
Another was done like a L39/42 Enfield with the forend shortened to the middle band. Another side mount but with a Picatinny rail this time. Same result.
I tell you this because I started working on guns by cutting up old military rifles. You obviously want to learn yourself and most here are supportive of that. The thing is those rifles are easily capable of shooting 1-1 1/2 inch groups at 100
yards, bone stock with heavy ball surplus ammo.
On that topic, the M39 was not designed specifically for the D166 projectile. If you inspect a bunch you will find many with a "D" marked barrel, on top of the barrel shank just ahead of the receiver. This meant they had had the chamber cut with a longer throat so the Finns could use the millions of rounds of 181grain heavy ball captured from the Russians. The Russians used this in their machine-guns. It's usually denoted by a yellow tip. They usually shoot very well with the lighter 147grain surplus that is still available cheap. If I can help just holler.