I received some PPU Nagant revolver brass by accident and wondered if they could be used in a rifle with bullets seated out beyond the case mouth.  I sectioned some cases and found that the web and case walls were actually thicker than those typically found in the .357 Magnum.  This gave me hope that I could safely exceed the nominal pressure rating of the 7.62 Nagant cartridge with these cases when used in a rifle.  I have no information on other brands or lots of 7.62x38mmR brass.

I cranked up QuickLOAD and started looking at what velocities might be achievable.  I looked first at cast bullets.  Output suggested that bullets like the 308-165-SILH or 30-180-FN could be driven fast enough to remain supersonic at 300 yards.  This supported the idea that I could use the rifle for high-power practice with our club owned ShotMarker electronic target systems.
 
I worked out a set of chamber and throat dimensions and sent them off to JGS.   I gave JGS the name 30 SSR (Single Shot Rifle) for the reamer.  I have built many rifles, mostly for competition applications, but never one using a falling, rolling, or tilting block action.  I decided to go with a CPA 44 ½ action and gathered up the other parts to build the rifle.  I have had the rifle complete since early 2022 (picture attached) and now it is finally shooting very well (MOA 10 shot groups) but not with the heavier cast bullets which tended to produce vertical or diagonal strings.  The first really small groups were produced with 125 gr jacketed spitzers.
   
I should quit while I am ahead and use light jacketed bullets, however, I suspect the key factor is bullet weight, not construction.  I am securing molds to cast lighter bullets for testing.  I worked hard on the heavy bullet loads producing some very narrow but tall groups.  I would be very interested in your comments on why this rifle would produce vertical or diagonal stringing.

I also learned a lot about this type of single shot rifle and how to produce more accurate ammo.  I would be happy to report on the 30 SSR rifle build, reloading die fabrication, or load development if anyone has questions.

frnkeore wrote on Nov 26^th, 2023 at 12:14pm:


Here are the specifications. I once thought about doing the exact same thing as the OP. I had a bunch of cases but I gave them to my friend to turn into to 218 Bee.

Sounds about midway between my 30 ELCO (357 Max, necked to 30 cal) and a std 32/20 (.308 groove).

I used 10.5 gr of #9 with a 187 gr bullet and my wife uses 9.5 gr, #9 or 10.2 gr 296, same bullet. All are 1400 to 1450 fps.

Edit:
I forgot to mention that my 30 Elco is 1.9cc.

The following 30 SSR loads seem to work for my rifle.  Please be careful, they may be completely unsatisfactory and/or dangerous for you.  Powder charges, projectiles, and overall lengths are not applicable to loads for Nagant revolvers.

Promising load #1
.308-165-SILH, linotype, body sized 0.310, nose sized 0.300 (using modified NOE sizing tools)
11.4 gr. SR 4759
Murom KVB-5.56M primer
OAL 2.260
Velocity 1590 fps, SD 11 fps
One five shot 100 yard group, 1.70 x 0.30.   
A picture is included, the double is the lowest hole.  This is one of the smaller groups showing the characteristic shape of many of my cast bullet loads in this weight range.  I still hope for comments on what might be causing this shot stringing.

Promising load #2
123 gr. 0.310 diameter PPU SP
13.5 gr. Vihtavuori N110
Murom KVB-5.56M primer
OAL 2.168
Velocity 1980 fps, SD 14 fps
I have several 100 yard 10 shot groups around one inch with the same or similar loads.

I found the LEE #19 shell holder worked best for these cases.  I use LEE M-Dies, or LEE Universal Expanders with replacement stepped expander plugs from NOE.

Hello frnkeore.  Thanks for the reply.   

I have H110.  The 7.62x38R case is right is the size range of the 30 Carbine so H-110 might work well.  I have burned lots of H110 in revolvers and grew to dislike it for those application.  I found it very sensitive to load density often with high standard deviations.  It does work better for me in rifle barrels (M1 Carbine).  Do you have loads for similar cases with H110 or other ball powders that you could report?

Thanks frnkeore for the H110 load suggestion.  Using QuickLOAD and the RCBS 30-180-FN, a charge weight of 12 grains of H110 produces a max pressure comparable to those that are calculated with other powders I have tested in the 30 SSR case.  Calculated velocity would still work for my 300 yard shooting.

I did note that the calculated filling ratio is under 83% for this 12 grain charge of H110.  In other cases where H110 produced workable loads for me, the filling ratio was always right around 100% (30 Carbine, 44 Magnum, 357 Magnum).  Long ago I did try H110 (296) in the 22 Remington Jet Magnum based on loads listed in at least one reloading manual resulting in triple digit extreme spreads in velocity.  Max loads listed with H110 in the Jet were well short of 100% filling ratio.

Manufacturer’s recommendations and many reports indicate that reduced loads and/or low filling ratios are not recommended and may be dangerous with 296/H110.   Based on your loads, you must be having success with H110 at low filling ratios.  I wonder what could explain the difference.  Could it have something to do with breech seating vs the use of fixed ammo, or the thin walls of the 32-20 cases producing quicker or better sealing?  Do you use a filler in your 32-20 loads?  What extreme spread or standard deviation do you measure with your loads?

The cast bullet association back in the early days  in the 308 18-19g of 296/H110 was popular and we all burned lots of it.(The RCBS Cast Bullet Manual had loads for  the 308 and some other rifle cartridges ) 
Ed Harris sent some loaded ammo to Olin to test and they weren't comfortable with the pressure variations IIRC and didn't recommend it.Most if us kept using it with no issues and stellar accuracy though.

Curious, I did not see twist of barrel? Also what does your bench set up look like. If your getting tight narrow groups that are vertical stringing it doesn’t completely sound like load. Jmo