8x50R Aus Forming Issues

[junkbug]

Does unfiered 7.62x54r cartridges fit in the chamber ok?

[Moleman-]

I was hoping the annealing would do the trick for you. You don't suppose they sent a 8x56R or a 8x50 Lebel die mismarked as a 8x50R do you? Your chamber cast looks like a 8x50R which has more of a shoulder than the 8x56R. I'd be tempted to do a casting of the die to see what the ID of it measures.

[TheAbe]

I haven’t had the ability to test any, but FL-sized 7.62x54R does not fit...hits the shoulder.

[TheAbe]

I was hoping the annealing would do the trick for you. You don't suppose they sent a 8x56R or a 8x50 Lebel die mismarked as a 8x50R do you? Your chamber cast looks like a 8x50R which has more of a shoulder than the 8x56R. I'd be tempted to do a casting of the die to see what the ID of it measures.

I don’t believe the manufacturer makes 8x50R-Lebel dies, nor 8x56R dies. My chamber cast does look like an 8x50R vs an 8x56R (and 8x56R won’t chamber anyway...got some “free” with my en-bloc clips).
One other possibility is that at one point, this rifle may have had its barrel removed and re-attached...what would be the result if it were tightened one revolution too much? Would that effectively shorten the chamber 1 thread width? Is that even a possibility? I’ve never removed or attached a barrel before and am uncertain what all goes into the process of head spacing for a rimmed-cartridge rifle barrel... any input from those whom have?

[36g]

A rimmed cartridge should headspace on the rim, not the shoulder. The chamber can actually be somewhat sloppy from that standpoint as the shoulder just needs to allow the cartridge to chamber. Critical headspace dimension is the rim thickness in relation to the bolt face.

[TheAbe]

On suggestion of a member I tried taking a formed case, removing the decapping pin, and pressing it back on the die on top of the shell holder. This helped, but a dummy round still won’t quite fully chamber. The case revealed scratches mid-shoulder now. I’m going to try new PPU brass, since that’s what everyone else seems to be having success with, and if that doesn’t work the die is going to be trimmed.

Has anyone else had issues with a new 8x50R die they purchased in the pst few weeks?

[TheAbe]

Does unfiered 7.62x54r cartridges fit in the chamber ok?

Took the dies, casting, and formed cases to my lgs for advice. After a bit of discussion and measuring he gave me a few loose unfired 7.62x54R Winchester brass he had laying around to experiment with. I’m hopeful as the shoulders of these unfired cases seems set back about as much as they need to be. Will Test as soon as I’m able.

[TheAbe]

Ok, new angle: this is a photo of the chamber as best I could do with my phone. Is that a bit of broken extractor wedged in there? The shiny bit sticking around the rim and back into the cutout for the extractor (upper right in photo depending on orientation.). It doesn’t interfere with the extractor when nothing is in the chamber but if that’s piece isn’t supposed to stick there, I’m thinking that might be smashing against the rim of the cartridges when chambering.
I suspect this because my latest experiments had me pushing back the shoulder of my cases using an 8x50R Lebel sizing die, which has the shoulder back a few mm even from the 8x50R Austrian.

Any suggestions for removing this if it isn’t part of how the chamber is supposed to be shaped?

[fgd135]

You've probably already tried this, but have you ever thoroughly cleaned out and polished the chamber? Is it at all possible that the chamber of your rifle is either slightly pitted or rusted? A good cleaning with a brass brush chucked to a short cleaning rod and cordless drill might be needed/might be a burr or rusty spot that is inhibiting the chambering of your new cases. There are other posts on the site regarding chamber cleaning/polishing.

[Rockindaddy]

I had the same problem using 54R Norma but chucked the sizing die up in my tool room lathe. It fit in a 5C collet. I used a carbide cutter to remove .012" off the face of the die. Worked great! Most rifle sizing dies are case carburized. You can't machine em with a high speed cutting tool. Have to use carbide. Don't forget to put a slight chamfer on the inside face and polish with some emery cloth.

[TheAbe]

If only I had a lathe....one of those long term life goals. Or maybe I should inquire with my cousin who has a few. Either way, I’ve ordered an adjustable hand reamer of the size range of the rim. Hopefully that’ll suffice to slowly grind out or cut out the obstruction without damaging the chamber.

[TheAbe]

Some success with a rotary file against the obstructing bit. I can now chamber dummy rounds with a rim diameter under 14.20mm. I’m going to work at it a bit more to ensure I don’t need to grind all my case rims down.

[TheAbe]

I think I found a solution and what the problem was in the first place, and that is extremely tight headspacing, which on a rimmed cartridge is the thickness of the rim. The solution: grind off the beveled part of the base of the 7.62x54 cases before sizing/forming, or after, it doesn’t really matter. PPU brass has a bit thinner rim to begin with so it’s easier for me to get to the proper point, but both they and the Norma (and the couple of Winchester cases I have) all need to be ground a bit to reliably chamber and they reliably chamber. See below, left case will chamber and is ground, right case will not chamber fully.

[hpbear101]

Does that have any effect on seating depth of primer? Usually you would reduce rim thickness on the forward surface of the rim.

[TheAbe]

Does that have any effect on seating depth of primer? Usually you would reduce rim thickness on the forward surface of the rim.

If I’m lucky, I’ll get the chance to find out tonight when I try to prime some of these cases and load. I don’t have a tool to effectively reduce the forward surface of the rim.

[TheAbe]

In continuation, primers were still able to be seated “deep,” so no, this didn’t really impact seating of primers noticeably. 32 primed cases are now awaiting some test loads. Going to work up to 38gr of 3031 under 220gr 8mm Hornady spire points. I hear this can be a good, accurate load in these carbines.

[hpbear101]

Good deal. Post a thread on how they do

[TheAbe]

I’ll get more photos posted soon, but I was FINALLY able to take my M95 to the range last night and start testing rounds.
The good:
1) the rifle functions and nothing broke.
2) the bore appears excellent, and all holes were clean circles (no keyholing, yay!)
3) the bore is agreeable to .323” bullets. All shots fired were with the sadly discontinued 220gr Hornady Spire-Points in 8mm.
4) untrimmed (54mm long) cases seemed to function just fine....though maybe this contributed to the sticky extraction issues. I will experiment further.

Now the not so great:
1) I was only able to test 15 rounds
2) the 8x50R feed ramps do NOT like spitzer bullets. Inserting a full clip guaranteed a difficult time getting the first round past the front of the feed ramp.
3) I started to get significant case bulging at the third step of my work-up. I’ll have photos of these later, but the bulged cases were very tough to extract.

Takeaways:
1) the current bullets should not be loaded past 35gr of 3031 for my M95, and sticking to 34.5 would probably be even better
2) I really need to find some good, heavier round-nose 8mm bullets. A quick check shows that the heaviest that appears available is 170gr, though some CBS over 220gr are also around. These should suffice if they are gas-checked.
3) I should further investigate if the case length has a major impact on extraction of the fired cases (see if there’s a difference if I trim them a it). I also need to inspect the fired cases carefully for variations.
This was at 25yd, offhand, so the grouping doesn’t mean much other than the rifle is capable of stabilizing this bullet and decent accuracy may be a possibility. I was more focused on the rifle function and extraction than on placing shots in the exact same spot.

[hpbear101]

Glad to see you got it up and running!

[TheAbe]

So, upon closer inspection, the cases aren’t actually bulged from hat I can tell, but several have a divot in the side approximately 4mm behind the shoulder. Looking at the rifle itself, there appears to be a shard of metal in the chamber where the divots are, which are about in line with the extractor. All of the cases are intact (no missing metal), so I’m thinking firing the rifle dislodged that bit of metal that was adjacent to the extractor before, or part of it anyway. I shall clean and continue testing the next time I head to the range.
Also, many of the case mouths are a bit dented, so I will try trimming my next batch down to 50mm as it should be and see if there is any difference in the dents or extraction.