8x50R Aus Forming Issues

[TheAbe]

I picked up an M95 straight-pull chambered in 8x50R a few months back, and I’m to the point of making brass for it. I have a set of 8x50R dies from RCBS, and have followed the procedure mentioned to make brass from trimmed 7.62x54R brass, but for some reason the rounds (unloaded at this point) won’t chamber without tapping on the bolt handle with a hammer, and I really don’t want to do that.
I will be making a chamber cast this week to confirm the chambering, but the only thing I can think of at the moment is that I’m using Norma brass instead of the PPU that most people are using. Is there a known difference in rim dimensions between PPU and Norma 7.62x54R brass? I did grind down the rim a bit, but it didn’t make much difference (took it down to match the 14.00 mm diameter of my surplus 8x56R rounds I’m using as a rim reference).
Suggestions? Anyone have similar issues with their 8x50R M95?

[hpbear101]

I have one rifle in this chambering and made my brass out of PPU with no issues. The necks were a little long but I found they chambered fine. I would suggest coating one of your cases with a black sharpie then try chambering it, you should get an indication of where it isn't sized properly. My guess would be either the shoulder isn't set back far enough or the base (forward of the rim) is too large. If its not setting the shoulder back enough make sure your sizing die is all the way against the shell holder you should feel it "cam over" on the sizing stroke. If that doesn't take care of it you could turn a little off the base of your sizing die. If the base is too large I would use a lathe and turn the base to fit (you could use a drill and file).

Tom

[15meter]

Maybe a shoulder issue, when I was forming 8x50R brass, I ground ~.010" off the top of a shell holder to use during the initial forming. Using the thinner shell holder allowed the shoulder to be set back a little more, allowing the case to chamber. After first firing the ground shell holder wasn't required.

It's something to try. I formed 8x50R from both 7.62x54R and 8x56R.

I still have a bunch of the formed brass, it shot extremely well out of my buddy's double rifle. Lost him to cancer 9 months ago.

I've considered trying the 8x50R brass in my 8x56R straight pull rifle, don't know how a 6mm shorter neck will work.

Brass is too nice to scrap.

[TheAbe]

I do have a differently-branded shellholder. I’ll chamber cast, ink my brass, and grind a shell holder to see what difference it makes.

[15meter]

And I prefer grinding down a $5-10 shell holder as opposed to going after a much more expensive sizing die. The dies I used were RCBS and not particularly cheap or easy to come by.

Either method will work, the shell holder is just easier to replace.

I've got a stationary belt/disc sander, it's just a couple of seconds to shorten a shell holder. I've done it to a number of different shell holders over the years.

[Larry Gibson]

If you're allowing the press ram to "cam over"....don't. Screw the FL die in further until the shell holder bumps solidly against the bottom of the die w/o the ram or press handle flexing as if wanting to "cam over". Also make sure the decap rod isn't bottoming out on the inside of the case.

[TheAbe]

I took a chamber cast today and it appears the shoulder of the chamber is about 2mm back from where my reformed cases have their shoulder. Everything else should fit my cases. That being said, putting one of these 7.62x54R cases through the 8x50R die it does not appear that the shoulder moves at all. That explains the shoulder location, which should be about 1.6mm further forward on the Russian case. I’ll be grinding my die down a bit tomorrow and see what results. Lots of work going on this week in various categories...

[TheAbe]

Grinding did not proceed as planned, but here are some photos of the chamber cast. For reference purposes I’m also going to list the dimensions I’ve found for the 8x50R Austrian case, all in mm:

Overall case length: 50.38mm
Neck length: 6.30mm
Shoulder length: 5.93mm
Body length (including rim): 38.15mm
Rim thickness: 1.38mm
Length with bullet: 76.21mm
Neck diameter: 8.90-9.03mm
Lower shoulder diameter: 12.01mm
Base diameter: 12.48mm
Rim diameter: 14.11mm

From these numbers the distance between the top of the rim and the start of the shoulder should be 36.77mm. Since mine is at 36.93, that’s right about where it should be. The question is: why is everyone else able to chamber 7.62x54R cases when the shoulder of that case starts 38.1mm from the rim? Does my M95 just have a tighter chamber than most? There is a marking on the receiver noting the factory head spacing adjustment, and while I can’t recall exactly what it was at the moment, I recall that there was a significant length of barrel that was called to be trimmed to adjust the headspace when the rifle was new. Any thoughts anyone?

On the up-side the casting confirms what appears to be strong rifling...I want to say 8.30mm groove diameter and 8.14mm lands diameter. Below photos of my chamber cast and of a 7.62x54R case I bought to convert...

[kywoodwrkr]

Before you grind on shell holder, is there enough space between bottom of case and shell holder to insert a .010 feeler gauge or feeler stock?
A lot of shell holders have different rim depth space cut into SH.
ymmv

[TheAbe]

Did some more experimentation and am still puzzled. Can a few fellow members who successfully load for 8x50R (Austrian/Hungarian) measure for me the distance from the top of the rim to the start of the shoulder tapering on their brass that does chamber? It’s either the rifle chamber, the brass, or the dies at this point, and I’m trying to check what others’ dies and chambers are producing.

[15meter]

Wish I still had access to an optical comparator, that is the best way to get the measurement you want. That said I'll try and get a measurement with a digital caliper.

[Moleman-]

Sos when you colored/dykem/sharpied the case and tried to chamber it like hpbear101 suggest, where was the coloring worn off the case? That will show you where the issue is.

[WILCO]

My guess would be either the shoulder isn't set back far enough...

That's my guess.

[TheAbe]

Sos when you colored/dykem/sharpied the case and tried to chamber it like hpbear101 suggest, where was the coloring worn off the case? That will show you where the issue is.

Finally sharpied both one of my die-formed cases and a dummy 7.62x54R case (both with projectiles and nothing else) and loaded them in. In both cases there is a scrape-ring 1-2mm forward of the start of the shoulder.

So...I'm suspecting the die. Going to send an email to the manufacturer...

[hpbear101]

Any chance the dies could be for a different 8x50 case like a Lebel? Also if it would help I would be happy to send you a few pieces of my formed brass to compare.

[TheAbe]

The die cartridge is certain: manufacturer sent them to me directly, they’re stamped, and that manufacturer does not make Lebel dies. I did email them last night, so we will see what their response is. It is possible there was a minor error, as taking my calipers out and removing the decapping pin/expander the shoulder appears to start in the die approximately the distance from the die mouth that it should be from the case rim. That would cause the discrepancy to be exactly the width of a shell holder which is about what I’m seeing. I experimented a little with hammering an unformed case into the empty die but I got the order wrong and messed up the case. For my own notes, my order needs to be: trim case, form with pin to widen neck/mouth, remove pin and use mallet to set shoulder, measure, flare mouth, load projectile, test in chamber...

[TheAbe]

If that still doesn’t work, yes, the brass for comparison would be appreciated, but let’s see what I can determine with what I have and what the manufacturer says.

[Moleman-]

Finally sharpied both one of my die-formed cases and a dummy 7.62x54R case (both with projectiles and nothing else) and loaded them in. In both cases there is a scrape-ring 1-2mm forward of the start of the shoulder.

So...I'm suspecting the die. Going to send an email to the manufacturer...

Sounds like the non fireformed cases are hitting where the ring is. I see in your process outline that annealing the necks/shoulders was absent. Often when pushing back a shoulder on a case they will be springy and end up too long for me to chamber unless they're annealed. Still though on some 8x57 cases formed from 270win I was getting this from annealed cases so I trimmed a little (0.010"ish) off my sizer die which fixed the issue. 0.010" isn't much, it's about the thickness of 2.5 sheets of computer paper.

[TheAbe]

Shame on me for forgetting my basic metallurgy. I was thinking annealing was only useful for preventing case failures, but thank you Moleman for reminding me the elastic modulus and the maximum elastic strain also can increase with prior plastic deformation. Since these are once-fired cases, they’re probably over-worked and only elastically deforming when force is applied in the die at the shoulder (neck stays deformed because the deformation is greater).
Ok I’ll anneal and report back. Hopefully I’ll get a chance to this weekend.

[TheAbe]

Whelp, the annealing didn’t make a difference with shoulder position. Manufacturer wasn’t much help either: just told me to make sure I had the die seated far enough down, and something about brass flow messing up the headspace if I don’t have the die far enough down. Do they realize this is a rimmed cartridge? Anyway, I need to find someone with a lathe locally to turn down the die about 2mm...