Argentine Mauser from 30-06

[ulav8r]

It has been a long time since I had a 7.65x53 that I formed brass from .30-06 for. You did ream the necks before loading, that is a good thing; in my experience either reaming or outside turning is required.

What I would do is form some new cases with the rifle there to try them in. Form until there is a slight resistance when closing the bolt. This way you don't have to try to load a projectile out to jam into the lands for headspace control.

Robert

Agree with Robert.

Robert

[AntiqueSledMan]

Hello CoRifleman,

I had a hunch, have some cartridges marked 7.65x54 SF 76.
Thought there might be a difference, but they seam to measure very close.
Mine are about (I say about because it's very hard to read the shoulder).
OAL 2.100", Base to Shoulder 1.775", Base to Neck is 1.870"
This is close to what I have for dimensions listed,
OAL = 2.100", Base to Shoulder 1.778", Base to Neck = 1.876"
The only issue I encountered was they were hard to chamber,
but after I started turning the necks, that issue disappeared.

AntiqueSledMan.

[CoRifleman]

Thank you all for the help here.

Yes I've got some of that sk75 ammo. That stuff is rough,like they had sand in the dies ha. Some corrosion, so I pulled the bullets (talk about a heavy crimp!) And dumped them.

I also have a 1909 carbine and a 1891 long rifle, so I think the "short" 1.8160 to datum cases I made with the die set will go in either of the other two, I just am going to get 50 cases made up for this oddball and then move onto the others.

If I had access to a lathe, I'd buy three of the lee sizers and just have one for each, knowing they're so long, I could trim them to length at press full contact. Maybe someday. I hate the idea of the time spent getting this die just right at 1.8250 in a lock ring and then spin it away for other rifles.

[CoRifleman]

Today's update...

Made 5 cases up to more closely fit the chamber...

3@41.5g, 2@42g.

Figured out true neck length, made these cases .020 short of contact, trim length ended up being 2.150. Lyman trim-to spec is 2.100.

1.8245/1.8250 shoulder measurement, which is 2ish thou back from contact.

For cartridge OAL I set the hornady cannelure to crimp correct, which put my ogive about .012 from the lands (much closer to the lands than spec 2.100 trim length and my previous 2.900 oal). New oal to tip is in the 2.950 range.

Cases chambered and fired well.

After firing, the 41.5 charge cases actually shrunk in length to 2.1490, the 42gr remained the same at 2.150 or grew to 2.1505. Shoulder measurements were in the 1.8250 range still.

Velocity was a smidge down to yesterday, which jives with a bit larger case volume.

But... The slight ring at the shoulder on fired cases is still there.

[15meter]

I load for an 8x50R in a double rifle, the neck comes out very similarly after fire forming 7.62x54R or 8x56R in the rifle. Being a double rifle it is easy to look inside the chamber. You can't see a visible problem but the necks come out looking quite similar. I've got some of the brass with probably a dozen firings with no problems. As a guess, every 5th loading the necks get annealed. Haven't lost any yet to neck splits or other maladies.

[CoRifleman]

Thank you 15. I also spoke to a local gunsmith, and he reiterated what many of you said.

A chip hung on the reamer, a broken reamer, re-reaming with a slightly smaller reamer will all produce this slight shelf. He said it's no big deal, AND it'd be all but impossible to fix without rebarreling. Just watch the brass and keep this brass only for this rifle.

You guys are a great help.

[jdsingleshot]

Looks like the chamber has a ring in the shoulder area caused by a nicked reamer at the Mauser Werk. If so, there is steel left sticking UP in the chamber as a ring. Touch the shoulder with a good reamer and the problem will disappear.

[Baltimoreed]

Cut a few weird cases lengthwise to inspect the interior, and a true sideview of the case, borrow a borescope to look in the chamber. Could also do a chamber cast with cerrosafe.

[gliebegott]

Anyone interested in some actual rounds of this caliber?

They would be free.

PM me

[CoRifleman]

anyone interested in some actual rounds of this caliber?

They would be free.

Pm me

yes!

[paul edward]

The best way to discover whether there is a chamber defect is to do a chamber cast. Alloy is available from Brownell's and instructions are available online.

Look for PM

[sse]

I have had a couple of rifles in the past 60 years that had fired cases that looked like that.
You can take 1 case and see how many times you can load it before it fails. I have saved time by doing that on rifles that I wondered about.
After 10 or so loadings I figured there was nothing to worry about.

[Hick]

The fired cases have been fire-formed
Neck size and load
Shoot
Have fun
Mike

This really important-- note Mike is saying "neck size." Regardless of any oddity of the chamber, if you have fireformed and then do not push back the shoulder-- only neck sizing, your brass is now custom fitted to the chamber and will work just fine. So do not push the shoulder back. There is no reason to expect the brass to separate here. (Not impossible but very, very unlikely). My 1909 Argentine carbine also has a slightly odd chamber, and the brass lasts for many, many firings, but neck sizing only.

Brass separation at the base is a completely different problem. It happens because the brass flows toward the neck in full length sizing, then it stretches again the next firing, then gets full length sized and the brass flows forward again, then streches again when fired-- until eventually it thins too much at the base and separates. Neck sizing prevents this because after the first firing it never grows.

[Reg]

Thank you 15. I also spoke to a local gunsmith, and he reiterated what many of you said.

A chip hung on the reamer, a broken reamer, re-reaming with a slightly smaller reamer will all produce this slight shelf. He said it's no big deal, AND it'd be all but impossible to fix without rebarreling. Just watch the brass and keep this brass only for this rifle.

You guys are a great help.

I would agree with your local gunsmith. I think he is spot on. Neck sizing and keep the brass for this rifle separate and a good neck annealing from time to time are all good ideas. One thing I question is the neck turning or reaming. Since about 1962 I have made thousands and thousands of these cases from 30-06 and even 270 cases and have used them in at least 20 or more different rifles and never once have had any apparent problems. No chambering problems, no signs of pressure, nothing. I am sure it makes no difference in brass life but it might save you a step.

[Hick]

I would agree with your local gunsmith. I think he is spot on. Neck sizing and keep the brass for this rifle separate and a good neck annealing from time to time are all good ideas. One thing I question is the neck turning or reaming. Since about 1962 I have made thousands and thousands of these cases from 30-06 and even 270 cases and have used them in at least 20 or more different rifles and never once have had any apparent problems. No chambering problems, no signs of pressure, nothing. I am sure it makes no difference in brass life but it might save you a step.

I'm with Reg on this. I make my 7.65 cases from 30-06 and 270 brass and have never turned or reamed the necks and had no chambering or other problems.

[leadman]

The original 1891 cartridges, along with some commercial cartridges made on worn out Argentine equipment was marked 7.65X54. Later when the bullet was changed to a Spitzer from a roundness the neck was shortened 1mm.
Some say there were 2 different cases with different headspace but I don't believe this was true. I think what was the case is that the extra barrels that Argentine bought (3 per rifle) had short headspace so they could be fitted and headspaced when a barrel replacement was needed. I have bought 5 or 6 of these replacement barrels and on the first couple I installed I just trimmed a shellholder to get the cases to fit. Now I have the reamer and headspace gauge and have adjusted the headspace on my six 1891s so they are all the same. I have a couple of these NOS barrels waiting for a couple more guns in need of them. There is a very long leade in front of the neck designed into the chamber so it is not not possible with some jacketed bullets to touch the rifling.
Graf & Sons normally has new PPU brass if needed. I wish they still sold the 150gr Hornady SST as it is very accurate.
I do not ream or turn reformed brass as the chamber dimensions are generous and this is not normally needed. I think it is an advantage to not turn or ream as far as accuracy goes.

[Uncle Grinch]

I'm with Reg on this. I make my 7.65 cases from 30-06 and 270 brass and have never turned or reamed the necks and had no chambering or other problems.

I’ve been forming 7.65 Argentine from R-P 30-06 brass for many years (20+) with a forming die and never have annealed or reamed the necks. I use R-P brass just so it is different from my HXP or Winchester. No issues with cast or jacketed bullets in either my 91 or 09.

[376Steyr]

"Some say there were 2 different cases with different headspace but I don't believe this was true. I think what was the case is that the extra barrels that Argentine bought (3 per rifle) had short headspace so they could be fitted and headspaced when a barrel replacement was needed."

That could explain how the ridge got cut in the chamber. Somewhere along the line, the rifle was re-barreled, and somebody used an under-sized reamer to hog out the chamber. It was probably "close enough for Government work and now let's go to the cantina and get some cerveza!"

[GONRA]

GONRA sez - don't worry about it! !!

[Larry Gibson]

I've been forming cases using 30-06 military for the 7.65 Argentine for many years. Back when available picked up several hundred R-P 8x57s that just need sizing in 7.65 FL die and a bit of trimming. With the 8x57 and LC M72 match '06 cases I don't turn or anneal the case necks. I have annealed when formed out of M2 cases though. I also have 100+ Argentine SF 85 cases I have converted to use SR primers in.

I currently have three M91s and a M1909 rifle. They all have a bit different head space so I keep the cases separate for each and just NS. I use a Redding 308W bushing die to NS so necks give .002 - .003 neck tension. I have also thinned a 1/2" nut to slip over the case to NS using a Lee .308W collet die.

Never really found that much difference in the Headspace on Argentine Mausers. I have always found them to be as much as .010 shorter in headspace than the 7.65 Belgian Mausers. The cartridges, both Argentine and Belgian, have the same cartridge head space though. That was the problem with Lee's early 7.65 Belgian dies. They seemed to size the cases be headspaced for the Belgian chambers and were too long to chamber in many Argentine rifles. Appears Lee has corrected that.