Home Forums Reloading Big Game Rifles Shooting 7x57mm ammo in 8x57mm Mauser

This was moved down from the 'Ask The Gunwriters' section in hopes of getting more detailed responses...

I have a new-to-me Yugo 24/47 in 8mm mauser. The rifle is in excellent condition with matching numbers. I also have a couple hundred rounds of 7mm mauser standard pressure factory loads. A few questions...

Is is safe to shoot the 7mm mauser rounds in the 8mm mauser rifle to obtain 8mm mauser reloadable brass? If it is safe, is it likely to cause a lot of copper fouling in the rifle?

If it is not safe, can I pull the 7mm bullet and leave the factory charge and use some type of plug in the neck case to create enough back pressure to fireform the case? What should I use for the plug?

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Perhaps someone will respond to help me further my education on this subject...

My understanding is that when a beltless and rimless case with a shoulder that is too short for the chamber is fired, the case drives forward from the blow of the firing pin, ignition occurs, the case expands to the chamber walls while temporarily sticking to the them and the case then begins to elongate backwards toward the bolt face. This can be a primary cause of case head separation when the tolerances are too great.

If this is true then what would happen in the following scenario with a 7x57 in a 8x57 chamber? You are using a CRF bolt that captures the case with very little slop. You fire a case that has practically the same dimensions except the shoulder is about 0.01" short. Wouldn't the case flow forward primarily in the shoulder and neck area because the rim is captured by the CRF bolt?

Thanks for your time in dicussing this.

<>< Brian

I watched a man shoot a man shoot a .270 in a 30-06 one day by accident. Nothing bad happened but it did split the case neck. I bet the same thing would happen with every round you fired. IMO, I think he was very lucky. The way a rifle keeps gas contained is by using the case as a gasket to sill gas away from you the shooter. If there is no back pressure on the case there is a chance hot gases might escape in the action.

My advice would be not to do it. You can buy a bullet puller for $20-$30. pull the bullets and full length resize in 8X57 dies.

Terry

Back in my young and foolish days I purposely shot a 270 Winchester cartridge in a 30/06 chamber and there were no ill effects. Since the bullet to bore fit is sloppy the pressure will be lower. I think you could to it till the cows come home without danger to yourself but I suspect that repeating this excessively could damage the bore.

As for the 7X57 in the 8X57 question, without looking at cartridge diagrams, if the shoulder of the case starts in the same place as the 8X57 and the fit of the cartridge in the chamber isn't sloppy, you could safely do it. If the 7X57 cartridge fits a little loosely in the 8X57 chamber, either the firing pin won't touch off the primer or you could get a cartridge head separation.

I wouldn't do what you propose. A better plan would be to either buy 8X57 cases or to pull the 7X57 bullets and resize the cases to 8X57 with the appropriate die.

Thanks for the feedback.

If you're really wanting to use those cases, just pull the bullets and powder and run through an 8x57 full length sizing die and reload 'em.

I like EFW's idea better. Pull the bullets, salvage the powder, weigh a few of the charges so's you'll know how much to put back in each cartridge, and then take the decapping pin out of your resizing die and bump the necks open. Maybe a little dry mica inside and out on the neck. Be careful that you don't cycle the press all the way down lest you get a stuck case. Then recharge the case and seat your bullet. Your reformed case is gonna come up shorter but it shouldn't hurt. You'll still be doing some case forming as the 8x57 is slightly longer. I guess so it can't be loaded in the 7x57. This might make a nice winter project but I'd have to have a lot of brass before I wouldn't just buy 100 8x57 cases.

Don't do it! The shoulder on the 7mm is app. .030 further back than on the 8mm. You'll end up with en extremely dangerous excessive headspace situation.

If you try and use the brass, you'll have to open the necks up to a larger size (say 338) then run it in your 8mm dies and make a false shoulder to headspace on while you fireform the brass.

It can be done, but, to me it's not worth it when 8x57 is so readily available. Just sell the 7x57 ammo and start out with the right stuff from the start. Less headaches.

Roger

I decided a few days ago not to pursue this avenue, even though others have gotten away with it.

Thanks for all of the input. I've learned alot.

<>< Brian

I have shot a 270 round in a 7mmRM.... twice.


I must stop taking those two rifles to the range at the same time and talking others at the range that stand around my bench.

You can do lots of stuff, like using Diesel oil for pancake syrup. That does not mean you should.

I'd recommend disassembling them and neck up the brass to 8 x 57 and then reload them with the correct bullet diameter...

much safer in the long run..

Sell the 7x57, buy some 8x57, and get on with your life.

Just buy 8x57 Privi or S&B ammo. Cartridge headstamps that list a smaller diameter bullet than what is loaded are an invite to a blown up gun.

Why you would buy the incorrect ammo is a mystery.

This is very accurate, excellent brass for reloading and not the downloaded crap produced here. You want the JS (rimless) with the .323 bullet.

http://www.natchezss.com/product.cfm?contentID=productDetail&prodID=ZYV331812A&src=exrbSrch

the shoulder on a 7x57 case is set back a lil further than on a 8x57 case and Ill assure youll split the shoulders out on them if you shoot the 7x57s in a 8x57 rifle as Im a big fan of both rounds and I make all my 8x57 cases from military 30-06 cases as its relatively simple and they work perfectly.

Many [many] years ago I had a hankering for a 98 in 7x57. Put the word out and a workmates Dad had one for sale. Wasnt too flash, but had all the right bits and also had an old Japanese scope mounted, so I bought it with the intention of tidying it up to hunt with. Before I started I bought 2 boxes of ammo to see what it was capable of. Took it down the range, started shooting and no way could I get it to perform - minute of biscuit box at 25! Minute of barn door at 100! Recoil was very mild - you know where this heading eh? Gutted with the whole procedure I shot off the whole 40 rounds in desperation. Took the rifle back to work, and leaned it in the corner of the workshop.
After working for a few hours, I had a wee thought, so went through to the gun workshop and found an 8x57 round and simply tried it in the barrel as the rifle was still leaning in the corner - it fitted!
Long story short, rifle was a vey nice VZ33, 8x57. After a bit of work, some new mounts and scope I had a 6 1/4lb hunting rifle, that worked for me for several years. And the cases I used for reloading were the original 2 boxes of 7x57, not a single one was split or had case separation.