Forming 6mm AI from 8x57 Mauser
 

So a little back story. I’ve been playing around with a semi custom 6mm AI I had built several years ago. I didn’t even get to really shooting the thing for probably two years after completion. Shameful. I know.

Anywho, I’ve been primarily using Remington brass to fire form and I’m nearing the end of my rope on trying to make it work and last. It just isn’t very good stuff for such application. The small quantity of Norma 6mm I acquired was really good but good luck finding it. I got my hands on a limited quantity of Norma 7x57 brass and formed it all down to 6mm and fire formed. It’s proved to be very good. I’m having some difficulty finding more new product but I have located a decent quantity of Lapua 8x57 and thought it might be worthwhile going through the process of making what I need out of it.

I was thinking I could go through my established process using 7x57 but add in one extra step being to neck down 8mm to 7mm before hitting it with a FL 243 Win die with no expander. Then a FL 6mm with no expander sizing down until I get the crush fit required when chambering in the rifle for proper head space. I have skipped the 243 portion before but sizing required a lot more effort than giving the cases that little 20 degree taper to start the 6mm portion. Expand up for neck turning after that. This chamber is a standard 0.276” neck so with the turning, I can essentially end up with case necks turned down just enough to replicate having a no turn neck type dimension. Not to mention much better brass quality. I’m using a bushing die for sizing my fire formed cases so changing up neck thickness on brass can be easily compensated for with a bushing swap.

Anyway, just thought I’d put out a feeler for feed back before I dropped the cake on the brass. I can’t say how much I like this cartridge but for anyone considering; to have good brass, I really don’t know if I’d do this one again when the barrel is toast.

Couple thing that may help with forming 6 mm rem brass. Seat bullets hard into the lands and lightly oil cases before shooting

Hello. Been there and done that Sir. I’ve found I preferred forming false shoulders. I never have tried them in conjunction though. Fire forming isn’t my beef. Just not happy with available brass quality.

Using 8x57 brass should work fine . I would anneal and check neck thicknesses

Many years ago a built a 17 BR and the only brass was 7 BR , that took a lot of forming !

Excellent. I can imagine that’s a process alright for the BR proposition.

you may want to size to 25 cal in the mix

You figure? Suppose it is a large enough step down to probably warrant. I have all the dies to neck down by caliber. Just a matter of cycling them through should I go that way. If it’s a better way to go I’m all ears.

Have you tried Winchester brass?

I second the suggestion to use Winchester 6 mm brass. It last quite a bit better than Rem and is so much cheaper than Norma that any life difference would never pay off. Other choice is you may want to try Lapua 8x57 brass. It is a LOT cheaper than Norma and at least as good if not better quality. Also, Privi makes excellent 7x57 brass and most of their brass is very good for a reasonable price. It is one of my favorites for reloading.

Hey Dean. Thanks for the input. And in response to DH as well. I did pick up some 6mm Winchester brass to try but haven’t loaded it up as of yet to give a run. The 8x57 brass that I found is Lapua and what I was inquiring about sizing down. Very reasonable cost, I would absolutely agree. Lapua has proven to be exceptional product and yes, quite a bit more economical than Norma. I’ve done enough fiddle f’ing with the other stuff and not getting the life in cases that barrel life is starting to enter the radar. Need to just settle on a course of action and be done with it. I could fire form with COW yes and I know lots of guys do it. I’m just not a fan. I’ve heard good things about Prvi as you say but I’ve never used it in anything other than my 22 Hornets. It is showing exceptional life in that cartridge. I never even gave it consideration in 7x57 to be honest. Will look into that a bit more. Thank you for the tip.

BL


I am definitely not a Norma brass fan. It is where Nosler and Weatherby get their brass but for the price they charge it just ins't all that good. If you want 20 or so 7x57 Privi to give them a try before springing for bags of 100 let me know. I think I could probably spare that many.

Higginson had a big pile of it last year for 35$/50. It is pretty decent stuff. I use the straight 6mm Rem in a 274 neck. Helps keep the neck cracking down since I don’t anneal.

That’s a pretty solid price point. Guess I best load up 10 or 20 and start running it through to see how it compares. I definitely can’t see it being any worse than the Rem brass.