30 BR neckturning problem

[dunraven]

am prepping 6BR Lapua brass to be used in a 30 BR. have noticed that probably 90% of the cases are showing splits or cracks, parallel to the long axis of the case, starting at the neck/shoulder junction, and running 1-2 mm. I noticed it with the naked eye on one case and began checking them with a 10X loupe. it's only noticeable AFTER the cases have been neck-turned, so it seems to be internal.

Am I creating this by expanding the cases on a Sinclair mandrel, by going from .243 to .308 directly? Is this too great a step? I find it hard to believe all these cases are 'defective'. And, can they still be used?

 

[spclark]

I think you're expecting too much of your brass to stretch it more than 1/16" in one go. As for using cases with cracked necks that you can see... probably not a good idea.

As a test, you may want to try annealing a case neck or two prior to stretching it & see what happens, but better to get a series of gradually increasing neck expander balls made for this & go at it with the proper tooling.

I use a Sinclair expander mandrel to take 22-250 cases up to .243 for 6XC but that's less than one-third the stretch you're doing & I'm guessing the 6BR brass has thicker necks too....

 

[JoePellegrene]

Just using a .308 mandrel in one step is too much. Some guy's use the K&M mandrel it will size the case in one step, but I've never tried it. I use two different mandrels, and I also turn the necks twice.

 

[spclark]

Redding makes a tapered .243 > .308 sizing button:

http://www.redding-reloading.com/pages/sizebuttons.html

- but consider if you will how it's shaped, when compared to Sinclair's mandrels,attached, if I can get it to upload), meant for a different kind of operation.

You don't want to be pushing brass into a new diameter too fast. It'll stretch, but if you move it too fast...

 

[tenring]

I use a 264 expander before the .308; probably a .270 or .284 would also work. But - first champfer the inside case neck before you begin, and be absolutely certain the .308 expander nose fits perfectly on the case mouth inner lip before you raise the ram. Lube both surfaces well prior to each pass.

 

[tiny68]

Well I think you can do it with one past with no problems. I have made over 200 cases the Redding 6mm to 30 cal. tapper expander,NO.16307). I use Imperial Sizing Wax and I have never lose a 30BR case. I turn the necks and then anneal the brass after expanding. This may not be the most perfect way but it has served me well with my 30BR explorations. I am not a competitive shooter but I am trying to learn some ends and outs to see if I really want to make the equipment investment. Luck, tiny