Case forming overlength?

[DonMountain]

I am in the process of forming 8x57 Mauser cases from 30-06 cases and its been several years since I have reformed cases. My question is, should I trim the cases all the way back to the "trim to" length after case forming, knowing that when fireforming the cases will shrink in length? Or should I leave them maybe 0.01 inches long and then fireform them with a reduced load and then trim them to final length? :cbpour:

[badgeredd]

I am in the process of forming 8x57 Mauser cases from 30-06 cases and its been several years since I have reformed cases. My question is, should I trim the cases all the way back to the "trim to" length after case forming, knowing that when fireforming the cases will shrink in length? Or should I leave them maybe 0.01 inches long and then fireform them with a reduced load and then trim them to final length? :cbpour:

I personally prefer to trim the new cases to a chamber cast or pounded slug. I then trim them to .010 shorter than the maximum length dictated by my chamber. After fire-forming I trim again IF necessary. For cast boolits this procedure gives me the best accuracy. One caution though, if you multiple rifles with the same chambering, be careful that you are making brass to the shortest dimension, for safety sake.

Edd

[plainsman456]

I leave them a little long before firing,then after firing trim to length.
When i tried it several ways this worked best.

[DonMountain]

So, how much longer than the book "trim to" length should I leave the cases after forming and before fireforming? Is 0.010" enough?

[geargnasher]

I do basically what BadgerEdd does, I like my brass as long as safely possible, and tend to neck-size only once it's fireformed to minimize growth. Chamber slugs/castings are the best way to tell.

I also tend to prefer .270 brass for one of my '06s because the chamber neck is a bit long on that one, but have to segregate because it would be unsafe in some of my other guns.

Gear

[runfiverun]

i keep mine as long as possible also.
the book gives you saami measurements.
your rifle gives you it's measurements.
if you aren't gonna measure the actual neck length, trim to the long side then re-measure after firing.

[1Shirt]

I am with Gear on this one!
1Shirt!

[Larry Gibson]

I also chamber cast and trim the necks to the maximum actual chamber neck length as badgeredd does. When fire formed the should blows out and the necks actually get a tudge shorter. I then NS after that for maximum case life and best accuracy.

Larry Gibson