new brass(fireforming)

[foxshot]

I was advised to use new brass rather than once fired brass for fireforming to get the best results,i already have a couple of hundred once fired lapua brass cases,any advice out there

[Vermincinerator]

I have a rule for myself, "new rifle, new brass", however if i am fireforming to an improved chamber cut in the original barrel the above may not necessarily apply.

Even with full length re-sizing it still may not be possible to chamber one lot of brass into a rifle of the same calibre

I found this when i sold a Ruger VT in 22-250 and bought a Win Mod 70 varmint in the same calibre.

No matter how much i tried, even using different FL dies, i could not re-size the cases fired in the Ruger enough to chamber in the Winchester, the problem was the web just in front of the extracter groove.

It was not swaged down by the FL die, maybe the current crop of "small base dies" may help but if you are going to that expense, you may as well buy new brass.

Having said that if your brass is sized satisfactorily and chambers easily, it will do just fine.

 

Ian

[Guest 308Panther]

Maybe I am confusing the terms here....

 

If using new brass to load and it has then been loaded and fired,it would be once fired....

but it also has been fire formed to the chamber of the rifle it was fired from.

hence the problem Vermincinarator described when loads from the Ruger were used in

his Win...

 

In the case of an Improved version,fire forming would stretch out the (base line or standard) case to

match the shoulder area of the (new)Improved chamber...you are using the combustion to

blowout (if you will) the casing...from what I have seen of "Improved" calibers it is mainly

the shoulder angle and overall length of the casing thats been improved apon.

 

I wouldnt think it would matter if you used once fired or new brass....because in either,

isnt one of the steps of the process that you anneal (soften by heat) the brass first??

From what I ve read and remember many advise annealing new cases anyway to remove any

"work hardening" from the forming of the new case.Again this would be in the need of going

from a standard caliber to an "Improved"caliber...

 

308Panther

[Vermincinerator]

Hi 308,

When fireforming a parent case in an improved chamber the case does not actually stretch if the chamber has been cut correctly, it re-forms, this is because the headspace is usually about .004" shorter then the standard chamber.

The neck/shoulder juncture of both the parent case and the improved case look to be in the same place but you will find that the improved case neck is shorter overall.

 

The almost parrallel and more acute neck angle of the improved chamber needs to be filled out by the parent case, the extra brass to do this can only come from the case overall length, as the case sides and shoulder expand to fit the chamber, the neck is actually pulled back toward the base resulting in a shorter case.

My 243 AI cases where up to .018"shorter then the parent case, they were all trimmed to give a uniform .020" shorter case

 

http://www.6mmbr.com/cartridgediagrams.html#243WIN

 

http://www.6mmbr.com/cartridgediagrams.html#243AI

 

 

So far i have found new brass soft enough to fireform in an improved chamber without having to resort to any kind of annealing.

 

Ian.

[foxshot]

The fireforming will indeed be in a new barrel using 223 lapua brass usd in my old remi 223 barrel and fireforming to 223 ackley improved any change on your thoughts all this advice is greatfuly received,if i remember rightly the advice given was that new brass was softer than once fired resulting in easier formed brass

[6mmBR]

If you find they are splitting on fireforming to Ackley, you can always anneal the once fired brass.

I doubt you will have much problem with the once fired Lapua brass though.

Cheers

Dave