fire forming brass

[greyspider56]

I'm a little confused about fire forming your brass. I understand the process but if you full size your fired brass, doesn't that negate the point of forming to the chamber?

Thanks
Mike

 

[Bill Norris]

I'm a little confused about fire forming your brass. I understand the process but if you full size your fired brass, doesn't that negate the point of forming to the chamber?

Thanks
Mike

Not by just bumping the shoulders back a couple thousandths. A dollar bill is .004 thick so in comparison .002 is not moving the brass very much at all. And the idea is simply just that. Size it just enough to make it chamber smoothly.

 

[greyspider56]

Not by just bumping the shoulders back a couple thousandths. A dollar bill is .004 thick so in comparison .002 is not moving the brass very much at all. And the idea is simply just that. Size it just enough to make it chamber smoothly.

thank you

 

[Bill Norris]

U bet.

 

[jackieschmidt]

If you look at any new unfired case, it will exhibit somewhat more body taper than a case that has been fired.

Most full length dies do not size the case down to that original configuration.

So, to get the tune right, you need to gain the volume and consistency of a fired case.

years ago, just about every “expert” on Rifles stated that for optimum accuracy, a shooter should avoid full length sizing, since in theory the case that fit your chamber perfectly would be the most accurate.

I would venture a guess that 99.99% of all accuracy minded shooters in every center fire discipline full length size.

 

[jepp2]

Not by just bumping the shoulders back a couple thousandths.

And I take that even further. Understand that after a single firing, your brass case head to datum length may be several thousandths shorter than your chamber headspace. So for all my rifles the numbers I record are:
1 case head to datum length where I can feel a stripped bolt close on the brass
2 case head to datum length of my new brass
3 case head to datum length for brass fired in my rifle

Much of them time I FL size and do not bump the shoulder back any. If the fired round is already shorter than 1, I just size so the shoulder is in the same position. As you size, the shoulder actually moves forward (longer) as the die squeezes the case body to reduce the diameter. So I just set the shoulder where it was after firing.

 

[Straightshooter1]

I'm a little confused about fire forming your brass. I understand the process but if you full size your fired brass, doesn't that negate the point of forming to the chamber?

Thanks
Mike

Until you fireform your brass, you can't really set up your die to size cases properly using virgin brass as they can have substantially different dimensions than one's chamber. Once you've got the the brass fireformed and your sizing die adjusted according to them. Then you can get consistent sizing since all the brass will have the same starting point letting the die work on them consistently (consistently as possible anyway, given variations within each piece of brass, like their thicknesses).