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Fire Forming Question

wkdickinson

Gold $$ Contributor
I am fire forming 100 pieces of new Alpha 6 Dasher brass. The shoulders on the new cases are about .004-.005 shorter than fired cases. I am thinking I should seat the bullets to “jam” in order to give the shoulder the greatest opportunity to move forward. Is my logic correct?
 
0.004" is usually the difference between the go and no-go gauge. So 0.005" is not too bad and I wouldn't worry about it. I've had many Lapua cases that measured the same as your alpha brass and I had no problems.

However, if you'll sleep better after jamming them, then go for it. Either way, no harm done.

Once you get to about 0.007" that's where the buck stops for me.
 
I am fire forming 100 pieces of new Alpha 6 Dasher brass. The shoulders on the new cases are about .004-.005 shorter than fired cases. I am thinking I should seat the bullets to “jam” in order to give the shoulder the greatest opportunity to move forward. Is my logic correct?
I’m getting ready to do the same thing Monday and I’m going to try using Zip pistol powder and some wadded up toilet paper, no bullets. But if you were using bullets, your thought process to jam the bullets is 100% correct
 
OK ... someone has to ask ... what's the difference between "fire-form" and "shoot"? Don't you fire-form brass when you shoot it?
yes, but
people also fire form as a separate action
either with a bullet, often a lower quality bullet and a little less powder
or
WITHOUT A BULLET and a fast pistol powder some with no filler some with
some go as far to ahve a dedicated second bbl, often a used bbl chambered the same as the match rifle and fire form in it....one guy has the chmaber right but the throat and bbl in 6mm to form 30br brass with a 6mm bullet!
 
Or you could load them like your Match round's and go shoot.
I have many times been compettive and even Won with a first time firing of my brass.
If its close in your measurment's your good to go in my book. Why waste components.
 
I chambered my own 6 dasher with Alpha brass as part of the go gage process along with a regular go gauge...so I can just run the brass through a neck mandrel, then load and shoot them with my normal favorite hot load recipes...it's very accurate with the new unfired brass. Shot 13 - 5 shot groups that averaged .313" all with several different powders, charge weights, and bullets. Berger & Nosler 105,
Sierra 107, Hornady, and Berger 108, Sierra 110, Barns 112, DTAC & Nosler 115 ...
 

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