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jason75979 · May 21, 2012, 08:43 PM

I recently had a local 'smith assemble a rifle for me with my chosen parts. The action is an FN SPR, the barrel a Shilen match grade stainless select blank which he turned and chambered in .308 for me.
I purchased 2 boxes of ammo to break it in and begin the process of tuning a load for the rifle with the spent brass. I've read before how one member is adamant about checking the length of an unfired round before firing to provide a "measurement" if you will, of the effect the chamber has upon the casing. Well, the measurements were all over the place. From 1.623 to 1.64 prior to firing checked with a Hornady headspace comparator gauge.
After the firing, the brass is, for the most part, shorter

But, all fall within .0005 of each other(1.624-1.6235(guessing at the .0005 as its halfway at least between the 3 and 4)).
My question is wouldn't the firing "stretch" the cases to form the chamber dimensions? And if too small(the chambers headspace) wouldn't there be indications of excessive pressure?

May 21, 2012, 08:43 PM	#1
jason75979 Senior Member Join Date: February 1, 2009 Location: Southeast Texas Posts: 137	Headspace question I recently had a local 'smith assemble a rifle for me with my chosen parts. The action is an FN SPR, the barrel a Shilen match grade stainless select blank which he turned and chambered in .308 for me. I purchased 2 boxes of ammo to break it in and begin the process of tuning a load for the rifle with the spent brass. I've read before how one member is adamant about checking the length of an unfired round before firing to provide a "measurement" if you will, of the effect the chamber has upon the casing. Well, the measurements were all over the place. From 1.623 to 1.64 prior to firing checked with a Hornady headspace comparator gauge. After the firing, the brass is, for the most part, shorter But, all fall within .0005 of each other(1.624-1.6235(guessing at the .0005 as its halfway at least between the 3 and 4)). My question is wouldn't the firing "stretch" the cases to form the chamber dimensions? And if too small(the chambers headspace) wouldn't there be indications of excessive pressure?