What yur M305 brass measures
- Thread starter eaglesnester
- Start date
My rifles chambers measure 1.630" to 1.634" depending which one I'm shooting that day.
Now, how much does the ejected brass, fired in semi auto mode measure?
That's a tough question , depends what ammo I'm shooting , in what rifle and depends if it surplus steel case or actual brass.
Either way, I've never found the mic'ing of fired brass to be of any real use or indication of what my chamber measures. That especially goes for brass fired with the Gas On.
Now, how much does the ejected brass, fired in semi auto mode measure?
That's a tough question , depends what ammo I'm shooting , in what rifle and depends if it surplus steel case or actual brass.
Either way, I've never found the mic'ing of fired brass to be of any real use or indication of what my chamber measures. That especially goes for brass fired with the Gas On.
Lexthedestroyer
CGN frequent flyer
- Location
- Abbotsford, BC
From Barney: 16, 16, 16 thou. Although, this was before I re-indexed my barrel at a clinic last year. Should be slightly LESS, as I screwed it in 1/16-1/8 of a turn.
Edit: Didn't fully read first post (haven't had my coffee yet...) this was with gas OFF.
Edit: Didn't fully read first post (haven't had my coffee yet...) this was with gas OFF.
What does it tell you? I would say the only thing it could tell you is to seek a proffesional to measure it when the number is too large for your peace of mind.
I did not like being 14 thou over .308 go gauge(1.644) so I replaced the bolt. Too much stretch to reload.
I did not like being 14 thou over .308 go gauge(1.644) so I replaced the bolt. Too much stretch to reload.
ya, I don't put any merit in the mic'ing the brass method for measuring headspace.
when guys say their brass measures 14thou and 16thou over........ I'm assuming that works out to 1.644 to 1.646" ....... which doesn't jive with me.
I've taken a rifle, in which the owner fired 5 rounds of commercial federal 150 gr powershock , with the gas off. sent those cases off to have them measured and the results were 12 and 13thou over .308 (1.630) . I dropped in a US Military Field No go gauge (1.644) and bolt would not close, I then dropped in a US military 7.62 Nato Go gauge(1.635) and again the bolt would not close but almost. installed a Clymer 1.634 gauge and lo and behold, full lockup with a bit of drag on the gauge.
the headspace gauges showed the rifles's true headspace to be approx. 1.634" or Match NATO that's 8 or 9thou tighter than the precision mic showed.
there is a 2 thou difference in the datum measurement between .308 and 7.62nato but that would not account for the margin of difference between the mic and the headspace gauges.
after getting the results of the mic'd brass back from the guy who measured it........ the rifle's owner was hell bent on replacing the bolt on his "POS norinco" LOL
when in fact no such parts swap was needed and I put the fella's mind at ease ...... and saved him an expensive bolt swap he thought he needed.
I find it simplest to explain it all like this
any m14 type rifle with a MINIMUM headspace of 1.630" (.308 go) to a MAXIMUM of 1.640" , "should" be safe for using most commercial .308 offerings (max 174gr)
any m14 type rifle with a MINIMUM headspace of 1.6345"(7.62Nato Match) to MAXIMUM of 1.644" , "should be safe for using "real" 7.62 nato ammunition. a prime example of this ammo would be the Hirtenberger 7.62 currently being offered at marstar.
**** a caution. Many of us have built up custom rifles or had others build for us and many of those rifles have headsoace measurements of 1.630" or Match .308
I'd be real cautious using real 7.62 nato ammunition in these tight chambers. Stateside, most well known m14 types have commented that 1.632" would be a safe starting point. (for using 7.62 x 51 brass cased match ammo)
maybe it's all worrying about nothing but it would pay to know , especially if you have a rifle with a tight match chamber.
any m14 type rifle with a MINIMUM headspace of 1.630" (.308 go) to a MAXIMUM of 1.640" , "should" be safe for using most commercial .308 offerings (max 174gr)
any m14 type rifle with a MINIMUM headspace of 1.6345"(7.62Nato Match) to MAXIMUM of 1.644" , "should be safe for using "real" 7.62 nato ammunition. a prime example of this ammo would be the Hirtenberger 7.62 currently being offered at marstar.
**** a caution. Many of us have built up custom rifles or had others build for us and many of those rifles have headsoace measurements of 1.630" or Match .308
I'd be real cautious using real 7.62 nato ammunition in these tight chambers. Stateside, most well known m14 types have commented that 1.632" would be a safe starting point. (for using 7.62 x 51 brass cased match ammo)
maybe it's all worrying about nothing but it would pay to know , especially if you have a rifle with a tight match chamber.
Yup and I have actually modified my dies to size my brass a few thou smaller.
I actually measured several manufacturers rounds and only found 1 ,S&B, to be consistently below 1.630. Some manufacturers were as much as 5 thou on the plus side. Something to keep in mind when buying ammo for tight chambered M14/M305s
I actually measured several manufacturers rounds and only found 1 ,S&B, to be consistently below 1.630. Some manufacturers were as much as 5 thou on the plus side. Something to keep in mind when buying ammo for tight chambered M14/M305s
for those guys that don't want to invest in all the stuff needed to measure your chamber ect.....
there is a simple way to know if a particular ammunition is gonna work in your rifle as far as chambering safely goes.
I don't really recommend doing this anywhere else other than somewhere it is safe and legal to discharge your rifle.
strip the rifle down by removing trigger, stock, oprod and spring/guide rod
strip the bolt, remove all it's guts.
completely clean and degrease receiver lug recess and raceways. degrease bolt
ensure chamber is clean
insert live round of the prospect ammunition and close the stripped bolt.
if the bolt will not close all the way into full lockup easily , if it drags at final lockup or feels tight in any way..... it may be one to set aside for another rifle.
if it closes perfect no wiggle to a bit of wiggle room..... all is good
if yer bolt is slopping back and forth, insert a feeler gauge behind right bolt lug at full lock up. if you can slide a 10 thou or over gauge in there...... I'd also set that ammunition aside for another rifle hehehe
confusing ya yet?
there is a simple way to know if a particular ammunition is gonna work in your rifle as far as chambering safely goes.
I don't really recommend doing this anywhere else other than somewhere it is safe and legal to discharge your rifle.
strip the rifle down by removing trigger, stock, oprod and spring/guide rod
strip the bolt, remove all it's guts.
completely clean and degrease receiver lug recess and raceways. degrease bolt
ensure chamber is clean
insert live round of the prospect ammunition and close the stripped bolt.
if the bolt will not close all the way into full lockup easily , if it drags at final lockup or feels tight in any way..... it may be one to set aside for another rifle.
if it closes perfect no wiggle to a bit of wiggle room..... all is good
if yer bolt is slopping back and forth, insert a feeler gauge behind right bolt lug at full lock up. if you can slide a 10 thou or over gauge in there...... I'd also set that ammunition aside for another rifle hehehe
confusing ya yet?
The precision micrometer's are not perfectly accurate or at least mine isn't. It measures all of my head space gauges at 0.002" under what they actually are. It is useful keeping that in mind and by adding a shim I can correct that error. I find that measuring fired brass my numbers wander a bit.
