What yur M305 brass measures

[Seafury]

Then you have junk micrometers.

Not to be confused with a standard micrometer it is an RCBS precision micrometer for 308 Win. Like I said it is 0.002' under actual. That's assuming the 4 Forester head space gauges I have are correct. And I've seen where others have stated it is more of a comparator than exact measurement.

 

[PitBull1973]

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.

Ok please answer if you could. I have 20 rds of factory brass once fired and the all measure 1.632 . I'm planning on using 7.62x51 brass . Should I be safe. Thanks

 

[yomomma]

Brass doesn't matter if you are reloading. You need to watch out for factory loads and especially military ammo if you have a match chamber.

 

[45ACPKING]

brass doesn't matter if you are reloading. You need to watch out for factory loads and especially military ammo if you have a match chamber.

this ^^^

 

[PitBull1973]

Ok thanks

 

[raindog]

Not to be confused with a standard micrometer it is an RCBS precision micrometer for 308 Win. Like I said it is 0.002' under actual. That's assuming the 4 Forester head space gauges I have are correct. And I've seen where others have stated it is more of a comparator than exact measurement.

Seafury has it right.

The RCBS precision micrometer is a cartridge case comparator only, and I very much doubt any two would necessarily read the same. Mine reads 0.048 on a 1.632 Forster head space gauge, and I can't imagine why people assume that it measures headspace directly. No where on the body of my micrometer can be found a 1.6 increment, but unfortunately some people assume the graduations on the thimble correspond to 1.6xx. Each graduation on the thimble corresponds to exactly .001" however, so precise comparisons are easily measured.

It is very useful for setting dies to shoulder bump cases just a thou or two under the actual chamber headspace while resizing - it is not designed to replace actual headspace gauges for chamber measurement.

 

[45ACPKING]

Seafury has it right.

The RCBS precision micrometer is a cartridge case comparator only, and I very much doubt any two would necessarily read the same. Mine reads 0.048 on a 1.632 Forester head space gauge, and I can't imagine why people assume that it measures headspace directly. No where on the body of my micrometer can be found a 1.6 increment, but unfortunately some people assume the graduations on the thimble correspond to 1.6xx. Each graduation on the thimble corresponds to exactly .001" however, so precise comparisons are easily measured.

It is very useful for setting dies to shoulder bump cases just a thou or two under the actual chamber headspace while resizing - it is not designed to replace actual headspace gauges for chamber measurement.

yes, something I've been trying to convince my fellow m14 nuts of for many years when they have come to me panicking that they were told their brass mic'd out way over desireable headspace.

 

[Seafury]

I've had some brass fired from my M1A that measured 1.630" and most cases longer when factory headspace was 1.632" . that was enough to convince me it wasn't fool proof chamber measuring method.

 

[flashman]

ya, somethins not right there. typo?
otherwise that's below chamber spec, if it even chambered a round with full lock up.... the pressures would be WAY up there -----> your #### will fall off

Yuppers... Add 10 thou to that, finger was one key to the left.

 

[yomomma]

Like I said. It was always a "rough" measurement to give you an idea of where about you chamber sits. I always figured that the brass was always a bit smaller than the chamber. If it weren't you would have a stuck case.

I've had some brass fired from my M1A that measured 1.630" and most cases longer when factory headspace was 1.632" . that was enough to convince me it wasn't fool proof chamber measuring method.

 

[buckbrush]

Forster headspace gauges are not known for their accuracy, that is why they are so cheap.

 

[Pop]

Forster headspace gauges are not known for their accuracy, that is why they are so cheap.

They're only a couple of dollars cheaper than the Clymer ones at Brownell's, but Clymer are often completely sold out for months at a time (grrr).

 

[buckbrush]

you can order directly from Clymer or Manson

 

[Seafury]

Forster headspace gauges are not known for their accuracy, that is why they are so cheap.

And yet all 4 of them measure 0.002" under their specified dimension with the RCBS mic.