300BlkTalk

I have been reloading for about a year now, no problems, yet.
All my questions have been explained and I think, I'm doing ok.
However, I was recently, reloading some 308 and decided, on a whim, to check headspace.
Well, that may have been a mistake, here is my quandry...
Saami spec says min headspace for 308 is 1.630, max 1.640.
My fire formed brass is measuring 1.6275.
When I full length resize, my headspace measures 1.6240.
These readings are with the Hornady comparator with the 400 insert.
Saami says the datum line for 308 is measured at .400 and my 400 insert is sized at .400, so, I think I am measuring properly.

So, am I mis-sizing my brass, should I readjust my sizing die, or am I chasing unicorns and am thinking too much?
I have had no issues in loading, firing, or extracting rounds, and my accuracy is sub moa.
I should say my die was set-up as instructed, just touching raised shell holder, then 1/4 turn extra, and locked down.

Any thoughts and/or suggestions would be greatly appreciated.

if your reloads chamber successfully, and evertyhing else is ok... other than fired brass measurement... i wouldnt sweat it toooooo much.



one thing that may help is knowing what kind of firearm you're working with - like a bolt gun/msr/etc.

The rifle is a Rem 700.
So, yeah, I know the bolt action will be more "forgiving".

Headspace a bit tight is not going to be a problem, too loose is. As long as they chamber, fire and extract OK, without signs of pressure, then you should be fine.

You could loosen the sizing die enough to get your brass to size to the minimum spec but I would not if you are getting the accuracy you say.

What I do is measure a few of my fired cases, average the results and then size to about .002 less than the average. Before I had the headspace gauge, I would size my brass a little at a time until it chambered, then push the neck down a smidge more. With the gauge, I write down my measurements for all my rifles to keep track of any changes, and to reset my dies in case I have to take them off the turret for some reason.

First, the tool will not give an accurate measure of the base to datum line.

The bore size of the insert is .400", but the opening has a slight radius or chamfer, so it will be very slightly larger. Your measurement will be short.

Unless the brass was fired multiple times or a pretty hot load, it will not be done growing, so it's not a true representation of the chamber length.

A comparator is not really a measuring tool, it is a comparing tool. You compared the brass before and after sizing and found you moved the shoulder .0035". Sounds like you used it right.

I would back off the die 1/2 turn, size a fired case measure, and see if it chambers. If it chambers, then load and shoot a few and measure them again. My guess is they will be a bit longer than 1.6275".

I won't decide on a die setting until the shoulder quits changing length.

What do you call a 308 Win No-Go that just fits ... ... ... 7.62 NATO.

Sorry, I couldn't resist.

I'm pretty sure I could close all my 308 Win bolts on a 308 Win No-Go if I really tried. A lot of long is bad, but a little long or close to long is just versatile in 308.