Headspace problem...I think.

[CommandoX]

Hello all. I need some advice.

Purchased an Ishapore Enfield 2A1 (1967) from a friend and I have started load development for it. Shot it in the past and had no problems and was unaware of any.

First time out with it and shooting current (12/13date) LC brass. This brass has been picked up from the range and reloaded twice but it was only fired once before. On this second shooting of the brass, I had one cracked case on the lower body upon home inspection. Almost all the other pieces show the "ring" on the lower body as well. I did a bunch of reading on this as it was the first time I'd seen it on any cases I've used.

I believe I've ruled out overpressure/hot loads as I was using the minimum recommended loads or lower. IE: per Hodgdon magazine 41.5gr of IMR 4064. That load showed flattened primers but nothing else and had a speed of about 2650 with 168gr Hornady Match HPBT . I also had 40.0 gr and 40.5 gr loads that I fired that showed less primer flattening with the same bullet and appropriate speeds. All rounds were loaded to 2.800 inches COAL.

Later at home I pulled out my headspace gages and found that the cases measured 1.646". Not having enough experience with this, I tried to reproduce this measurement with my die. I was not able to set it up to get to that number. The most I was able to reach was about 1.634".

Is this gun's headspace toasted or am I missing something?

[Bart B.]

I suggest you set your sizing die about 1/7th turn up, lock it in place then size another fired case. Measure its headspsce and let us know what it is.

[Snyper]

Headspace for a 7.62 X 51 NATO is 1.645

Headspace for a 308 Win is 1.632

I suspect your dies are for a 308 and your chamber is cut for a 7.62

http://www.thegunzone.com/images/762v308.jpg

You can try just neck sizing after the initial firing in your gun

A bright line on the outside of the case just shows where the die stopped, and isn't unusual

Use a piece of small stiff wire or a dental pick type tool with a short 90 degree bend on the end to feel the INSIDE of the case wall near the bottom to check for any groove, which would indicate the case has stretched and is much thinner there

[Bart B.]

According to MIL-SPECS, 7.62 NATO chamber headspace shall be a maximum of 1.640 inches and a minimum of 1.630 inches. Best perfromance and accuracy has been when it's near minimum. The US 7.62 NATO service rifles headspace I've measured have been between 1.630 and 1.633 inches.

In contrast, SAAMI specs for .308 Win. chamber headspace is 1.630 to 1.634 inch.

[CommandoX]

I thank you for the info. guys. Sadly, I was unaware of the .01 difference in regular vs Nato brass. Now I know.

I'm going to start this process over again with already measured, once fired and neck sized from this gun brass.

I'm also sizing some once fired (range) cbc nato brass to 1.630/.631 and I'll try that out as well.

I'll report back when I have more info.

[Bart B.]

That .01" difference is for chamber headspace, not case headspace. SAAMI specs for case headspace is 1.627" to 1.634". The NATO case headspace is 1.628" to 1.634". 98% plus of both types of new cases I've measured have been between 1.627" and 1.630".

If the fired cases have headspace at about 1.646", I recommend sizing them to no less than 1.643". Otherwise, case head separation may happen in only two reloads on a case. And accuracy will not be too good, either.

About .003" difference between chamber and case headspace is best for both safety and accuracy in semiautos; .001" to .002" for bolt guns. Any more and the case body will stretch too much at the head when fired.

[CommandoX]

Ah!

Ok Bart. I got it now. Thank you.

I'll update as I move forward.

[mehavey]

If the fired cases have headspace at about 1.646",
I recommend sizing them to no less than 1.643".

^^^^ This.

As a shooter of minimum SAAMI-spec (1.627") headspaced cases
found in commercial ammo, you have a headspace problem.**

As a reloader, you don't.








** Page 66:
http://saami.org/specifications_and_...wnload/206.pdf

[Bart B.]

You might consider getting a 308 Win GO headspsce gauge then measure it with the same tool used on cases. It should read 1.630" but if not, you'll need to adjust the readings on cases by the difference. If it reads 1.636", you have to subtract .006" from case readings to get real world numbers.

This issue is common with Hornady's LNL gauge.

[PA-Joe]

During war time production exact headspacing wasn't a concern. You may have a very long headspace.

Back you sizing die out two turn and is if it feeds into your chamber. If not turn the die in 1/4 turn at a time until the case fits your chamber.

You can also measure the headspace on a fired round and then set your die to that measurement. You should not set the shoulder back more than 0.001 inches.

[Bart B.]

As the OP's die sizes cases about .010" too short in headspace, I don't think moving the die up 2 turns (or .143") is a good idea for a starting point. No more than .014" to start and that's about 1/5th turn. !/4 turns moves the die .018" which is too much for fine adjustments to get proper case headspace.

Using these die labels will help one adust their sizing dies very accurately:

http://s860.photobucket.com/user/jep...ent-1.jpg.html

so they'll look like this when the .002" label's used:



If you set a sizing die to just stop its shoulder on a headspace gauge set in the shellholder, it' won't size to the gauge's headspace dimension.