.308 headspace issue? Need some advice.

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freedomintheskies

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I tried to search the forum on this but did not find what I was looking for.

Here is the situation. My F-Class gun was re-barreled last fall. It came back with less throat than I really wanted but such is life. In working up loads for it, I have experienced 2 incipient case/head failures in just over 100 rounds. The first was a Federal case that got mixed in with my Lapua. I figured it was a random anomaly. The second was yesterday with a Lapua case. I stopped shooting immediately.
Here are the details so far. Since I don't have headspace gauges, I used a full length sized case and made a foil "crush washer" on the head of the case. I chambered it and after removing it I found that I had .010" clearance between the bolt face and the case head (I used a fired but unsized case to compare length). Does this seem excessive?

Anyways, I'm going to order some new brass and just neck size from now on I think.
 
You don't measure headspace with cases... you are measuring the case head clearance which sounds excessive... make your cases so an empty brass causes the bolt to close firmly, not easily. You may have to make a false shoulder and then size to get this right. Brass made this way and then fired forms into the strongest brass...

A shorter throat is often preferable to a long throat...
 
Yes, I agree that I'm measuring the clearance. That is why I measured a fired and unsized case placed neck first into a 9mm socket and then measured for OAL. then I did the thing with the foil on a full length sized case and measured it the same way in order to establish the net difference between fired and full length sized dimensions as they exist inside the chamber of the rifle.
 
If you are the guy I saw Saturday morning with a case head separation at 600, send me a pm.
I have a gauge and would make time to get you shooting. I would think your sizing is excessive causing the trouble - easy fix.
I don't know who installed your barrel but it is unlikely that is the problem.

Cheers,
Rob
 
Use a body die set to 2 thou shorter then your headspace... Problem all gone. Lee collet neck die or bushing neck die for sizing the neck

You are oversizing your brass and assuming a random FL die should work. Dies vary dimensionally ....

Jerry
 
Mystic Precision said:
Use a body die set to 2 thou shorter then your headspace... Problem all gone. Lee collet neck die or bushing neck die for sizing the neck

You are oversizing your brass and assuming a random FL die should work. Dies vary dimensionally ....

Jerry
Click to expand...

Jerry,
This problem is a new one since I had my barrel changed. I was using the Redding competition dies all last year with great results. The brass was "experienced" through and had not been fired from my gun until this happened. I have since weeded out a bunch that was showing signs of distress.

In 20 years of reloading, this is the first time I have experienced this problem. Perhaps just neck sizing is the way to go but I thought target rifles had tighter chambers that would not work the brass too much.
 
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freedomintheskies said:
In 20 years of reloading, this is the first time I have experienced this problem. Perhaps just neck sizing is the way to go but I thought target rifles had tighter chambers that would not work the brass too much.
Click to expand...

Unless the reamer used for this barrel was the same reamer used to do the first barrel, it is common to have problems with the previously used brass.

I always recommend new brass for a new chamber.

Target rifles do not necessarily have tighter chambers but many target shooters will own their chambering reamer so they can duplicate the next re barrel and keep on using the same brass and die set up...

Neck sizing (requires a neck sizing die, not a backed off FL die) isn't as important as not pushing the shoulder back excessively on sizing.
 
freedomintheskies said:
Jerry,
This problem is a new one since I had my barrel changed. I was using the Redding competition dies all last year with great results. The brass was "experienced" through and had not been fired from my gun until this happened. I have since weeded out a bunch that was showing signs of distress.

In 20 years of reloading, this is the first time I have experienced this problem. Perhaps just neck sizing is the way to go but I thought target rifles had tighter chambers that would not work the brass too much.
Click to expand...

Assume nothing, measure everything... unless you control your reamer, you are guessing on what might be used. If a shooting sport limits to certain chambers, then those dimensions will be heavily regulated. If the part of an 'Open' class, there can be some very interesting versions of common options.

I too believe, new barrel, new brass especially with something like a 308 with very long bore life. Brass can only be fired so many times... brass work hardens and really doesn't want to reform after it have been fired in a rifle more then a few times.

But the solution I described is likely what you are experiencing. now knowing the brass is old, I would really want to size as little as possible to fit this new chamber. Work hardened cases are the most vulnerable to separation if the headspace is reduced too much.

Given your current investment, new brass isn't a big cost over the lifespan of that barrel.

Good luck.

Jerry
 
Unless you can tell me what the headspace measurement is on a piece of fl sized brass, I can't tell whether or not your issue is caused by a chamber which is cut too deep or a fl sizing die which is too short. Which ever it is, the end result of mixing the two will be the same. If a person wants to use a fl sized case as a headspace gauge, he should send one to the gunsmith who is doing the barrel work with instructions to that effect. This may result in a chamber which is non.standard, however, so the customer has to be aware of this potential. Try your foil gauge on a piece of new, unfired brass and see what you get. I would expect to see .006" or less but, due to variations in brass, you could easily see more. It's often best to match headspace to the original barrel but if the original barrel is too far off-spec, a gunsmith might be reluctant to do so. Even with proper gauges, there are variations in the gauges and reamers which can create differences in the ultimate chamber depth.
The bottom line? You can either buy new brass or have the barrel set-back. If the headspace is truly excessive (as measured with a gauge, not with a piece of fl-sized brass), I would expect any remedial work to be done as a warranty repair. If not, I would expect to pay. The personality and business practices of the shop will, of course, enter into this.
 
I received the Hornady headspace gauges yesterday and although it does not measure the actual chamber, my fired brass was .0015" over the minimum spec for a .308 chamber, so I guess it was just the brass that was worn out.
I also received 3 boxes of new Lapua brass yesterday so there should be no more surprises.
Thanks all for your replies and help.
Cheerz!
 
If your fired brass is .015" over the minimum specs for the chamber, this is not because your brass is "worn out". If you shoot that new Lapua brass in that rifle, it will also be .015" over and, if you fl size it according to most manufacturer's instructions, it will be well on it's way to separating.
 
oops! my mistake. I misread. I would check the headsdpace on a sized case though and adjust accordingly. If you have four or five thou of clearance, you will get separations in very few firings.
 
I have an RCBS precision mic cartridge headspace tool in 308W. If you want to send me a recently fired unsized case .... I can measure it as well... although doesnt really do anything that your Hornady setup cant do. Just another data point is all.

As indicated above ... even if your chamber is a little 'improved' ... as long as you resize to accomodate the new dimension -- your brass should be ok .... unless of course your loads are excessive for your set-up
 
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