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I've been loading .308 successfully for years using a Redding full length sizing die and competition shellholders.

I clean the die occasionally with Pro-Shot copper solvent as it gets a build up of brass which scratches the case necks.

This may be irrelevant to the problem, but on the last clean I left the solvent in for a few days by mistake.

Anyway, of all the rounds I've loaded since then approximately half will not chamber due to insufficient headspace.

Any ideas what could be causing this inconsistency?

If the only thing that has changed is the solvent left in the die it could be the caustic solvent has dried out and corroded the inside of the die.....what does the inside of the die look like now?

Have you changed the cases at all?
Do you use a sizer with a neck expander?

snayperskaya wrote:If the only thing that has changed is the solvent left in the die it could be the caustic solvent has dried out and corroded the inside of the die.....what does the inside of the die look like now?

I inspected it with my borescope. It looks fine to me.

Mattnall wrote:Have you changed the cases at all?
Do you use a sizer with a neck expander?

I only use Lapua cases. I size without an exander ball then use a mandrel.

Racalman wrote:
I only use Lapua cases. I size without an exander ball then use a mandrel.

Well that answers that then.
Are they new cases or previously fired?
Seems like you may have to readjust your dies to suit the new conditions, whatever the cause.

Mattnall wrote:

Racalman wrote:
I only use Lapua cases. I size without an exander ball then use a mandrel.

Well that answers that then.
Are they new cases or previously fired?
Seems like you may have to readjust your dies to suit the new conditions, whatever the cause.

Previously fired. I've tried using different thicknesses of shellholder but I'm not getting consistent results. Some cases are in spec and some won't chamber. I normally aim for 1.628" headspace but some cases come out nearly 10 thou higher.

I may just give up and buy a new die. I've had this one for 20 years.

What about the case length? Are some cases longer than others or are they all about the same length give or take a few thou?

At what point do they not chamber? Do you only feel resistance when you rotate the bolt handle or do you feel the resistance whilst feeding the case into the chamber?

Racalman wrote:approximately half will not chamber due to insufficient headspace.

By how much does the case head-to-shoulder-datum measurement exceed the equivalent chamber dimension?
A couple of thousandths too long is barely noticable until you remove the firing pin. It takes a significant overlap to be un-chamberable.

If some chamber and some do not (and the problem is headspace as you suggest), what is the range of case head-to-shoulder-datum measurements you are seeing? Is this more than usual?

..

Racalman wrote:I've been loading .308 successfully for years using a Redding full length sizing die and competition shellholders.

I clean the die occasionally with Pro-Shot copper solvent as it gets a build up of brass which scratches the case necks.

This may be irrelevant to the problem, but on the last clean I left the solvent in for a few days by mistake.

Anyway, of all the rounds I've loaded since then approximately half will not chamber due to insufficient headspace.

Any ideas what could be causing this inconsistency?

Mattinall - headspace is measured from the SHOULDER of the chamber to the BOLTFACE. If you think you have a headspace problem - easy check - try and chamber a BRAND NEW UNSIZED UNFIRED LAPUA case. I guarantee it will chamber.

So, if it does, the problem is not headspace.