If you are going to reload you should tighten up your headspace to help prevent deforming your brass if you are reloading American made cases.

Much of what you read about "headspace issues" are caused by shooting American made SAAMI cases that have tighter headspace requirment settings.

These American SAAMI cases are not made to British and Commonwealth military specifications and are weaker and stretch and thin in the Enfield's chamber.

Below is a factory Winchester case fired in my No.4 Maltby with the headspace set at .066, the case has stretched and thinned in the web area by .009 (nine thousandths) on the first firing.

On the opposite end of the spectrum I just finished checking and prepping 500 once fired Greek HXP cases that were fired in several different machine guns and several different Enfield's, NOT ONE of these HXP cases had any thinning in the web area NONE OF THEM.

Headspace is governed by the cases you are shooting and not the specifications written in the military manuals.

Case in point, below is the Canadian No.4 headspace settings published in 2002.

I read this as:

.064 GO

.070 NO-GO

.074 FIELD

The book below tells you to set your headspace to .003 (three thousandths) over your rim thickness and it was written in 2005.

This book below tells you to set your headspace between .064 and .067 and it was written in 1946.

If I remember correctly today or currently there are five different specifications for American cartridge case brass, meaning a pistol case with a chamber pressure of 18,000 CUP is not made to the same specifications as rifle case designed for over 50,000 CUP.

Our American .303 ammunition is downloaded to less than 43,000 CUP in deference to all the older No.1 and older Enfield's still being used and fired.

Our American made brass cases were not designed to fire at .303 military chamber pressures and not designed for long fat chambers.

If you reload American made cases your best bet is to set your headspace as tight as possible as it is the only distance you can shorten, you can't make the chamber smaller in diameter.

On my No.4 Mk2 below I fitted a second bolt head and set the headspace .003 over my case rim thickness or the head space is set at slightly less than .062, with Remington cases that were reloaded and fired three times the cases have only thinned in the web area .0005 or half a thousandths of an inch.

NOTE: The rim thickness of my Remington cases are .058 and this gives me slightly less than .004 head gap clearance or .004 "air gap" between the rear of the case and the bolt face, my Winchester 94 30-30 has .0045 head gap clearance and a smaller diameter chamber and less chamber pressure (38,000 CUP). The reason I bring up the 30-30 is because I think our .303 cases are being made from the same grade/spec brass.

eb in oregon

"Uh, why?"

If you look at Mr. Parashooter extremely well written Headspace 101 at the top of the forum you will see his animated .gif image of the chamber and cartridge, if you look closely you will see an "air gap" between the bolt face and the rear of the case.

This "air gap" is called head gap clearance and is the amount the case will stretch in the web area when fired, if the case stretches too far it can become deformed or warped and this is sometimes called a banana shaped case.

When a banana shaped case is reloaded the bullets are not aligned properly with the bore and accuracy suffers. Please notice that Mr.Parashooter also kept his load just slightly below 39,000 CUP which also helps keep the brass case from deforming.

These warped cases are not hard to find even without gauges, if you get tighter groups the first time you fire your new brass cases and larger groups the second time you fire these same cases the cases may be warped.

Below is a warped banana shaped case, the base of the case is as crooked as a dogs hind leg.