copyright 1999 Stephen Redgwell
Reloaders that are new to the 303 British cartridge
have to understand that their chambers are probably a little long - NOT larger in diameter. Unlike today's commercial firearms,
the chamber dimensions of most Lee Enfields vary greatly in size. It's this internal space that must be considered when reloading
for the cartridge.
IT'S MILITARY SURPLUS!!
Lee Enfields were built in many countries, during peacetime
and while at war, for over sixty years. Production methods and quality controls differed greatly. Some saw severe service
while others went virtually unused, spending years on armourer's racks or in storage containers. Is any of this really important?
Oh yes! Being aware of these variables and adjusting for them will produce tighter groups and extend case life. What makes
1. They were built for military use and not for commercial sale.
2. Many have seen war
service and have been bounced all over the world.
3. Some were well maintained and properly stored while others were
abused and ignored.
4. No thought was given to reclaiming and reloading fired cases.
5. Each rifle is a law unto
itself - more so than virtually any other firearm - commercial or not.
HEADSPACE - WHAT'S THE SCOOP?
Most modern rifle cartridges are referred to as rimless, but that's not 100 percent correct. They all have a rim - it just
doesn't extend past the wall of the case. Rimless cases use the distance measured from the bolt face to the middle of the
shoulder to determine headspace. This length or measurement is standard. It has been predetermined and accepted by the industry
as a given length.
But what about the 303 British? It's a rimmed case!
Looking at the picture above, you can see a shaded area just forward of the bolt face. This is a recessed area that houses
the rim when a cartridge is chambered. The size of this area is measured from the bolt face to the end of the recess, when
the bolt is closed. How large this area is, determines headspace. If this distance increases, your headspace is moving toward
There are two standards I know of for measuring headspace - CDN military and SAAMI/Australian.
Most gunsmiths use the tighter SAAMI gauges when accessing headspace. I said most - not all. If your rifle is assessed as
"serviceable" using military gauges, there is a distinct possibility that you will experience more case stretching.
If this is so, you might want to tighten up the headspace.
A THIRD STANDARD?? - Information provided by David Moses - Thanks!
There is one more standard for the .303 and that is the CIP norm. CIP (see explanation below) states that the max cartridge
rim thickness R is 1.63 mm; min barrel relief R is also 1.63 mm. The max allowable headspace (in the case of the CIP, this
is the air space between the max ctg R and the breech face) is 0.15 mm.
In our terminology, "go" would be 1.63 mm or 0.064"; "no go" would be 1.63 + 0.15 mm = 1.78 mm
or 0.070". This is obviously based on military specs. Naturally, there is no "field" gage for CIP proof norms.
ADJUSTING HEADSPACE FOR THE NO 4 RIFLE
If you've got a No 4 rifle, check the bolt head. On the top, there is a number stamped into the metal. The numbers go
from "0" to "3". Each increment of one adds 3 thousandths of an inch to the length of the bolt head.
If the number stamped there is 0, 1 or 2 you will be able to adjust the headspace by simply removing (unscrewing) the bolt
head and installing another with the next highest number. It will be necessary for you to check using the gauges again.
If you've got a No 1 rifle, the fix isn't as easy. Leave it with the gunsmith and let him work his magic. The bolt heads
are not interchangeable like the No 4s.
BACK TO THE CHAMBER or THIS CASE WILL GROW ON YA
So, you chamber the cartridge and lock it into place by fully closing the bolt. When you fire the cartridge, the sides,
shoulder and neck all expand outward to fit the chamber wall. They do spring back slightly, but what you have, in effect,
is a tailor made case that is unique within the world of Lee Enfields. Most people notice that the shoulder moves forward
when they hold a fired case up beside an unfired one. Remember, shoulder position is not important for headspacing rimmed
This is where many people start causing the trouble of cracks and separations. They take this marvelously formed case,
which, like a snowflake, is one of a kind, and run it through their full length die...crushing it back to its approximate,
Subsequent firing and full length resizing overworks the brass and its life is reduced. It's this complete cycle that
prematurely ends its usefulness. The solution is simple - neck resize!
To stop overworking the brass, neck resize your cases. The major benefit comes as more shots from each case. It may
also improve accuracy. Less effort is required to neck size, and it is easier and faster. Some die companies have optional
elliptical expanders, which work the brass a little less as well. Every little bit helps.
Case stretch is inevitable - so when should you full length resize? When the shoulder moves too far forward and chambering
becomes difficult. You have a couple of options. The first is to push the shoulder back by adjusting your full length die
to resize the neck and just touch or "bump" the case shoulder. Using this method will also partially reduce the
The second option is to use a special body die made by Redding. It's designed to full length resize the body and move
the shoulder back without reducing the neck. It's an inexpensive addition to your bench that will help resize cases whose
shoulders have moved forward with use.
Let's review the steps to extend the life of your brass.
LIFE EXTENSION OF 303 BRITISH CASES
1. Tighten up your headspace according to SAAMI specifications
2. Fireform cases using midrange loads
3. Neck size only
4. Use an elliptical expander in your reloading die
5. When chambering becomes difficult because of shoulder position,partial resize with a full length die or use a Redding
6. Don't use max loads unless you have to!