I keep a homemade broken shell extractor in my range bag. Lesson happened to be learned firing 303 British too. Third firing of that piece of brass BTW.
The "o-ring" thing is great advice, but it is a PITA.
I'm kind of torn between getting all set up with brass specifically labelled and loaded for each rifle using the "o-ring" method, or just accept that 303 brass has maybe half the case life of other brass, come up with one standard load for all my rifles, and carry on like that.
I read about the o-ring method and was very skeptical of the idea and didn't try it for over six years. The old standby methods of seating your bullets long and jamming the bullet into the rifling didn't work to hold the case against the bolt face because of Cordite throat erosion. The second method of creating a false shoulder was hard on the case necks and I ended up with split necks.
The o-ring methods very well and the only downside is you MUST grease your locking lugs to prevent wear on the lugs. It is also important to not use o-rings that are too large and have excessive bolt closing effort.
The most important thing to remember is civilian American made SAAMI cartridge cases are not heavy duty military cases and are short lived if not fire formed properly. On top of this our .303 resizing dies are designed for smaller diameter and length non military chamber.
For me the Winchester case gave the shortest use and the Serbian Prvi Partizan cases gave the longest use. This is because the Prvi cases have thicker rims, the base diameter is larger and the cases were over .010 thicker in the base.
When reloading cases like Winchester you need to load lighter, meaning a 150 grain bullet and 37 to 38 grains of IMR-4895 to not over stress the weaker brass. By using the o-ring method and mid range loads I have gotten over 30 reloads from my cases.
This isn't written in stone and it depends on the type and quality of the brass and your Enfields chamber. BUT I do not blame the Enfield rifle for this, my 1943 Remington 03-A3 was almost as hard on 30-06 brass when loaded near the top because of the oversized military chamber.
Bottom line, you have a long fat chamber and skinny short reloading dies and you need to compensate for the difference.
New cases can be on the short side, below is a brand new unfired Remington .303 British case resting in a Wilson case gauge. The case rim is actually hitting the inside of the gauge and the shoulder is actually a 1/4 inch short of where it should be.
Below is South African surplus military ammunition, it is resting on its shoulder as it should be.
Below is a fired case resting in the gauge, the distance it is sticking above the gauge is how much further the shoulder location is in the military chamber. It is also why neck sizing prolongs case life in your Enfield rifles.
Now also remember this, when using the o-ring method the o-ring is compressed when the bolt is closed and centers the rear of the case in the chamber. This helps when fire forming cases with smaller base diameters and aids accuracy.
Once the case is fire formed the case no longer headspaces on the rim and the case then headspaces on the shoulder and the shoulder of the case holds the case against the bolt face and the case can not stretch.
I also want you all to know I'm an American and a smart Canadian came up with this idea using the o-ring method long ago. I just took the idea and ran with it testing it and then making illustrations showing how it was done.
All you need are some cheap .312 pistol bullets and some Trail Boss powder and a little extra time waiting for these really slow bullet to hit the target.
You do not need reduced loads to fire form your cases and you can use any bullet weight, just remember you don't need max loads to form the brass. And reduced loads are fun to shoot and cost less and you are turning your rifle into a long barreled magnum pistol.
