If you shoot and reload for a .303 chambered rifle you probably know all about case head separation. This is where the case stretches and thins just in front of the rim and eventually fails leaving a cartridge case minus the rim stuck in the chamber. The good news is the remains of the case is usually easily removed, either with a phosphor bronze brush or a broken case extractor. I have used both methods in the past however if you can avoid the issue in the first place life is a lot easier.
Today was a bit of change of plan and saw us at the range complete with the Lurcher at midday, the Labrador being otherwise indisposed leaping around picking up Pheasants and Partridges. The Lurcher is always happy to get out to the range as it means he can meet and greet people, run around like a, well like a Lurcher and once tired he spends some quality time sleeping in the back of the Landrover whilst we shoot, talk and generally enjoy ourselves. It works well for all parties concerned.
As this was a bit of a last minute thing we opted to take four rifles. The Schmidt Rubin M1911 chambered in 7,5×55 Swiss. A BSA Lee Speed (Sporter) chambered in .303 British along with a BSA No1 Mk3 Sporter, again in .303 British and finally the Savage M1899 chambered in 22 Savage High Power. The middle two rifles being .303 were in dire need of some new brass and this gave me the opportunity to show you how I fire form my .303 Brass.
The vast majority of people load their favourite .303 round typically with around 41,0 grains of N140 behind a 174 grain SMK which works well for distance stuff and is a reasonable approximation of MkVII Ball. Get it right and you have a superbly accurate round. Incidentally, I usually start at around 39,0 grains of N140 and work up, I have also found similar loads with RS50 (What was TR140) work equally well although RS50 appears to fractionally slower than N140 which is not a bad thing. Whatever you opt for please do ensure it is safe for you rifle.
Once loaded it is simply a matter of stuffing the round in your rifle and pulling the trigger in a safe manner. Well nearly…
The thing about military rifles chambered in .303 is the chambers can be rather generous, after all they were designed to be used in war where a shot was fired and the spent cartridge case discarded. The military certainly were not interested in preserving fired cases and a generous chamber meant the round could be chambered in muddy or dusty conditions which it did admirably. The downside is the cartridge case which head spaces off the rim tended to rattle around inside the chamber when ignited, the shoulders would go forward however the rim would go back and this would lead to stretching/thinning of the brass just forward of the rim, this can be evident on even once fired cases where the stretched area of material is clearly evident.
This leads to case failure in time so if I have a new box of brass to work with I add an O’ring to the rear of the case just in front of the rim. This means when the bolt is closed the O’ring compresses and holds the case head tight to the bolt face and as the internal ballistics take place the case head stays where it is and the shoulder moves forward. Yes the case has stretched but in a far more manageable manner.
You can clearly see the difference in the shoulder position on this ‘Before and After’ image.I guess a picture of a case shot without an O’ring would be good at this stage however it would also seriously upset my nice neat rows of fired brass as there would be a gap.
I will look out for a stretched case and add it to this post if I find one.
Look carefully and you will spot a ring on the bullet just behind the meplat, this is where the seater stem has been cutting into the jacket as it is designed for a 174 SMK as opposed to a 150 grain soft nosed bullet such as the Pro Hunter here. I will machine a new seater stem to suit the profile of the 150 at some stage however as today was a combination of zeroing and blowing the cases neck forward it was not incredibly important.
So there you are, fire formed 303 brass that should last for ages with neck sizing only and an occasional annealing. Before you ask, the O’rings I use are actually those used on our .308 Cleaning Rod Guides and I leave the ordering of such things to the Viking and have long since forgotten the details, however if you would really like to know give her a shout and I am sure she will be able to help 🙂