Getting Best Results From Your .303 British Cases

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   A frequently heard complaint is that "Lee Enfields all have excess headspace" and "Lee Enfield brass only lasts a couple of reloadings".

Urban Legend BullSchiff.  The reality is that the "Lee Enfield excess headspace problem" primarily only exists between the ears of unknowledgeable American gun writers and reloaders.  

You don't hear the same whining and whinging from Commonwealth nation competitors reloading for Service Rifle competition i.e. the Canadians, Brits, Aussies, etc.  And some of the better of that lot, once handloading became legal, have been running very stiff loads through their rifles, whether the usual .303 British or rifles like the Canadian DCRA conversions that are rechambered to 7.62

This is a .303 British handloading topic where there is a lot of supporting background detail and corporate knowledge available to throw out there to discuss and opine about.  Much as I enjoy that sharing and discussion, for the sake of this being a basic primer, I will try to avoid going into the nuances and context of that in this post as much as possible.

For best results, whether just case life and/or best grouping results during load development, this is the basic workflow to achieve that objective.  It is a one time process only done prior to first firing of your new brass to minimize and control the stretching of the brass on first firing.  It does not have to ever be repeated again with that brass:
Start with quality virgin unprimed brass.  For the .303 British, that would be Privi Partizan brass available from Grafs and elsewhere.  As others and I have discovered after making measurements of Mark VII military ball cases from various arsenals during and after WWII and comparing them to the commercial offerings, the only commercial brass that closely replicates Mk VII military brass is PP. Several have written up their findings after going through this comparison process if you want to search and find them.  (I published mine as well, but wherever I published those comparisons (Milsurps?), I can't find them now.) 

In particular, where rim dimensions are concerned.  That matters when highly successful fullbore competitors like James Sweet have written that best results will be achieved with the Lee Enfield rifle when your ammunition has .003" headspace.  Thin commercial rims from American manufacturers following SAAMI's standards (who are wrong on just about every measurement concerning this cartridge) do not help.

Do initial case preparation as you would for any other rifle you intended to handload quality ammunition for: trim all cases to the same length and uniform the flash holes and primer pockets while inspecting each case for obvious manufacturing defects (they do happen, including with PPU brass).

Using a Lyman .33 size M die, expand the case necks up to .338 caliber.  Prior to finding the .33" M die, used my .35 M die that I had for cast bullet loads in my .358 Newton.  A .35 neck expander die WILL work... but you will collapse and lose a few cases in the process.  Much easier and no lost cases if you spend a few bucks to buy the .33 M die.

Now put a full length (or neck sizing) die in your press, and start resizing the case necks back to .303 caliber just a little bit at a time.  Attempt to chamber the case after every incremental increase in the amount of case neck you're resizing.

At first your new cases will not chamber - the bolt will not be able to continue going forward due to the part of the neck that is still oversize.  Continue doing this until you have finally resized enough of the neck to allow the cases to completely chamber and the bolt to close with a very light crush fit.

      To skip ahead; your full length resizing die at this setting should be just about right when
       you reach that point in the future where you have to eventually bump your case shoulders
       back a bit.  

You will see that you now have a "false shoulder" that is some distance in front of the shoulder the cases came from the factory with (poor quality cellphone pic):

You do not achieve anything by just resizing the case necks enough that you end up with a tight crush fit when the bolt closes versus a light crush fit.  That is not better; that is worse.  For various reasons, you do not want a tight crush fit.

Optionally at this point, take the extra time to ensure your case neck resizing allows all your cases to chamber in the same manner.  They almost certainly all will, but you can take a few moments to ensure they will.  I don't, but you can.  

If one from the brass you purchased won't chamber for some reason after the neck resizing process, you'll find out when you attempt to chamber that case after it's loaded.  No harm other than annoyance.

Your cases are now "fire-formed", without ever being fired and any initial stretch on first firing.  They are centered in the long axis of the chamber, supported at the rear with the base of the case tight against the bolt face and supported and centered at the front with your newly formed "false shoulder" in contact with the circumference of the shoulder portion of the chamber.

At this point, handload your prepared cases as per normal.

After firing, DO not resize with a full length resizing die.  Neck size only!  If you do full length resize following the instructions that came with your reloading dies, you have eliminated all the case forming you have so carefully done and reduced the cases to being undersized for your chamber.  On the next firing, you will get the undesirable and destructive brass stretching that you were attempting to avoid and which dramatically shortens the life of your brass.

After firing, use only a Lee Collet Die (my #1 choice) or neck resizer to resize the fired cases.  Eventually after multiple loadings you will find some cases take more effort than a light crush fit to chamber after reloading.  At that point, do bump the shoulder back a few thou with either a bump die or just enough resizing with a full length die adjusted to just get back to a very light crush fit.
That's the basic outline of how to select and prepare your .303 British brass for best case life and performance.

You can do something similar with "the O-ring trick".  That technique for case prep prior to first firing does indeed hold the rim back against the bolt face.  But everything forward of that is drooping down, unsupported anywhere in the Lee Enfield's large chamber, left to expand wherever it wants on first firing.

There is no guarantee you will see noticeable differences by forming a false shoulder for case preparation versus the O-ring technique.  But the addition of centering the case in the longitudinal access of the chamber by supporting it at the front cannot possibly hurt.

One final thought: case neck annealing also offers the potential to improve both case life and grouping potential.  Hardened case necks cracking is another source of cases failing and being scrapped, and inconsistent neck tension due to work hardened necks is detrimental to consistency and grouping.

While there is no benefit to doing it as I do, anneal after every firing as part of the process of inspecting and depriming fired brass, it takes very little time to do this per case.  Most shooters other than those in the benchrest type extreme accuracy disciplines feel annealing about every five firings is sufficient.

I do not have an annealing machine, the best (and most expensive) option.  I do it as the benchrest competitor and metallurgist described in an article of Precision Shooting: I hold the case by the base between my fingers while turning the neck and shoulder in the flame of a lab alcohol lamp.  When the base gets too hot to continue holding in your fingers (only a few seconds), drop it on a cloth and continue with the next case.

The alcohol lamps and 99% pure alcohol for fuel are only a few dollars on Amazon and elsewhere, and using 99% alcohol instead of an even less expensive candle results in very little smoke and soot on your cases needing cleaning.

This is not the very best way to get the very best annealing results, but it close enough that what it lacks isn't going to detract from the results while handloading for the .303 British.

For your information and consideration...