The problem with '303 case-head separations may not all be down to rim thickness.
.303 headspaces on the RIM, not the case shoulder , like sensible rimless cartridges..
Your "surp-mil .303 rifle has had its chamber "refreshed, (to clean up roughness , the brass at the front end will expand more than usual. Depending of the "annealing", if you full-length size your brass for optimal feeding, that could be a LOT of metal fatigue going on there... The usual manifestations, in order of "annoyance" being: cracked necks, blown shoulders and case separations.
Forty to fifty thousand PSI exerts a LOT of encouragement for the brass to "flow".
Likewise, squeezing it all back to SAAMI dimensions in your trusty Rockchucker, makes the brass flow inwards AND forward. (Hence, why experienced / well-trained reloaders TRIM their rifle brass, especially)
IF you have ONE.303 rifle, use the neck-sizer die and the full-length die, . And an annealer. The FLS die is used to do a "general" resizing. It is backed off a few turns. Then the neck-sizer is adjusted slowly until the empty, sized brass JUST drops smoothly into the chamber.
Trim and inside chamfer as desired / needed.
If you have a bunch of different models and conditions of rifle, you have two basic options:
"Custom" case processing for each rifle, or, "universal" sizing (one size fits all), and buy bulk brass when it turns up on "special" sale.
And DO NOT use boat-tailed bullets in ANY .303 Lee-Enfield, Ross or P-14.
Or, buy an Ishapore 2A1 and enjoy shooting without fretting about all that brass management,
Once fired cases are now shoulder spaced which is why you only use Lee neck size die. FLS die return the case close to being to small hence case head separation.
Trimming for length is reduced to a maybe some time down the track. Annealing stops the neck splits and shoulder cracks. The better the brass quality the longer the life.
I do use open based boat tailed projectiles. I have bullet making gear and a nib that turns Mk8 type projectiles into Mk7 projectiles. Just think outside the box.
No to the 2a1 Indian because they are proofed only to 144gn projectiles which are a little hard to find as a NATO loading. These rifles are NOT 308 compatible.
Just like the L42a1 is not 308 compatible only use 144gn NATO load they are a 303 conversion to the NATO load which is at the outer limits of their strength.
The civvie No4 target rifle conversions are the same and have been banned from use from target shooting in most Commonwealth countries.
If you want to continnue shooting these old girls do so just do your home work down load the ammo to the original spec and use dies and projectiles to help do this even if the only option is hard cast to fit the bore.
There is no real reason why they cant be fired for another 100yrs if looked after today. They aren't made any more so look after them.
An animated 'gif' produced some years ago by forum member Parashooter, showing why / how a sloppy head space COULD cause separations, particularly when combined with thin wall (SAAMI) cases.
Your headspace could be in spec at 70 thou, but using a thin rimmed case of (say) 58 thou means you have a 12 tho 'head clearance' allowing the case to stretch by 12 thou, and the weakest part (just above the web) goes 'pop'.
For me it is an excellent learning aid.
Last edited by Alan de Enfield; 02-06-2025 at 07:36 AM.
Mine are not the best, but they are not too bad. I can think of lots of Enfields I'd rather have but instead of constantly striving for more, sometimes it's good to be satisfied with what one has...
Prbably mangled my description of the "right-sizing" caper.
Yes, neck size for heck "grip" and shoulder contact.. The partial use of the FLS die (not touching the shoulder area, is to just reduce the case body (tapered) diameter for a close fit (not "tight) . Yes, it is essentially "headspacing" to the shoulder, a la rimless cases. If, like me, you only have ONE rifle in that calibre, it is no great challenge to build "matching" ammo. If you are dedicated lucky enough to have a whole fleet of them and you want to shoot most / all of them, have fun..
Related: who sells the "base bumping" gear?
I have almost a thousand thousand Mk 8 bullets that need "rectification".
Last edited by Bruce_in_Oz; 02-06-2025 at 04:55 PM.
An animated 'gif' produced some years ago by forum member Parashooter, showing why / how a sloppy head space COULD cause separations, particularly when combined with thin wall (SAAMI) cases.
Your headspace could be in spec at 70 thou, but using a thin rimmed case of (say) 58 thou means you have a 12 tho 'head clearance' allowing the case to stretch by 12 thou, and the weakest part (just above the web) goes 'pop'.
For me it is an excellent learning aid.
And of course the case is often is not fully enclosed in the chamber when ignition occurs; the amount of unsupported case wall at the base in such instances is more like the final position shown in the GIF.
And just off hand I suspect that larger chambers in conjunction with excessive heads space are even more prone to this kind of separation as the farther the case has to expand before chamber wall adhesion takes effect the longer the rearmost portions of the case are exposed to the full(?) pressure of the charge.
Last edited by Surpmil; 02-07-2025 at 01:19 PM.
“There are invisible rulers who control the destinies of millions. It is not generally realized to what extent the words and actions of our most influential public men are dictated by shrewd persons operating behind the scenes.”
yes Surpmil.
With good quality metal Brass in large chambers case head separation is not an issue at first firings. With poor metal quality brass in tight chambers case head separation still occurs at first firings.
Good quality brass is a deep golden colour almost brown, the poorer the quality the lighter and whiter the colour of the metal. As in all things man made there are exceptions the colour can be right but the malleability is not.
The British Military Brass specs had to cover these issues. I have NEVER had a case head separation using military ammo in any military 303. All case head separations have been CIVVIE brass
Unless you're shooting a fresh, out of the wrap, 1955 Fazakerley No.4 or an SMLE of No.4 rifle rebarreled with a new military or commercial barrel, boat tail projectiles like the Sierra Matchking are a waste of money.
I guess my rifles didn't get that memo. My LB and a couple of other Lee Enfields I own absolutely love 174 gr. SMK and LeHigh Defense 150 gr. boat-tailed bullets with their used barrels. I too tried the 180 gr. Pro hunter along with a dozen other bullets and only one outshot the SMK or the LeHigh incrementally and that was the flat based Hornady SST 150 gr. Can we all finally agree that Enfield rifling may not have been designed to work with boat-tail bullets but with a little patience and load development will shoot them just fine?
I fully agree that any company that recreates the Mk 7 round won't be able to keep up with demand but I've gotten by for 40 years now handloading the .303 British with good results.
Sapper 740
Its not the rifling its the erosion caused by the cordite which open based projectiles hide by bumping out to seal the barrel then sizing back down whilst moving down the barrel.
I am a F Class shooter ( 30 06 AI ) and have had a barrel fail on me when the gas beat the projectile to the rifling leaving the projectile pushing molten metal out the muzzle. The accuracy went south very quickly. 12 shots fired in that detail.
Sapper 740
Its not the rifling its the erosion caused by the cordite which open based projectiles hide by bumping out to seal the barrel then sizing back down whilst moving down the barrel.
I am a F Class shooter ( 30 06 AI ) and have had a barrel fail on me when the gas beat the projectile to the rifling leaving the projectile pushing molten metal out the muzzle. The accuracy went south very quickly. 12 shots fired in that detail.
I have posted this before. But I'll post it again .....................
Use of Cordite in Rifles
'Regulations For Army Ordnance Services', Vol.3, Pam.11A (1949) comments:-
USE OF .303-IN CORDITE AND N.C. AMMUNITION
1. The action of Cordite propellant in the barrel of a .303-in. weapon is quite different from that of N.C. propellant.
Cordite gives a rapid build-up of pressure with great heat, leading to pitting and erosion of the chamber end of the barrel.
N.C., however, gives a more gradual build-up of pressure with less heat, and this in turn gives uniformity of barrel wear from chamber to muzzle, the amount of pitting and erosion being greatly reduced.
2. With Cordite propellant, set-up of the bullet is most pronounced and even when the chamber end of the barrel is well worn, the muzzle end still has sufficient rifling left to impart the necessary spin. As the wear advances up the barrel, so the accuracy of the weapon is progressively reduced.
With an N.C. propellant, set-up of the bullet is slow and by no means so pronounced, due to the more gradual building up of pressure. The barrel retains its original accuracy until wear reaches a critical stage, when a sudden falling off in accuracy occurs.
3. It can be seen by comparison with the effects of barrel wear that to use N.C. ammunition in a barrel which has fired Cordite will give serious inaccuracy in flight, whereas the use of Cordite ammunition in a barrel which has fired N.C. gives good accuracy, but serious changed the wear pattern of the barrel.
In the first case, i.e. a weapon which has fired Cordite ammunition the barrel will be eroded and fissured in the first few inches up from the chamber, the part in which obturation should occur. The poor set-up of the bullet, in the N.C. cartridge is not sufficient to give good gas sealing in such a barrel and the bullet does not, therefore, receive the maximum impulse. The resultant loss in velocity and instability due to lack of spin lead to a high degree of inaccuracy.
In the second case, Cordite ammunition fired from a barrel which shows uniformity of wear from firing N.C. ammunition, has an adequate reserve of set-up that ensures full gas sealing, with satisfactory velocity and spin. Unless the barrel wear is in a advanced stage due to firing a large number of N.C. rounds, there will be no immediate appreciable loss in accuracy. Furthermore, the decline in accuracy for Cordite ammunition will follow the normal gradual fall-off experience in weapons firing Cordite alone, as the wear at C of R progresses.
4. Trials have proved that even if only a few rounds of Cordite ammunition are fired from an "N.C." barrel, the ensuing accuracy life when N.C. is subsequently fired is reduced considerably. The occasional and restricted use of N.C. in a "Cordite" barrel will however, have little effect on its ensuing accuracy life for Cordite, although naturally the fire of N.C. will not be very accurate.
5. The effect of wear of barrels can be determined by firing shots through a paper screen at 100 yards. If, on examination of the screen, all shot holes are not perfectly round, then the barrel is no longer fit for use.
The danger lies in the fact that bullets fired erratically from badly worn barrels may overcome their instability in flight and take up a steady flight in the direction in which they happen to be pointing, with short-ranging and disastrous results if used for overhead fire. Except under these conditions of long-range firing there is no risk involved, though in normal range firing inaccurate fire will result.
6. The following instructions regarding the use of .303-in ammunition have been issued to users and are governed by stocks and types of ammunition and weapons in current use:-
(a) .303 in. Vickers M.G.s in M.G. Bns.
(i)Mk.8z only will be used for overhead firing.
(ii) Mixed belts, i.e. Ball, Tracer, A.P., etc., will NOT be used.
(iii) Any barrel which has fired Cordite ammunition will NOT be used for N.C.; barrels will be stamped “7” on the trunnion block and returned to R.A.O.C. through normal channels.
(iv) Barrel life for N.C. will be assessed by unit armourers using the appropriate gauges.
(b) .303 in. Vickers M.G.s in A.F.V.s.
Here the overhead fire problem is not considered; the range is usually less than is the case with ground M.G.s. tracer ammunition is required as an aid to fire control, and prolonged fire programmes are not envisaged. Special mixed belts of Mk.8z and Tracer are provided in boxes clearly marked “For use in A.F.V.s only”. The reduced life of the barrels is accepted.
(c) Light M.G.s.
Cordite ammunition normally will be used. N.C. ammunition, however, gives a relatively small flash at night and if the Bren is being used for a special purpose, e.g., on a patrol, its use is permitted.
(d) Rifles.
N.C. ammunition will not be used in rifles except in such circumstances as quoted in para. “(c)”
above, if necessity should arise.
7. Belt packed S.A.A. for M.G.s is packed in boxes which are clearly marked with labels or stenciling indicating its proper use. It will never be de-belted and used for practice purposes in L.M.G.s or rifles.
8. It must be noted that the above restrictions apply only to ammunition fired from British weapons. All American ammunition is N.C. loaded and their weapons are designed to fire it satisfactorily.
Mine are not the best, but they are not too bad. I can think of lots of Enfields I'd rather have but instead of constantly striving for more, sometimes it's good to be satisfied with what one has...
PM
Originally Posted by Alan de Enfield
