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Thread: .303 British Case Separations - Causes and Cures

  1. #1
    Boolit Master
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    .303 British Case Separations - Causes and Cures

    .303 British Case Separations - Causes and Cures

    The combination of British Lee-Enfield rifles, odd chambers and thin brass have made this round my all time worst destroyer of brass - caused by partial & complete head separations.


    Background

    Lee-Enfield rifles


    1.The Lee-Enfield action is a bit elastic and that can add to the damage that causes the separations. I have calculated the momentary stretch with full power loads on the #4 Mk1 at

    .007 inch.
    2. In addition some Lee-Enfields can have a good bit of head space that can add to case stretching if you persist with FL sizing.
    3. The chambers are both extra large in diameter and extra long to the shoulder as compared to most ammo. Brass when fired has to stretch to fit the chamber to the shoulder and it has to expand diametrally to fit the chamber diameter. The poor diametral fit causes a lot of stretching at the solid head junction with the case wall. You can identify this stretch by the prominent pressure ring step in the case where the solid head joins the case wall.
    4. The Lee-Enfield chambers usually measure .460 at the big end of the chamber. US brass typically measures .450 to .452 at the solid head just ahead of the rim. That is too much expansion coupled with the other things that add to the damage. Acceptable expansion of the case would be more like .004 or less at the case head pressure ring step.


    Common Brass faults
    5. US made brass is light weight in the case wall thickness and US made brass, especially Remington, is way shorter than the chambers at the shoulder location.
    6. The over length .303 chambers did what the Brits needed but they stink for people trying to make expensive brass last. If you examine both CIP and SAAMI drawings for the cartridges and the chambers you will find they are very much like any other cartridge design where the cartridge actually looks like the chamber.
    However the British chambers have been impossible to document. It seems the Brits do not really have fully dimensioned and toleranced drawings for both the ammo and the chambers. If you collect enough once fired .303 brass you will eventually see a wide range of chambers including some that qualify as clown chambers.


    How to deal with all of the above?

    Start out with the best brass for the job and right now that is PPU. The head of PPU brass is larger in diameter at .454 to .455 and that will reduce the radial stretching. The PPU brass has a longer should
    er location which helps reduce stretching. It is also thicker in the case walls which helps resist stretching.

    You can try the following to see how much they help case life. One through four will only be needed for the 1st fire forming shot.
    1. Use small O rings or rubber bands around the case head to take up any head space by forcing the case against the bolt face.
    2. Expand the neck on new brass to about .35 or .375 cal. and neck back down to give a new shoulder with positive contact when the bolt is closed. This prevents so much of the shoulder from having to blow forward on the first shot.
    3. Wrap the case head with a .150 wide strip of .003 to .004 thick tape just ahead of the rim. Use enough tape (probably 1 full wrap) to center the case head in the chamber so the step at the solid head is spread around the full diameter and is not concentrated on one side by the extractor.
    4. If you are an advanced and motivated hand loader you can try using your FL die to hydroform the case body so the shoulder expands radially rather than stretching longitudinally. This is one of my next projects.
    5. For those that are familiar with a lot of fire forming, smooth chambers help. If you know how to polish a chamber without damaging it a light polish does no harm.
    6. You can apply a very light film of oil to help the case form without sticking to the chamber. This prevent the case from grabbing the chamber and stretching at the first shot.




    Once you have fired your brass the best you can do for it next is to keep it clean and neck size it with a dedicated NECK die such as the Lee Collet neck die or a common die for a fatter case like a .308 Win. with the proper .303 sized expander. Size only the upper 75% of the neck and do not touch the shoulder. Remember the Lee-Enfield chambers are nowhere close to the SAAMI dimensions of the US made loading dies. Once you get the case body expanded to fit your chamber you never want to size it again.


    Finally keep your loads mild so you never have to FL size it because I guarantee the inside of your FL die is not going to match your chamber unless you get a custom die made to match your chamber.


    Keep track of your brass. Examine it carefully before each loading for impending head separations.


    For reference only


    Case forming adventures tried


    1. .30-40 Krag
    About 20 years ago Krag brass made by RP and WW was about .455 on the head. I tried some of it and it worked OK for the most part. I did have one old case that separated without ever expanding the Krag shoulder forward. This one case might have been hinting that my pressure was too low and my powder was too slow expand the case before it pulled in two. The latest reports I have indicate that recent Krag brass is the same size at the head as current .303 brass. Check with a micrometer if you have any Krag brass.
    I still have a few Krag cases in a box of ammo with about 12 different .303 head stamps



    2. .444 Marlin
    This brass is about the right length but requires several steps to form the neck. The case head is also too large at .464 to .466 so it has to be swaged or turned down. Swaging the head will split the common .44 magnum dies that I used. I found that the case walls of the .444 are significantly thicker at the case head junction.
    .444 brass is so expensive now that I would not even bother. It did make long lasting brass and I am still shooting a box of it.


    3. .405 Win brass made by Hornady
    This was just a fun learning experience with 3 pieces. The .405 brass is tough and required several intermediate steps to form. The necks were too thick to chamber with a .312 bullet so they were turned and annealed.
    The rims are right at the max that my rifle will close on. One of the rims was too thick and needed thinning from the front of the rim. These are very tough heavy cases that would last a long time. But they are very expensive and require a lot of work. The best thing is the case heads are .458 to .459 and will just barely fit the chambers with almost no expansion. You would have to polish out the base of a FL die to avoid sizing the solid head of these cases.


    If all of these things don’t work the best I can recommend is some permanent modification of the chamber or rebarreling of the rifle. I have an idea for one change but I will not discuss it since I have not yet tried it.


    I have bought once fired R-P and Norma brass that had partial head separations from being fired with the factory loads. This is the only caliber brass that I have ever bought with separations from the first firing of factory ammo. So I will recommend do not get your brass from factory ammo or any once fired brass if you can help it. Some brass is of high quality but it is often damaged by the first shot at full pressure.
    Start with new brass and mild loads for longer case life.


    Always wear safety glasses with one of these rifles. I have had many case head separations because I was using someone’s once fired brass. I have never had a gas leak but there is always a first time.



    Last edited by EDG; 02-18-2017 at 03:11 AM.
    EDG

  2. #2
    Boolit Master
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    EDG, thank you for the comprehensive, and easy to read and understand guide for the 303, I have been putting off loading for mine until I did more research on extending case life, and now you have made things clear...denny

  3. #3
    Boolit Master

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    I nominate this thread for a sticky.
    'I have a feeling we're not in Kansas any more, Toto!' Dorothy, in The Wizard of Oz.

  4. #4
    Boolit Master
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    As previously posted, use good quality brass such as PPU or HXP and avoid S&B, as it suffers from a very limited reloading life.
    ukrifleman

  5. #5
    To find a more eternal theme, you would have to enter the realms of true love or revealed religion. Lee-Enfield headspace can be adjusted by the use of substitute bolt-heads, but people commonly find that that isn't a solution to the problem. The real villain of the piece is the diameter (rather than the length to shoulder) of front end of the military chamber, a problem more often encountered in the No4 than in earlier rifles. It wasn't too bad a choice in Europe, since armies don't reload and the only really major war since Napoleon had placed much more of a premium on reliability in bad conditions than on extreme accuracy.

    Neck sizing isn't a perfect solution. Cases will soon become sticky if a reasonable performance level is aimed at, and most commercial dies won't size the full neck without some reduction of the body diameter. Perfection, for the person enthusiastic enough to spend money, would be a custom made reamer to ream a die blank, available from Pacific. Lapping out the body part of a standard die, using a case with the neck removed, may also work. I would sooner do this with a lathe or some very precise holding device on a drill press, as freehand is easy to do lopsided. It will take time, and numerous grades of abrasive, to do remove metal at a reasonable speed and end up smooth enough when some body sizing is needed.

    Just in front of the rim expanding the case on the first firing won't do any harm unless your die keeps sizing it down and then up again. The 0-ring and taping it are both good ideas, usually, although there will be rifles for which they aren't enough. The copper adhesive tape sold for making reproduction Tiffany lampshades is good for this.

  6. #6
    Boolit Man
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    Headspace isn't really an issue. 303 headspace is on the rim like all rimmed cartridges. The issue is in the fact that the chambers are intentionally cut long so that the rifle can chamber dirty ammo. When you full-length size the brass it flows quite a bit. The result is short brass life. No amout of headspace tightening will fix it because, as I said, headspace is on the rim, not the shoulder. You can mitigate a lot of the problem by setting the sizing die up so that it doesn't make contact with the shoulder. I adjust mine so that there is about 1/16" of the neck left unsized. It also leaves a corresponding unsized ring at the base. This serves to center the case in the case in the chamber, and seems to greatly improve accuracy. All the benefit of neck sizing without the tight clambering and feeding problems. Another trick I've found is to run my brass through a die for a longer cartridge with the same head diameter. For example, I run .308 brass from my semi-autos through a 30-06 die first to size the base. This keeps the brass from flowing up as quickly, and makes my brass last longer. I'm not sure what die you could use on a .303. Maybe cut the top off an old .303 die.

    Your mileage may vary, but I was shooting 1/2 moa groups from my #4 when everyone was saying they weren't capable of better than 2moa because the action would spring. Same thing with my fal.

  7. #7
    The trouble with calculating or counting on how the action will spring, is that it doesn't always do it. Remember Ackley's experiments with a 94 Winchester and one of his Improved cartridges. He found that nothing untoward happened when the locking lug was removed, or even anything but expulsion of the primer when the barrel was backed out a thread and the firing-pin lengthened to strike it. The strength and adhesion of the case prevented any substantial pressure from being exerted on the bolt. The .303 is a very different shape, and often a different fit, from an Ackley Improved case. But action springing isn't a simple effect.

    Of course we do have to keep bolts and locking systems, even though they are such a nuisance. Cases can be wet or oily, or can have head separations. There are widely varying accounts of the effect of rainwater in Lee-Enfield chambers. Some say they are particularly susceptible to loss of accuracy, others not at all.

    The No4 action (and the No5 jungle carbine) is the only one to have a reinforced receiver. Except for the late Indian SMLEs this makes it the only Lee-Enfield suitable for the 7.62mm. conversion. But I haven't heard convincing accounts of superior accuracy to the earlier rifles, when condition and amount of bedding work etc. was the same. Incidentally the only Lee-Enfield from which I have ever taken a chamber cast was a long Lee-Enfield dated 1897, which had as conventional a chamber as SAAMI could have wished for.

    Sizing the neck a sixteenth of an inch short of the body, as you describe, will work with many rifles. But with some oversize bodies near the shoulder, the use of standard dies will still produce undesirable body sizing.

  8. #8
    Boolit Master
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    I had more than one Enfield, and didn't want to load separate ammo for each rifle. Fortunately, none of mine had grossly oversize chambers. I figured out which one had the tightest chamber, and found a piece of range brass that wouldn't come near fitting it; this is pretty easy since most range brass is apparently fired in oversize chambers. Start screwing the FL die down on the range brass just about a quarter-turn at a time until the bolt on your rifle will just kiss the sized case when closing without having to force the bolt shut. Brass sized thusly won't last as long as brass neck sized for individual rifles, but it's a good compromise if you want to simplify your LE reloading.

    I agree that excess headspace is seldom a problem with Enfields; it's most often brass that was fired in an oversize or out of round chamber.

  9. #9
    Boolit Master



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    I always set my dies for the amount of shoulder setback I want. Just because a case has a rim or a belt don't preclude setting proper headspace on the shoulder.

  10. #10
    Boolit Man

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    Quote Originally Posted by EDG View Post
    I have calculated the momentary stretch with full power loads on the #4 Mk1 at .007 inch.
    That's about what happens with my 7.62 NATO Ishapore 2A1. Loads that stretch .002" in a Remington 788, will stretch about .009" in the Ishapore.

    Yes, there's a certain amount of apples-to-oranges here, 7.62 vs. .303, and the 2A1 is more like a No. 1 than a No. 4, but FWIW my experience more or less agrees with EDG's calculation.

  11. #11
    Boolit Master
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    There really is no trouble at all with calculating how much the action will spring. It does not even matter if it varies. The damage it does to the brass is not imaginary.
    It is possible to affect the load put on the action due to the different chamber and brass fits, tempers, lubricating agents such as oil or water and surface texture.
    The fact that they can vary means nothing much to the engineer because the engineer has to design for the worst case condition. When the round fires and some condition prevents the full force from being applied to the receiver who cares?
    Everyone that shoots a Lee-Enfield does care when the full force is applied to the action. That is the worst case and that is the worse case for the brass too. The calculations are always done for the worse case condition.
    As anyone that has loaded a significant amount of ammo for a Lee Enfield knows that the load from firing a round does stretch the brass and ruin it to a worse degree than practically all other actions. The stretch calculations help quantify some of the rifle's contribution to the damage.
    Some of the issues for brass fired in a Remington rifle are discussed at Varmint Al's web site where he performed a Finite Element Analysis (FEA) of a rifle action.

    Quote Originally Posted by Ballistics in Scotland View Post
    The trouble with calculating or counting on how the action will spring, is that it doesn't always do it. Remember Ackley's experiments with a 94 Winchester and one of his Improved cartridges. He found that nothing untoward happened when the locking lug was removed, or even anything but expulsion of the primer when the barrel was backed out a thread and the firing-pin lengthened to strike it. The strength and adhesion of the case prevented any substantial pressure from being exerted on the bolt. The .303 is a very different shape, and often a different fit, from an Ackley Improved case. But action springing isn't a simple effect.

    Of course we do have to keep bolts and locking systems, even though they are such a nuisance. Cases can be wet or oily, or can have head separations. There are widely varying accounts of the effect of rainwater in Lee-Enfield chambers. Some say they are particularly susceptible to loss of accuracy, others not at all.

    The No4 action (and the No5 jungle carbine) is the only one to have a reinforced receiver. Except for the late Indian SMLEs this makes it the only Lee-Enfield suitable for the 7.62mm. conversion. But I haven't heard convincing accounts of superior accuracy to the earlier rifles, when condition and amount of bedding work etc. was the same. Incidentally the only Lee-Enfield from which I have ever taken a chamber cast was a long Lee-Enfield dated 1897, which had as conventional a chamber as SAAMI could have wished for.

    Sizing the neck a sixteenth of an inch short of the body, as you describe, will work with many rifles. But with some oversize bodies near the shoulder, the use of standard dies will still produce undesirable body sizing.
    Last edited by EDG; 03-04-2017 at 12:08 AM.
    EDG

  12. #12
    Boolit Master
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    I am not surprised. I once had a #1 Mk III and it ruined cases a bit faster than my #4 does. The results do not have to be perfect. All that is being illustrated is the magnitude of the action's contribution to the case stretching problem. Add another .007 of head space and these things start to compound the problem.

    I can add that the problem with the Ishy 2A1 is not nearly as bad as any rifle chambered for the .303 because you can find loads of 7.62 brass everywhere.

    Quote Originally Posted by gunwonk View Post
    That's about what happens with my 7.62 NATO Ishapore 2A1. Loads that stretch .002" in a Remington 788, will stretch about .009" in the Ishapore.

    Yes, there's a certain amount of apples-to-oranges here, 7.62 vs. .303, and the 2A1 is more like a No. 1 than a No. 4, but FWIW my experience more or less agrees with EDG's calculation.
    EDG

  13. #13
    Boolit Master taco650's Avatar
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    This has been an interesting read. My solution for making cases last in my #1, Mk 3 is neck sizing with a standard FL die (RCBS). It has helped but I have had my share of head separations, so many that I bring a cleaning rod with me when I take the .303 to the range. I was given some once fired brass recently & my plan is see if it chambers as-is and if so, neck size it only. If not, I'll FL size it only enough to get it to chamber. I've noticed that the shoulder on my fired cases is about a 16th further away from those that FL sized but I'm just guessing.

  14. #14
    Boolit Master

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    I really have to get out and get some shooting done... not just for .303, I've been away from the guns for a bit now and missing them.

    I have had no head separations in any of my .303's though some have hardly been shot. I have 2 No. 5's and my son has one, I have a sporterized #4 MK I and a No. 4 MKII in very good shape. However, I have shot primarily cast boolit loads at moderate levels.

    My plan was to mark some brass so I can keep track and record loads and numbers of firings to see how long the brass lasts using full loads. I have to admit I have been sloppy and just shoot then dump the brass into a container until I am ready to tumble then reload so brass is mixed and I don't know how many reloadings they have had.

    I only neck size using a Lee collet die and I made a mandrel to suit the 0.315"+ boolits I use so the neck is not overworked sizing it down to 0.310"/0.311" as my RCBS dies do. I am also somewhat lucky in that my No. 5's and the No. 4 MK I all share brass. The No. 4 MK II has a tighter chamber so brass shot in the others is a very tight fit to chamber if not full length sized. It goes but it is tight.

    As taco650 says if I full length size the shoulder is pushed back about 1/16" or maybe a little less but a lot! I don't think there is anything close to that for radial expansion so not sure why they would have made the chambers so long... dirt doesn't just sit on the shoulder but that is where the most clearance is and that movement of the shoulder each time if full length resized must be very hard on brass.

    Anyway, this thread has me wanting to get some shooting and testing done. Time to dust off the guns (and reloading gear).

    Longbow

  15. #15
    I still think the main source of a difference in case life between .303 and 7.62mm. in substantially the same rifle is the case shape and chamber shape.

    When the relatively straight-bodied 7.62mm. case (or even more so an Ackley Improved design) expands, that slight stretch is distributed all along its length. In the Improved cases (the .300 Savage AI being the one I have sectioned, there is often a reversed taper in the interior space, producing a tendency, if brass creeps on steel, for it all to creep rearward. In the .303 the interior space tapers towards the shoulder, even more than the outside does. There is a tendency for the body to be forced forwards while the head and immediately adjacent area is forced rearward. So naturally repeated use causes the case to part at the usual point.

    It was a pretty good bet for a military rifle that will fire cases only once, and sometimes in extremely bad conditions. We think the straighter the case, the easier it is likely to extract. But that is for a meticulous rifle enthusiast's chamber. In military service, with the chamber dirty and perhaps even pitted, the intuitive idea of the more taper the better does often work out.

    That headspace isn't an issue wasn't my idea. It just doesn't solve the issue on its own. But the part of the problem that lies in the chamber shoulder will surely be reduced if the bolt-head headspace adjustment brings the case rim as far forward as the rim recess permits.

  16. #16
    Boolit Master Moleman-'s Avatar
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    Great thread! I've always kept 303 brass with the same rifle and sized them just enough to chamber easily. It's easy now as I'm down to just a #5 at the moment. Regret selling my #4MKI.

  17. #17
    Boolit Master
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    Thanks for the post, had a near full separation on Win military brass the first time reloaded. White box from the 1980's. Will be checking the rest with a wire before the next go around.

    Plan on using the o rings the next time and keeping for that particular rifle only.

    Also tried the 444 cases, will need some material to be removed for sure.

  18. #18
    Boolit Master
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    If you can, find a .308 Win FL die and put the .303 expander in it. Neck size the upper 75% of the neck with the .308 die so you do not move the shoulder back any.
    There is a lot of difference between loaded ammo or factory new brass and the location of the shoulder with once fired cases. Let the fired shoulder stay where it is.

    Quote Originally Posted by taco650 View Post
    I've noticed that the shoulder on my fired cases is about a 16th further away from those that FL sized but I'm just guessing.
    EDG

  19. #19
    Boolit Master Traffer's Avatar
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    Maybe you would like to know this:
    A guy gave me an Enfield 303 when I was 14. It had been traded in to a local sports store. I only shot it about 10 or 12 times. I think any one of those could have blown my head off. The cases were almost all ruptured at just above the head. People who knew guns said "too much head space" and warned me of the obvious danger. I did an experiment one day. I unscrewed the bolt head one full turn and tried to chamber a round. It chambered perfectly. I was more afraid to shoot it that way instead of looser because it seemed that those threads may not hold the pressure. (remember I was 14) So I shot it in a way that I had my head down behind a big chunk of wood when I shot. In case she would blow up. The shell came out without the rupture or huge bulge. I used it for deer hunting for a couple of years but maybe only shot it 2 or 3 more times. The last time I shot it a buddy was watching and said, "holy cow, did you see that?" "What," I replied. He said that there was a foot high flame come out of a hole on top of the chamber. Being concerned that someone else might have it blow up, I took it by the barrel and wrapped around a telephone pole. I have always been wary of the Enfields because of the obviously weak locking mechanism. It surprises me that they will hold the pressure even when they are in good shape.
    Jedediah Morse
    "To the kindly influence of Christianity we owe that degree of civil freedom, and political and social happiness which mankind now enjoys. . . . Whenever the pillars of Christianity shall be overthrown, our present republican forms of government, and all blessings which flow from them, must fall with them.".







  20. #20
    Boolit Mold
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    If it may help. About fifty years ago I had the opportunity to visit the Navy arsenal in my home town when our sailors still had the glorious No.1 MkIIII most being WWI refurbished for guard service and basic training. Well, in reassembling process of course they checked the bolt head for the correct headspace with go-nogo calibers then they choosed the suitable bolt head among a bin full of them. Now I cannot remember if each bolt head was numbered for an easy identification, but it's possible, anyway for sure boltheads on the market are not all the same but there are many different sized bolt heads to try for headspace. I can image that bringing the headspace at minimum the risk of case head separation will greatly reduced.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check