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  1. #11
    Advisory Panel browningautorifle's Avatar
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    Polishing a chamber will take metal off and increase the headspace problem, not help. You have a headspace problem. It should run with all ammo not some special ammo that you can't get. RG isn't something godsend, but you can't try it so it's out. US issue ammo should work fine. Work towards a headspace that's tighter and your separated cases will stop.

    Regards, Jim

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  3. #12
    Senior Member WallyG.'s Avatar
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    Good eye on the missing front sight lug...this implies that a flash hider was grafted to a barrel... an original has the locator tabs on each side - also barrel looks too thick to me to be UKicon - in profile forward of the gas block and its missing the locator lug on the underside to mate with the receiver. OP When you say its marked "Enfield"... is that actually spelled out in a stamping? UK contract barrels have multiple small proof stamps and a used barrel would also come with one or more serial numbers struck in it as well. All should be stamped between the barrel seat and the carry handle. If this area is sterile... lack of markings and the profile deviations mean its most likely a new production barrel. So... Suspecting that this is in fact a SARCO barrel... the case separation solution still resides in the dimensions of the headspace and the chamber... you need an experienced gunsmith to assess both. As for locking shoulder and bolt... if the bolt is a real .308 it should be marked as such... can you provide images of the bolt markings? Original .308 barrels use specific bolts and locking shoulders because the breech face is a different geometry than for the .303 guns. I presume the SARCO barrels are made to the .308 breech face dimensions and not .303. Also, there could be receiver dimensional issues when welded back into semi form... again an experienced gunsmith will be needed. I wonder if the bolt is hitting the bolt stops before coming into contact with the case - producing too much headspace. if welded up slightly off in the mag well dimension/length this can come into play and no new locking lug can adjust for the bolt bottoming out on the stops prematurely. Anyone else have any more suggestions? Unfortunately, most of the implied issues are not easy for a DIY user to remedy. Good luck!

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  5. #13
    Member SleepyDoc's Avatar
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    I guess this is my fault for not including more pictures initially. The barrel is as described. original UKicon, Enfield manufacture.
    I was wrong. Never should have trusted my memory. It is in fact a Mk3, converted to L4.
    Bolt is also Enfield.

    Not ideal to have it close on a 308 no-go, but considering the 7.62 max is the MAX for a 7.62 it is theoretically still safe. I would prefer a tighter chamber and I could have the barrel altered to set the chamber back, but I wanted to try less destructive things first. Something like polishing the chamber. If that or other less destructive methods don't work then I can have the chamber set back and re-check headspace. I will probably need a gunsmith to do the latter for me for safety concerns and so I don't mess up the whole barrel. There is enough room from the receiver to the locking block to do this at present time.

    I will try to find some throat erosion gauges or measure some spent brass cases to see if there is excessive expansion. The chamber does appear to have more scratches and irregularities than I remember as is evident on the cases. It is hard to believe that would cause anything, but weirder things have happened.

    If anyone else has recommendations on how to polish the chamber or what tools to use, please let me know. Any idea what size of shotgun mop would work best? Is flitz the best to safely polish without taking off too much material? I saw someone use a mop or something with high grit sandpaper, but that seems a little much to me.

    If anyone has other ideas I would also like to hear them before going down this rabbit hole.

    I can also supply any other information or pictures if it would help someone to make another diagnosis or figure something out.

    Thank you all for your help in this matter. I will update you as I make alterations based on your input. Given my terrible schedule right now it might be a bit to get something done, but I will try to keep you all in the loop.
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  6. #14
    Really Senior Member tr63's Avatar
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    I would like to see how you are going to set back the chamber to cure your long head space ? Are you going to shorten your barrel and use a .308 reamer to rework the long head pace ? If you do the barrel locking treads will need to be reworked the locking nut will be in trouble , the gas piston will need to be shorten, the gas block on the barrel will have to be relocated because the barrel was moved rear ward . You only need to do is change out one item and that is the bolt locking shoulder with one that longer it is held in with one screw !!! Stop making you chamber longer or larger in dia.. What are you taking about when you refer to 7.62 max. as being safe for a Bren in .308 cal. ? What 7.62 gauge I hope not the one for 7.62x54r .
    Last edited by tr63; 01-25-2021 at 11:41 PM.

  7. #15
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    Anyone have a source on 308 locking shoulders? I will have to measure mine. I know 303 guns have various sizes, but it seemed at a quick glance that 308 guns were not the same. Basically the ones I have found don't list a size. it is just a part with no guarantee if it will help my headspace. Any information or sources?

  8. #16
    Member SleepyDoc's Avatar
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    Max headspace gauge:
    https://www.forsterproducts.com/pdf/...2018_print.pdf

    Stolen from another forum:

    Headspace lengths for caliber .308 Winchester
    1.630" GO
    1.634" NO GO ??????????
    1.638" FIELD REJECT

    The G.I. Headspace Gage lengths for 7.62mm
    Go Gage...................................... 1.6355"
    NO Go Gage................................ 1.6375"
    Rebuild Maximum Gage.............. 1.6415"
    Field Reject Gage....................... 1.6455" (MAX)

    As I said, max headspace gauge for a 7.62x51 chamber. Yes, I know 308 and x51 are similar. As I understand it SAAMI specs are still different. Please correct me if I am wrong. My gun headspaces within the max gauge I have, but it doesn't necessarily mean it is appropriate for the gun. Obviously something is happening. Still trying to figure out if it is purely headspace or something else. This is why I am asking for help in trying to figure out things. If I can find a locking shoulder that fixes the problem, then great. I didn't have to destroy any material. As of right now I know the headspace is somewhere between the max 7.62x51 and 308 no-go gauge, so it may only need a small correction to fix. However, I will have to work up the algorithm at some point to make other modifications if that doesn't solve anything. I.e. if it isn't actually a headspace issue and polishing chamber, or other part changes may be needed. There are lots of things that could be wrong, and lots of ways to fix those problems. Heck, you could drill it out and sleeve the chamber if you wanted to correct the headspace issue. There are near infinite possibilites of things you can do. Doesn't mean I want to do them or should do them. If I could find a barrel for a reasonable price to swap out and try I would do it. I will start at the locking lug which seems easiest and work from there.

    I will repeat, I am definitely not an expert an am still learning about the intricacies of the L4A4. Some of the things I may say may seem silly, but with what little knowledge I have they seem appropriate as of right now. As I learn more that will change.

    I appreciate everyone's input and I at least have a starting point to start the investigation. I will try to order a few locking lugs and see if I can get lucky with one that is longer. Hopefully there is a good return policy. After that I will see what the next step is. Since people keep adding input my steps may change base on practical and less invasive measures then work up.

  9. #17
    Really Senior Member tr63's Avatar
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    Gun Parts Corp. has locking shoulders .they do not sell them by size . They are selling them around $10.00 or less they all so have the locking shoulder screws to go with them .You can buy 3 or 4 and see what you get luck of the draw . Get a couple of the screws as well . You well need a good fitting large screw driver to remove the screw . The screw head it is located under the mag. latch . Pull the retainer pin for the latch and the ejector they will lift out , you will now see the head of the locking shoulder screw . Secure the your receiver in such away that you can apply force with two hands to the screw driver to remove the screw . note: the screw is staked to prevent it from shooting loose . With the screw removed the locking shoulder can be removed and you can measure it for length . I would wait un till you get your parts from Gun Parts Corp. before you remove your existing locking shoulder. hopefully you will get a locking shoulder that is longer/larger than the one in your Bren presently . If you have a replacement that is longer than the one in the gun you can install it and recheck the head space ,the bolt should not close on a field gauge but close on the go gauge . Note : A too long locking shoulder can be shortened by using a surface grinder . This is best done by a gunsmith that has worked on a Bren gun and understands it's workings . When you do the final locking shoulder install the screw must be re-staked to insure the locking shoulder will not shoot loose !!! Can you use or know how to use a digital calipers to measure the locking shoulder ?
    Last edited by tr63; 01-27-2021 at 12:38 AM.

  10. #18
    Advisory Panel browningautorifle's Avatar
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    Bren locking shoulders... I don't think it's a good idea to drill out a chamber and try to set in a sleeve.

    30: Bren Locking Shoulder (SIZE 2) - BRP CORP

    Bren Locking Shoulder - SARCO, Inc

    L4 Bren Locking Shoulder, 7.62mm NATO, *Good*
    Regards, Jim

  11. #19
    Member SleepyDoc's Avatar
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    I ordered 6 locking shoulders and 3 screws from Numrich (e-gunparts corp). Their return policy should let me return an envelope of parts weighing less than 1lb for free within 90 days or so. I also ordered another firing pin so I can make another one if needed. It also helped me to get enough in the cart for free shipping. I can only assume since multiple people have told me to get any locking shoulder that it should be the same geometry roughly. Finding an original 308 marked locking shoulder will be tough and some of the places you gave me links to were out of stock anyway.

    I will measure mine then the others and if I get a longer one I will update you all with what the headspace gauges show. Hopefully Over the next month I can get it all put together and maybe find some time to trudge through the snow to make some holes in paper for you all. Preferrably without case ruptures this time.

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  13. #20
    Really Senior Member Kev G's Avatar
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    303 locking shoulders will all be to big for a 'standard' L4A4 and if grinding down will probably need re-surface hardening.
    Have attached info on locking shoulder sizes for reference.
    303


    7.62


    As others have said this is not an Enfield or Interarms barrel but would be interested to know how many grooves the barrel has ?

    Not that it has anything to do with your problem but S/N A5197 shouldn't be dated 1967 as it was a batch of 180 L4A2/L4A4's dispatched to Weedon in March 1960 ?
    Last edited by Kev G; 02-01-2021 at 05:22 PM.

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