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  1. #1
    Really Senior Member AmEngRifles's Avatar
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    L4 mag issues

    I wish we had a "semi autos" only section as most of my question will all now relate to the semi auto builds done here in the US. I doubt many other locations are doing them, meaning what other country around the globe would have the legal and financial emphasis on doing such a thing?

    My L4 has been experiencing quite a few bolt over base jams. I do not necessarily think they are all induced by lack of gas, meaning short stroking, BUT THEY COULD BE?? I feel like the mags themselves may be allowing the cartridge to be stripped, but either not feed correctly (possibly due to mag spring issues) or possibly a short stroke due to the added spring used to drive the separate striker in the firing system?

    I have been experiencing this and have not come to a completely satisfactory solution. I did try stretching the springs out a bit to get a more positive cartridge to feed lip interface. That seems to have worked on one mag, giving me a full 20 round feed without an issue, but not successful with all mags. Of course, added spring pressure on the cartridge would only mean more stripping power is needed from the drive springs.



    With these semi auto rebuilds, it seems to be such a delicate balance between drive springs, striker spring and magazine spring to get the whole thing running properly. I am suspicious that having the 3rd striker spring in the system may mean that the gas needs to be opened up a few thousandths on the largest setting, because not even the largest setting is giving complete reliability.

    Are these magazines known to allow bounce of a cartridge so that it may start to feed, but somehow the feed horns get off the base of the cartridge and slam into the partially fed case jamming it between the bolt and the chamber? Just curious to see if this event EVER occurs in the full auto L4??

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    Advisory Panel Lee Enfield's Avatar
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    Are you using 30rd L4 mags or 20rd L1A1 mags?

    With the mag inserted, can you lift the ejector block when you push the maga zine forward?

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    Really Senior Member AmEngRifles's Avatar
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    Quote Originally Posted by Lee Enfield View Post
    Are you using 30rd L4 mags or 20rd L1A1 mags?

    With the mag inserted, can you lift the ejector block when you push the maga zine forward?

    I tried this and while there is a little wiggle with some mags, others have no wiggle at all. I am talking a VERY minute amount, when it happens at all. With mags out I try lifting up on the ejector block and really do not see or feel any movement.

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    Really Senior Member AmEngRifles's Avatar
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    I have discovered (and should have known) that when I pull back on the cocking lever, everything is fine until I hit that last 2" of travel. Then the Striker Spring starts to really compress and causes quite a bit of resistance in that final bit of travel. Even with the gas port opened all the way, I suspect what is happening is the bolt is slowing and possibly just not making a clean recoil to the rear and it actually is short stroking on some cartridges.

    I think the designs of these semi autos generate added physical barriers that the original design parameters have problems overcoming. Not being a "hammer fired" weapon seems to be the biggest issue. I think it would have been a reliable conversion, if the original gun had been hammer fired. I believe all Striker Fired designs have this issue to some point. I have heard of problems with MG43 rebuilds (semi auto) and even the DSH RPD seems to have had problems in the past. They just don't receive the same "engineering" abilities that a large arms manufacturer can apply to get a design working properly and reliably.

    I own a Madsen LMG semi auto. It works with the crappiest of old surplus ammo. That is because except for the full auto modification to maintain semi auto ONLY functioning, it is still a hammer fired weapon and no new springs have been added to the design to operate a striker.

    So it would seem my solution may be to: A. open up the largest gas setting to over-gas the gun and drive the bolt back hard enough to overcome the striker spring in the system; B. find a spring of somewhat lesser spring force, that will compress easier, yet still have enough power to drive the striker home for a positive strike and cartridge ignition. or C. hand load really HOT ammo above and beyond military spec. That seems like the LEAST desirable choice.

    I am still open to suggestions.

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    Advisory Panel browningautorifle's Avatar
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    Quote Originally Posted by AmEngRifles View Post
    B. find a spring of somewhat lesser spring force, that will compress easier, yet still have enough power to drive the striker home for a positive strike and cartridge ignition
    I'd try this one first. I've hed things that gave similar issues and tried this to success... You can get springs wound by guys that do that and use smaller wire by number until you have success.
    Regards, Jim

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    Contributing Member Mr E's Avatar
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    It would be helpful to know what striker and spring system/version you have.
    My brens all have the pirate style setup and the maximum pull weight on the charging handle is 18 pounds with or with out the striker and spring using a fish scales.
    I would suggest looking to see if your striker is binding or getting tilted by the carrier and also see if you are getting coil bind on the spring
    Last edited by Mr E; 01-08-2019 at 03:48 PM.
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    Really Senior Member Brit plumber's Avatar
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    Is the body an original L4 or a .303 machined to L4 specs? I wonder if the body and inserts are machined to the correct dimensions.

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    Advisory Panel Brian Dick's Avatar
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    I think BP has it. My post sample L4A3 runs perfectly and I've never experienced any feeding issues with a variety of manufacture, original L4 magazines including ones manufactured in India.

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    Really Senior Member AmEngRifles's Avatar
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    Thanks guys, as usual, I left out some key details.

    It is an original L4A4 body. I will have to look again and determine where the welds are in remanufacturing. Some of these are better than others in that these "newish" center sections in the market, and that helps the builders hold better tolerances for some of the critical mid-ship dimensions.

    The mags being used are original L4 30 round magazines. That being said, I have not tried the indicator that Lee Enfield suggested, so will try that. Does this indicate a wandering tolerance that can be corrected? Silly question, all issues can be "corrected", one just has to know the source of the problem.

    btw, I tried 20 round L1A1 mags just for grins and giggles and they sucked. Every round on those would get jammed in a similar fashion, with feed horns ramming the cartridge just below the shoulder with the cartridge stuck half in and half out of the mag.
    Last edited by AmEngRifles; 01-08-2019 at 09:47 AM.

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    Contributing Member CINDERS's Avatar
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    A & C seem to be the least desireable options
    A) open up the port too much and your over gas could be very detrimental to the workings of the whole bolt carrier & piston group as once drilled out you cannot put it back.
    C) Goes without question as an absolute folly unless you want to wreck the LMG, yourself and bystanders they proof barrels/actions for a certian pressure for a reason.

    I'm wondering why P L has not imparted his practical experience and possible solutions to this quandry your having

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