L4 mag issues

[ActionYobbo]

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

Its simple really. He has no experience with striker fired semi auto rewelded brenguns that can be made with varying degrees of skill and use a multitude of new design components and pass no inspections.
Some of these builds run fantastic from day1 and others never ever run right. There is so many variables with these rewelds that need to be addressed and one of the last things needed is to drill th gas port. I have never opened up a gas port on any of my brens even the short barrel Mk3/1 and they all run on gas setting 2.

[browningautorifle]

Once they've been cut and welded back together, they're a different animal.

[AmEngRifles]

Thank you gentlemen. I will look for a spring maker first.

Mr. E, as to the questions on the system, I suspect it is a "pirate system". I am not familiar with that term, but the striker has a small skull imprinted exactly where the firing pin extension is struck, therefore, it has a nice shiny wear area. The striker is case colored. I suspect the stamped skull allows the maker to know approximately how much the gun has been fired? It is a HA build. I had been to see the maker, and it did not get fully resolved. Enough said. I have no binding of the striker. Now, I do not think the striker spring is binding, but hard to know once the gun is all closed up, ready for operation. Of course the resistance on the last two inches of cocking handle only increases in pressure, it does not feel like it bottoms out. And I do not think it increases pressure as it closes that 2", but feels more or less like a constant additional pressure?? I would opt to get a lighter weight spring, with enough compression designed into it so the coils do not come into a "compressed state", if that is possible? I will have to get a scale, but in my estimation, that final 2" of travel are well more than 18 lbs...

CINDERS, I am NOT talking anything wild in an uploaded cartridge. I have been reloading long enough to know that that pressure curves jumps VERY quickly at maximum. But also making sure I have consistency in pressure MIGHT help alleviate the issue, but I understand the pitfalls in that approach. I should NOT have said "load really HOT ammo, above mil spec"... With that said, wonder about a buffer system of rubber or poly, say about a 1/2" or 3/4" thickness, then trim or build a new striker spring with a corresponding shortened length to accommodate the buffer. I will say the spring thing seems like the best approach at this time. I may throw in a "buffer" system as well, or at least attempt it. Just gets complicated trying to re-engineer a new firing system for a modified (dare I SAY the words) automatic weapon.

And that last sentence alone is why I do not expect to hear from Mr. L. Not disappointed. I understand that completely. His expertise is with the original iteration. These ridiculous semi auto rebuilds in the US are not really his cup of tea. The original inquiry was related to whether L4 mags ever actually gave feeding issues in the full auto weapons. It appears as if they did not. No one has chimed in to say otherwise, so it removes the mag as being the problem. It is in the striker fired system.

One additional subject. Mr. E, thanks for that input on drilling out a gas block. I figured that was not the best approach, but my Mk III (Project Guns) has a faux Mk III barrel of correspondingly shorter length, and I had wondered if that shorter barrel needed a larger gas port, due to a somewhat shorter dwell time. Much like the issues with an XM177E1. I see the gas block as easily replaceable ( I have extras), but after your comments about all yours running on #2., I will leave that alone. Right now, both the L4 and Mk III still give me feeding problems on #4 setting. I think I have to play more with spring balance.

Has anyone ever tested the pressure needed to retract an original full auto Bren? Anybody know the resistance in lbs? I would guess it is more a less a constant force and well less than 18 lbs.

[ActionYobbo]

To check for spring bind just get the lower and holding the striker down push it to the rear until it engages the sear then it should still be able to move rearward aprox 1/8” give or take. If you are getting coil bind you will see it this way. Another test is to take out the striker spring and assemble the gun then stand the gun up virtucally barrel down. Pull back the charging handle slowly at first and feel for any binding. Ease the bolt and carrier forward release the striker and do the same test again but quickly. What the test is looking for is carrier & striker bind. You can also do this test with just the carrier and striker in the receiver with no lower.
18 pounds with or with out the striker sort of covers FA bren spring weight

Main striker designs are small diameter spring over original return rod. Large diameter spring over original return rod. Spring above return rod. There is the ML system but if you can see the spring its not the ultimate and fantastic ML setup
Ther was also a striker the had a portion the protruded under the carrier. It would help us help you if you could post a picture. As I always say a picture is worth a thousand guesses

[AmEngRifles]

Thanks Mr. E. Very helpful stuff. Will mess with it a bit and report back.

OK, did the tests you outlined. Drop test seemed to have no binding. Striker compression seemed acceptable. Take a look at the pic and see if that spring coil looks unduly compressed. Don't believe so.

Sometimes it takes me a while to grasp the obvious. But I left the striker spring out of the whole deal and assembled the rifle without it. NOW I know how a REAL L4 feels when cocking it. Smooth and even. Then upon reassembly, I pulled the cocking lever and realized once again, while not an extreme amount of additional spring pressure, it is there none the less. I included a picture showing at what point that additional spring pressure starts.

Also, while the striker spring was out, I ran a mag of only 6 rounds through the gun, to see if the ramming speed (bolt closing speed) was enough to give reliable feeding from the mag. It does. Although I tried it twice because the first time, it did skip the last round in the mag, which leads me back to the original question : Do the L4 mags springs ever get weak or cause misfeeds??

The gun would sure be a whole lot more reliable without that striker spring added in. But then it won't go "BANG!"

[ActionYobbo]

Your bren was built by historic arms. Its most likley already had the gas port opened up Len did that on all his brens.
Now I know its one of Len’s guns I would now be looking at the magazine to bolt clearance. See if the feed lips are reaching to the stops.

[Brit plumber]

A few questions,

Does the breech block have JI, 7.62mm, U or numbers on the side (if the side isn’t machined away for conversion).

Where the parts are rewelded back together, do the piston extension rails in the body look square and true?

Is the piston original or a compliant US made replacement, can you check dimensions against an original if new made.

What type of cylinder is installed?

What lubricant are you using on the guide rails?

I’m wondering if reducing friction in the guide rails and a better gas seal would help.

[AmEngRifles]

Brit plumber, the bolt is indeed marked as a 7.62. The receiver tracks have some uneven portions, as I suspect many rewelds do, but nothing binds as the piston extension ( bolt carrier) and striker move within the track smoothly and freely. I do believe the piston is a new, US compliant part. The gas cylinder is smooth under the bipod. Not sure if that means it is a type III or an original L4 cylinder? I have removed grease from inside receiver and gone to a light weapons oil.

Mr. E. Will look at mag to reinforcement stops but I have no knowledge of measuring those dimensions, so it will be a subjective observation. Mags lock in snug and there is little to no play in the mag release/ejector block.

Thank you all for the continued support and input.

[TactAdv]

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

I believe Peter has been busy as of late dealing with more pressing issues. I'm sure he'll pop in shortly.

[AmEngRifles]

After some helpful input from JoeH and others (thank you everyone), I am understanding the differences between the basic striker systems. I am also pretty impressed with what Mighty Lime has been doing, as he seems to have approached his solution with an engineering mind set. From what I have READ, his system seems to be the most reliable one, being the most balanced in all things based on engineering formulas.

I now believe that my L4A4 is just really experiencing short stroking, so that the bolt is really not coming back in full travel, thus giving me a bolt over base misfeed. I have a similar issue with a Project Guns MkIII. The issues ( as applied to many guns, not just mine) seem to start up from with the gas spigot, and compound themselves as we move rearward in the gun, through the gas piston, and it's diameter and length and even whether the piston face is cupped (as in one builders design) or just better fitted with the standard flat face. NEW, better fitting gas pistons are one of the easiest parts to make and replace in that train of integrated (gas) parts. Would be nice to see someone produce a variety of gas pistons to be sold, so one could tighten up their bleeding gas system.

Then comes the bolt carrier modification (which seems ok across the board as far as NOT causing any issues) and the striker itself. Mighty Lime states some very good reasoning for having the lightest striker possible, but with the duties of the striker, it still becomes a massive chunk of unnecessary weight. It has to have rails to keep it guided while traveling inside the receiver guide slots, a capture hole (meaning length) to allow spring or recoil rod to pass into and thru and a sear cut to catch and be held by the sear during the firing process. All the extra weight complicates the math in figuring spring forces to have reliable cycling. ML striker always struck me as an elegant shape, but now I understand why. He simply was reducing mass to the design. Could these be made out of Titanium, or would that be cost prohibitive? Does Titanium not stand up to battering?

But the Mighty Lime solution goes beyond just slimming down the striker. He also elegantly contains the necessary drive spring and support parts to a minimum to reduce that force needed to cock and operate the striker.

I am very interested in converting my L4A4 into a Mighty Lime set up, but he does not offer this as a service. I have only just been introduced to the Builder's Guild and those guys are WAY smarter and more talented than myself. I am just a trigger puller. Would be nice if someone would start retro fitting the "other" designs, with the ML design (maybe even as a drop in kit?). I do not think anything that is required in the ML design is not doable as the other designs should have unaltered recoil tubes and the ability to accept his modifications. The modified recoil tube and an additional striker spring tube is required as I understand it. New design specific strikers would be required as well.

I will be hanging out at the Builders Guild a bit more, trying to absorb as much as I can. Thank you to all who have helped me with this journey. I WILL get my problems resolved and I WILL love these Bren guns that I have always wanted. I just am disappointed that they do not come as reliable as they could have been, from the get go. As much as they cost, I expected more.