Semi Auto Bren extract problem

[scoobsean]

I would use the striker spring that you have. It looks good from your photos. My gun came with a worn striker spring that was crushed in a few places. It did not have enough power to push the striker hard enough and I was getting light primer strikes. If you put in a softer spring you might also have light primer strikes too. Only change one thing at a time.

[HENRY B]

how many of us have gone down this same path ? lots of $ and end up with a non working gun. schnellfeuer and mp44 neither would work without a lot of swapping parts. i feel your pain,both from gun broker

[WallyG.]

Depending on how well the builder copied the Historic Arms design... the new bolt carrier will require significant machine work to convert it to the semi auto version. Eliminating the binding issue might just solve your problem... what parts are binding and where?

[Joe H]

Only change one thing at a time.

locchau,

Take Scoobsean's advice : fix one thing at a time, locate and solve the binding problem. I'm having a hard time imagining what would be wrong with the bolt carrier that would need replacement.

Whatever the problem with the tube or carrier, get it fixed first then try it out. That may be the only problem. If not decide where to go next.

I never realized there was a height difference in the regulators. As far as I know all the MK regulators are interchangeable.

As far as the regulator, I used regular HSS drill bits. HSS will work on the barrel hole and exit hole. The regulator is very hard. If you are only doing one hole you may try a carbide drill bit. It has to be lined up properly. Working with small tooling in hard material is always a problem, you break one or two bits before you learn the right technique. Don't mess with the gas system if you don't have to. Consult your machine shop friend before you do any drilling.

Joe

[locchau]

Scoobsean,

I’ll take your advised and leave the striker spring alone. Right now I just concentrate on fixing the binding problem, and finding way to drill the gas regulator hole. Look like there still lots of work ahead to get this gun to run. Henry B, thank you for your honest commend. This is my first time that I get a none working gun for lots of money and consider myself lucky since the problem seem fixable. My only complaint is that one ought to be honest to stated the working condition of thing they sale, especially something that liability related. Again, thank you all for your help and hopefully I can get this gun to run soon.

Loc Chau

[Peter Laidler]

More great advice from single-shot Bren maestro Joe. Just fix one problem at a time, working your way forwards until you get to the end. That way as you move on, you know you have eliminated all the previous problems

[locchau]

Joe, Wally and Peter,
From my machinist friend, the problem is from the tube and not by much. Drilling the Regulator port may fix it. I attached 3 pictures; one with my finger pointing is where the piston started to touch the gas tube, the second picture is when I press the carrier toward me the binding goes away and third is where the full auto blocking welded (total 4 welded). The carrier milled flat on the side that have the full auto blocking weld and my friend thinks that with a new carrier, he can mill it and leave off a little metal just enough to push the carrier and piston to one side and that eliminate the binding problem. What do you think? My though is that with the gas regulator holes drill may just be enough to pull the piston back far enough for the empty case to come out. If I lean the receiver from one side to the other, the carrier slide in and out easily so the bind is not that bad but with all the springs install it may get worse. Thank you all for taking the time to help me with my problem.

Loc Chau

[Joe H]

Loc Chau,

Two points to remember

1- the carrier& piston are as from the factory. In this design the tabs that engaged the receiver body were milled off. There is probably nothing wrong with this part. Any further machining on this part or a new one is probably going to unnecessarily add slop to the carrier -receiver fit.

2- The receiver was torch cut in at least 3 places removing a minimum of 1/4" of steel at each location so that it could be imported to the US as scrap metal.

The carrier was milled in a milling machine. The receiver was welded up by the guy who sold you the gun. Which one is probably screwed up???

My Opinion -- Eliminate the bind by grinding the inside of the receiver (dremel, die grinder, air pencil grinder), only where its binding. Don't depend on the gas system to do job the builder should have done.

Here is the test. Using only the receiver, carrier w/piston and the bolt no springs , striker, lower trigger frame, hold horizontal then rotate vertical. The bolt & carrier should slide totally forward and the bolt should lock up with the locking shoulder. No springs, no finger pushing or screwing around. If it doesn't there is a problem.

Below is your pic lightened up. Your pointer is right where there is quite a bit of welding.


My 2 cents,

Joe

[Peter Laidler]

Also worth remembering here is that the piston MUST articulate on the piston extension. It is made this way. There MUST be some movement between the two. The criteria for this articulation was that when the gun is assembled, the piston should not foul with the body as it enters the gas cylinder which is tapered inwards to allow for a smooth entry.

[Sentryduty]

Also worth remembering here is that the piston MUST articulate on the piston extension. It is made this way. There MUST be some movement between the two.

This still holds true with the FN MAG 58/C6/M240B series even today, curiously the FN Minimi/C9/M249 uses a totally rigid piston and somewhat sloppy fit in the sheetmetal gastube.