Semi Auto Bren extract problem

[Joe H]

If the striker spring came from another source then it may be too strong and is prematurely retarding the rearward movement of the internals. The recoil spring shown appears to be the standard outer spring or a Mk I. YAs you indicated... In many cases the gas port in the barrel and the largest orifice in the gas block were drilled over sized by Len to allow for more gas to drive the system. Adjust these holes conservatively and in small increments as once removed... metal is hard to put back. If Len did not build this gun I can understand why he is hesitant to try and address its current malfunctions- too many unknowns in its construction. Hope it works out for you.

Can't add much to what Wally said. Could be a combination of a too strong striker spring and a weak return spring. The MK I return spring? in the pic was replaced by a double spring in all Mks. I had an old MkI spring and had to replace it with the double spring. The semi's can be made to run on gas setting 3 or 4 but for best reliability the holes should be opened up since you are compressing an additional spring in the semi set up.

Looking back at your pics. the first thing i would question is the striker spring setup. Looks way too stiff. I've built semis with a striker spring in that location but it was much smaller and just slipped over the return rod , went back in the return rod hole and cocked the striker on the bolt return.

Thread on resizing gas system:

https://www.milsurps.com/showthread.php?t=45105

Good Luck

Joe