Update.
Ran the L4 yesterday at the range. Ran on #3 gas setting with zero issues. I was pleasantly surprised. Ran 10 round out of two mags, with no last round jamming issues. Rand 20 out of each of two mags with no last round feed issues. Ran that twice. Not sure what changed? I did try gas setting #2 since everything was going well. Had a couple of bolt over base jams, so went back to gas setting 3. All this seems to have come about with the removal of the INNER recoil spring in the butt. The previous range trip had last round jam issues, but those seem to have improved?? Have no idea what was different? Happy as a peach since I still have ONE whole gas setting left as reserve.
At some point, I will try clipping a striker recoil spring and see if I can get the system to operate on gas setting #2? Not imperative, but would be nice to run one lower setting again. Mainly as there is diminished recoil when running on gas setting #2. Since the HA Brens no longer have the working buffer in the back end, nice to reduce some of the banging going on internally.
I will also get set up with a improved spring system as per Joe H. I am half way there. Just need to locate the spacer for the recoil spring tube. Hoping this is basically resolved and much of it seems to be getting that balance of spring rates, which everyone knows or discovers as the BIG issue with these semi auto conversions. I am now looking for a rubber or plastic spacers, both for the recoil tube and one to go inside the striker spring on the original HA system. Will report on the success of such at a future date. Having option is always good.
Will see how the mags do over the course of the next several range trips. Not sure why they would have issues on one trip and then no problem the next? Got tape ID and records for each mag for functioning now to get a running history.