I understand that you want to use cheap & somewhat low pressure ammo, but the easiest things to do, aside from opening the gas port size some more, would be to try some genuine 5.56 pressure ammo with a carbine buffer, & with a reduced power recoil spring if you have it available.............it might work.
Obviously, it's not likely to work with the low pressure ammo though & as Yondering said, fixing the gas port size is the surest fix.
Unfortunately, there no book or pat set of conditions that anyone can recommend, just the directional changes discussed already.
This just might be a Bubba Project.............
MM
