Ran 3 more cycles through mags 7-11 ( I number my mags)......
The problem with feeding was being caused by too low a gas setting. Basically it's a timing issue. If you don't have the gas setting turned up high enough the bolt speed is reduced and it noses the bullets down into the mag rather than feeding them up into the chamber.
In any case, on setting 4 (type 3 block)...flawless. On setting 3....nose dived pretty regularly.
JFYI for those following along.
"Necessity is the plea for every infringement of human liberty. It is the argument of tyrants; the creed of slaves."-William Pitt the Younger