Which lasts longer?  What is the life expectancy (round count) of the standard gas rings?

Additional input, etc. are welcome as well.

The McFarland spril gas ring is a solution searching for a problem.  Furthermore the ring is often so tight in the bolt carrier that it will induce stoppages.

Crack the receivers on your weapon and manually draw the bolt carrier almost out of the upper.  Return the charging handle to it's locked position and tip the muzzle down.  About 30° down muzzle the bolt carrier should slide forward on it's own weight and the bolt should lock closed.  Won't do it with excessively tight rings in there.

It has a benefit if you have an excessively worn bolt carrier or more likely one that was out of spec to begin with.  If the bolt will drop out of the bolt carrier by its weight alone the rings need to be replaced.  If it still drops out you're one of the few candidates for the MacFarland gas ring.

Your rifle will probably work with one (1) ring.  But I don't recommend you try it 'cuz the gas rings are one time use and if you remove them you need to fit new ones.

-- Chuck