Hi Shooter,

Seems like you're making no progress here. Tried different ammo, tried different magazines, cleaned it, lubed it, tried different lubricants and still isn't working consistently.

Only my opinion, at this point, call S&W and ask to speak to a tech that is familiar with this platform. There is something
definitely wrong with your rifle that no amount of "break-in" or
testing various measures is going to fix.

Your rifle should work with all ammo and magazines, as you have proved. It doesn't. So why frustrate yourself and try
to get to the "break-in" point if it doesn't work correctly?
At this point, no further amount of break in will correct it IMHO.

Clearly you have problems that are going to require new parts.
Why should you deal with it when its under warranty? In my case with my MP15 Sport 2, it started to short stroke. I cleaned it, lubed it, tried different mags, tried different ammo, with the same results. still jamming. Ran all the on-line tests.
My problem is in the gas system. I took the bolt from a buddy's Ruger AR556 and it ran great, no problems at all.

Now at this point I have a choice - send it back, or buy a new bolt at my expense. Why should I pay 80.00 (roughly) for a new bolt when S&W will fix it for free? Yes, I'm without it, and yes its a hassle to send it back (getting a ticket, printing it, boxing it up, taking it to Fedex, waiting to see if it gets there, waiting for results)

This is a quality rifle with a warranty, not a home built rifle from parts where anything can happen. IMHO save the frustration and aggravation and see what S&W will do for you.