Hope no one minds bumping an old thread. I am about to put the Poly Forward APEX kit in my CORE, and got a 1.27mm wrench as mentioned above. I find it has slop, and am now going to buy a 1.3mm used by hobbyists.

I'll report back if this is a better fit.

By the way, is the trigger all you hoped it would be?

I shoot the M&P in USPSA comps, and then use a SW1911PC 45 Bobtail for IDPA. It's hard when using the M&P because I catch myself thinking there's a problem when the break is so far back.