I have a 5.45 x 39 upper that I'll be bringing to the Shootzenfest, as long as my plans don't change. Its a S&W M&P model.
I'm riding the fence anoput getting rid of it - I'm really Jones'ing for a suppressor, so something has got to give to make it happen... LOL
I'll certainly be glad to bring it up and let you try it out. I've got about 1500-1800 rounds of ammo, so if a Full Auto AR Lower shows up (and a F/A bolt carrier, mine's AR model), you're welcome to a few mag dumps to check it out..
PM me and we can discuss anything else that comes to mind.