IMHO I would rather shoot ammo that maybe doesn't group quite as well than have a OBD and have to send my rifle back to S&W. I know maybe it isn't all the ammo's fault but why press your luck.

It is my opinion that maybe a OBD could be caused by an accumulatiion of burnt powder residue on the bold face recess where the shell is held by the bolt or a accumulation of same residue/gunk in the breech end of the barrel notch where the extractor rests when the bold is in full battery. Also any binding of the bolt on the slides due to lack of lube and gunk could cause this also. The loading ramp seems to build up a lot also so I always take a cleaning kit anytime I am going to fire over 200 continuous rounds and give the rifle a quick cleaning/lube before firing another string. Some .22 rimfire ammo is really pretty dirty and may add to the buildup faster than other ammo. I know this is a pain in the ___ but so far it has worked for me.

This little MP 15-22 is a fine tuned rifle and more prone to such problems than a full sized AR which is not quite as fussy on the cleaning thing. Not saying I am right on any of this theory but maybe any of these conditions could hold the bolt open enought to cause a OBD. Just my 2cents worth.