I have a DPMS 22LR (flattop) upper which I got to practice AR shooting. One thing I need to work on is using iron sights. Rear sights on the 22 upper are no problem: I just moved the carry handle from my Bushmaster. For the front, I ordered a "front sight for DPMS 1" bull barrels".  This has a 0.936" hole, and the 22 upper barrel has a diameter slightly over 1"  on my mike, but that was easy to solve: I had a local machine shop bore the sight out to 1.005" and got it on. More of a problem was that I neglected to order a front sight post (rookie mistake; I'm new at this). A little experimentation determined that a #8-32 flathead nylon machine screw would go in the sight post hole, and the screw slot pointing along the barrel gave something to sight with. I bore sighted this at home and took the rig to the range and finished sighting in by adjusting the nylon screw (to continue using the slot, this meant to the nearest half turn). Well, it gave a reasonable sight picture and, at 50 yards,  excellent accuracy (off a bipod) for me. The nylon screw is white, by the way. I have of course ordered a front sight post, but I have to say that the screw slot sight is not bad.

OP in OKC

I had same problem with mine. I took mine to camp perry and they exchanged it for one of the new m4 style 22lr uppers which has front site already on it. DPMS has great customer service.