I picked up a new ATI Omni AR15 polymer lower from by gun dealer yesterday, and I have some thoughts I want to share before I even head to the range. Above is a video of the unboxing and my initial observations and concerns. Below, I have more information and photos.
Mating an upper and lower has never been a problem for me – well, before now. I have several AR15 rifles in my safe and have access to dozens more at work. Regardless of manufacturer, I’ve always been able to swap uppers and lowers without any difficulty. This ATI Omni polymer lower is the first time I have ever run into any fitting problems.
I tried to attach a DelTon 5.56 upper to the ATI Omni lower, but I just could not get it to fit. If I attached the front and tried to pivot the rear of the upper into place, it would not get past the upper portion of the lower where the stock screws in. If I tried to align the upper starting at the rear, the front would not align properly. I could not get this upper to work with the ATI Omni lower.
I next attempted to mount a Rock River 5.56 upper to the Omni lower. This time I had a little more success. I was able to get both halves to align (mostly), but the rear takedown pin never would completely seat. I’m not certain, but I believe the measurements on the lower are a little on the small size, and the rear pin is angled ever-so-slightly to prevent it from going straight through.
Before I take this onto the range, I will have to solve this problem. I don’t plan on trying to shoot a rifle with one of the pins not properly seated.
If you watch the video, you will see me have two magazine-related problems with the lower: the mag well and the magazine release button. I tried multiple magazines with the ATI Omni lower: Brownells, Magpul, Tapco, EMA, Tango Down and some other generic metal mags. Some of them would not drop free, even when weighted down with loaded rounds. I suspect that with repeated use, the interior walls of the magazine well would wear down and the mags would all drop free.
The magazine release button would occasionally be extremely difficult to depress. You also see that on the video. I’m not sure on what may be causing that. Needless to say, it is an annoying issue.
The standard bolt release, like the magazine release button, is a bit tough to operate. Hitting it with your thumb isn’t always enough, and it sometimes takes multiple palm strikes to get the job done. Is this a problem of the upper and lower not matching perfectly? Maybe. I hope to figure it out.
Depending on my schedule, I hope to get to the range next week with the ATI Omni AR15 polymer lower. Maybe I can get a few of these problems worked out after a few hundred rounds of 5.56. We will definitely see!
Let me know your thoughts on what could be causing my problems, or if you have one of these receivers yourself.