ATI Omni AR 15 Polymer Lower

    There have been many advances in polymer technology in recent years. These advances have been primarily in the area of accessories as far as AR15’s are concerned. ATI is moving ahead with a new major component for the AR15 constructed of polymer.The lower is called the “Omni” and is 100% made in the USA.


    Two types are available and they are a stripped lower and a complete lower that only needs to be attached to an upper of the shooters choice. When referring to a multi-caliber lower in the case of the “Omni” that would include .22 LR, .223/5.56 and .410 uppers.

    When recently introduced the price of the stripped lower was $43.95 with the complete lower for $134.95. The complete unit includes a GI type six position adjustable stock, buffer tube, buffer with spring, the polymer lower itself, trigger group as well as the fire selector, bolt release, magazine release and both takedown pins.


    As most of you know the lower is the gun as far as federal regulations are concerned and must be purchased through an FFL dealer. In the photos of the Omni you’ll note the serial number is a metal plate permanently mounted within the polymer just above the grip. This is a position different from most AR’s which have the serial number stamped into the metal on the left side of the magwell. Since the securely mounted serial number sits so far into the polymer it won’t fit within the magwell without interfering with magazine insertion and ejection.

    The “Omni” is mil-spec so any brand of AR 15 upper will fit. I used my CMMG AR upper in 5.56 for all range work. The upper and lower fit perfectly. In fact the two fit better than many all aluminum units. The only other AR upper and lower I’ve seen fit as well was on a S&W M&P AR. The front and rear takedown pins lined up with the upper without a problem. The fit is snug so taking a small punch or other non-marring tool would be handy on the range should you need to swap out uppers.


    Range Time:

    After taking the “Omni” out of the box I looked it over and then lubed it since it was bone dry. I used a fairly liberal amount of Slip EWL that got all the parts operating smoothly.

    I mated the CMMG upper and the “Omni” together and headed for the range. Most of you are aware that I normally shoot several hundred rounds when testing a new gun. I apologize for only firing 100 rounds of 5.56 and 100 rounds of .22 LR. Ammo is just that hard to find right now and I will have other guns for review in the near future.

    In any event this is not one of those cases where accuracy is of any consideration. Function of the rifle as a whole is the main consideration. I can say the function was perfect with 5.56 and the Federal .22 LR using a CMMG conversion.


    Essentially the only part of an AR lower that has any stress placed on it is the area where the buffer tube attaches to the Lower and just below that area. After shooting I checked that area with a USB scope at 40X and found no stress fractures or damage. I also checked the rest of the lower and found nothing unusual. I can honestly say that only extended testing over many hundreds of rounds would qualify as a complete test of the design in polymer. I can’t foresee any problems and expect it to last as long as most aluminum lowers. Only time and extended use will tell.

    The trigger in this lower example was good and proved to be a bit better than a GI trigger. The safety lever worked smoothly as did the mag release and bolt release. As I mentioned I did lube it and work the controls to get them broken in which didn’t take long at all.

    One thing about this combination I noticed right off the bat and that’s the weight. This lower weighs right at two pounds. The first time you shoulder your AR you notice the front of the AR just got heavier or rather it feels that way. This makes sense though since you just lost weight at the rear of the rifle with the lightweight polymer lower. I’m sure the user would become accustomed to this after a bit of shooting.

    After I noticed this difference I called a friend and asked him to bring out a CMMG dedicated .22 upper that is clean with no flashlights or any accessories at all. This felt much more natural in balance than the full 5.56 with accessories mounted.

    I also wanted to check several different types of magazines for ease of loading/ejecting and reliability. I had mags on hand from Magpul (PMag), several GI mags, CMMG .22 mags, Israeli steel mags and some old twenty round Colt mags. The only magazines I had difficulty with were the new Israeli steel mags. I can say that after seating them and ejecting a good number of times they also functioned fine. I can only figure that the new mags/lower needed a bit of breaking in. The PMags fit snuggly, which is nothing unusual. There were no problems with function.


    A combination of the ATI lower and a dedicated .22 upper would make a great combination. That will also give a .22 AR shooter a new rifle at a very low price. In my neck of the woods that would be a price of $470 for a complete AR. Now that’s a price that’s hard to beat!


    Over all I was pleased with the Omni. It functioned well with the upper receiver I had on hand as well as my friends .22 upper. The price is certainly right!

    I would encourage anyone buying the Omni to spend a small amount of time breaking it in with your magazines as well as working the controls after lubrication.

    As far as longevity that is something that only long-term use will answer. I still believe, with the low cost, this is a good alternative especially now with prices of standard AR parts and ammunition running at an all time high.



    Phil White

    Retired police officer with 30 years of service. Firearms instructor and SRU team member. I still instruct with local agencies. My daily carry pistol is the tried and true 1911. I’m retired as associate editor since December 14th 2017. My replacement is my friend Pete M email: [email protected] you can reach Pete for product reviews etc.