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 the Associate Editor and moderator at TFB. I really enjoy answering readers questions and comments. We can all learn from each other about our favorite hobby!


  • TangledThorns

    If you put the Magpul brand on a polymer lower it’d probably outsell aluminum lowers.

    • shit, put their name on a lower and pump them out for 100 bucks and they would be gone before they were even on shelves…

    • Schizuki

      That’s a great insight. You’re right. When I hear “polymer lower”, my first thought is “Ugh, Carbon-15”. But if it was Magpul, I wouldn’t hesitate.

  • Esh325

    I didn’t read the whole review. I do believe polymer lowers and or uppers will be next big innovation with AR15’s in the near future. Past examples might have failed, but polymer and manufacturing techniques improve with time. We must remember that Aluminum Alloy in firearms was not perfect out of the box either when it was introduced.

    • me ohmy

      no but FAIRCHILD was making AEROSPACE TECH and they addressed most of these issues with Gene Stoner and his brilliance, love or hate Him and His Mouse Caliber Poodle shooter, it was revolutionary, and has been our longest and best tested rifle system ever in the US Arsenal.

      • Esh325

        Uhh… Okay?

    • very true and I know that they will be successful in the long run if not already with the ATI.

      • Tuulos

        Actually there already is the Cav-15 lower which is very durable so I’d say polymer lowers have already been made successfully. Gwacs Armory LLC is the current manufacturer of them.

  • Weapon Builder

    Hope it holds up better in cold climates than my Plum Crazy did! Just 11pm tonight my rifle slipped off the trunk of my toyota, fell ~3ft and broke apart. I heard the cold can make some guns more brittle, but this is the first I’ve seen of it. Also broke the polymer fab defense light mount.

    • interwebs762

      Wow that is crazy! I have a New Frontier Armory lower. I am very pleased with it though I don’t do anything more strenuous than trip to the range with it 😀 How cold was it when this happened to you?

    • You know I haven’t heard as much from them lately

      • Phil

        I’m in Canada and have had my ATIs out a number of times and no issues. They take the cold better than I do!? We have several hundred sold in Canada and no issues so far. He is right they are a snug fit together the first 20-30 times and then they will press together and light tap apart. About the same as a fresh Accu-Wedge in an aluminium set. Good luck we have had great success so far.

  • travisd

    Sorry, running only 100 rounds through a gun, especially one with a polymer lower, is not a valid test.

    Why is it called “American Tactical Imports” if it’s made in Rochester? Makes no sense.

    • they import as well as have in house projects

    • I know 100 rounds is not a valid test and I did say that along with my apologies for not having more ammo to use. Usually I do fire a minimum of 300 to 400 rounds.

    • Nadnerbus

      Think of it as a product introduction and initial impressions. He made pretty clear the limitations of his testing in the article.

      Also, if he did get funding from gun manufacturers to pump a thousand rounds through the rifle, people here would be jumping down his throat as a corporate shill for the gun industry. He can’t win either way, so I’ll take this kind of review, thank you.

      • Thank you I do appreciate your clear views. Sometimes you can’t win:-) Really you can’t let anything like that bother you especially if you know you’ve done your best and been honest about the product.
        One thing many readers don’t realize is that none of us get free or even discounted ammo for reviews.Come to think of it I did get some free ammo one time a couple of years ago but that’s it. All of the ammo cost comes out of my pocket. The same for all the other writers.

    • interwebs762

      Ammo is not very cheap right now…

      • The 500 rounds I got this Friday after standing in line two hours and taking a number cost $370. Still a better price than many are charging these days.

    • Ive put about 1k rds through my polymer lower with no problems

    • travisd

      No apologies needed, I realize ammo is hard to come by, and I guess that came off more dickish than I intended, sorry about that. I appreciate the review, I know the Canadian dealer for this lower quite well and he was showing it to me a few months back.

      I guess I saw the low round count as being an elephant in the room.

      • I appreciate that sir. I finally found some 5.56 Friday so I’m good for a couple of reviews. By then I should find more. No casual range trips for me right now—gotta save it for reviews:-) I actually hate doing low round count reviews even if the part doesn’t really effect accuracy as long as the fit is snug.

        Hopefully things will get back to normal before to long!

        • Phil

          Thanks to Travis, we are the Canadian importer and we have three guns at decent round counts, one is about 7000, another at about 5000 and a third at about 2000 and all are going fine. The high round count gun actually spent some time in a range program and got shot A LOT and was the best rental while it was there. I noticed the magazine well tight on a few as mentioned and we had one with an NS bolt catch but that wasn’t the lower’s problem. As far as the “MilSpec” reference, I used to work with true MilSpec M16s and I have found in my measurements of the ATI lower that the trigger pin location and the pivot/takedown pin locations are well within Mil Spec. It might not be select fire and all that but it fits a BAD lever, ambi safeties, al the mags I can find and works. We only had one upper not fit and that was machined wrong when I checked it on my bench. (The eccentric on the takedown pin wasn’t machined and when that was corrected, together it went.) We keep shooting them and they keep impressing us. Especially at $199 retail up here. (Love your prices but we can’t match them and legally import everything.) Still with a decent High Standard or HeadDown upper half it gives a quality 5.56 AR for under $1000 Canadian that really shoots. Hard to beat.

  • -V-

    I too am interested to see how this one manages to hold up. The known stress points are the front takedown pin and the neck where the buffer tube screws in. I think most people who have had failures have usually had them around the takedown pin holes.

  • me ohmy

    still don’t put much credence on calling a civilian anything “MILSPEC”, since there is no MILSPEC for a polymer lower. the term is severely misused, MILSPEC means it is made of a certain material, to a certain required strength, a composition of correct stated contents, and has the standardized and MILITARY SPECIFICATIONS as written in the MILITARY NSN number for it to be a perfect match and as well made as it needs to be to FIT MILSPEC category.
    MILSPEC is almost the same as an ISO 9001,with stated ability to make the products as required and now recognized as “good enough”.

    also, the whole REAR BUFFER TUBE BRIDGE area isn’t at the same tensile strength level of ALLOY 7071 with a T-6 heat treat standard lower. these WILL fail first in that buttress area, for the simple reason of the plastic specs are much different then just reverse engineering a standard lower. the price point is nice, but not if it fails at 1000 rounds of abuse testing.

  • CavArms used to make a damn good lower but they were A2 stocks molded directly into the lower. I never had a single problem with mine.

    • The Cav-15 is back in production under a new owner, but they’ve jacked up the price and it’s no longer available in the huge range of colors it used to be.

      • I so desperately want one of the MK3 lowers they were making right before the SHTF at CavArms.

    • D

      Mine is A1 length, as seems to be the consensus…

  • Hami

    I found the “finish” on my Omni lower to be of a much higher quality than my New Frontier lower. The polymer feels smoother to the touch and debris wipe off easier.

  • tincankilla

    Can you explain why “this is not one of those cases where accuracy is of any consideration”? Are you intending to say that the lower is just accurate as aluminum? Or that you don’t care about accuracy?

    If this is touted as an alternative for aluminum, why isn’t accuracy being considered?

    • Duray

      Because slapping on a random upper and measuring the groups you get isn’t going to tell you anything about the quality of the lower. It’d be like doing a review of a new pistol grip and judging it by what size groups you get. It’s silly.

      • tincankilla

        Ah, got it. And I get that a lower shouldn’t have much impact on accuracy. But he’s got his standard lower in his range bag, so at least we’d have some point of comparison.

        • The reasons others gave pretty much covers it especially the new grip making a change in group size. It’s just not relavent.
          If it helps I shot both from the same distance so nothing to write home about in the way of accuracy difference.

        • Actually the Omni lower fits my upper better than the factory upper. Very good fit all around.

      • Cords

        2nd ATI lower just broke above the take down pin I do not think polymer has enough strength to hold up especially in the cold weather

    • lolinski

      What does the lower have to do with accuracy(exept the trigger)?

    • A330

      I wonder what Frog Lube will do on a polymer lower?

      • Nothing at all. It’s a neutral combination of botanicals. In fact the owner uses it as lip balm—seriously!

      • If you mean does it work on polymer yes it does. I also used Frog Lube on this one today after cleaning all the old lube out.

  • Nathaniel

    That carbon reinforced polymer reminds me of AR-180B lowers.

  • Nadnerbus

    Wow, for the MSRP of a stripped lower, even if they prove to be less than rugged, its kind of hard to go wrong with them for a range gun. I would love to be able to get my hands on a couple for testing out. But, California.

    • Cymond

      I don’t know anything about the Omni, but I bought a New Frontier polymer lower a year ago in the Bay area. I don’t see how California is a real problem, unless the current proposals pass.

      • Nadnerbus

        I know they are currently legal, it’s just that, between the national buying panic and California Democrats’ announcement two days ago that they plan on banning all detachable magazine auto loaders as well as all “bullet button” type kits, I am skeptical I will ever get the chance to buy one here. By the time the supply chain gets back to normal, I have a feeling that the state government will have passed at least some sort of legislation to make them unobtainable. Hope I am wrong, and the proposed legislation all sounds quite unconstitutional, but that has never stopped them before.

        • I’ve heard all about that. I have a friend who is a range instructor and plans on moving—he’s had all he can handle.

    • Bought my plum crazy lower in cali

  • I found with my plum crazy lower they was zero movement between the upper and lower and the trigger was a lot better then my mil spec on my aluminum lowers.

  • RickH

    I have no issues with plastic receivers. But I would think they wouldn’t have to keep the dimensions exactly like the alloy receivers. The critical internal dimensions for all components have to be retained, but why not “beef” up the areas that need it?

  • Laserbait

    Heh – just don’t expect this to hold up with a 458 Socom, or 50 Beowulf on top of it. I have broke a CavArms with my Beowulf, and a buddies Plum Crazy broke on the 1st shot with a Socom.

    • The review repeated the ATI cautionary statement of .22, 5.56 and 410–that’s all that can be used in this particular lower.

      • Justice

        Phil, I have shot 2 mags (60 rounds) of 300Blackout through my ATI complete lower mated with a PSA 300BLK upper with no issues. Just like you, I was not able to find anymore 300BLK ammo due to the shortage.
        I think it would work just fine with casual use on the 300BLK cartridge for an extended period. I’m not sure if I want to put it through anything more rigorous than my casual range shoot.

  • birda40

    I have a plumbcrazy lower, the trigger is the best of all the lowers I have. I used a sling hooked to the back of the lower, it put to much stress on the rear pin, it just turned to powder from the weight. It is an easy fix but it is a weak point. I use it for a 5.7×28 upper. Not sure if I would use any thing larger.

  • JoelsChaos

    Ive had a Plum lower for years with zero issues. About 2.5k rounds of 7.62×39 and 1k rounds of 5.56. Slammed the buttstock a couple of times and used it in the desert and snow. Only mod ive done was drop in a rra trigger over xmas.

  • raybo

    ray a. here. my nephew purchased an ati ar 15 a few months back we were
    shooting last night and the entirerear of the ar broke off in my hand. crack ran all around the buffer tube to the rear disconnect pin. polymer upper and lower. ammo sensitive? disconnect pin flew out of the receiver hole. yes it was seated prior to discharge.i really dont appreciate a design flaw that would cause a catostrophic failure like that. 350 rounds fired lubed well
    i spent 15 years as a tank commander/tank platoon sgt. and have actual shootat/get shot at time from .22 to 120mm smoothbore i am not new to firearms or the culture of being armed i me pissed my nephews safety was put in jeoprady by this rifle any one had a similar experience

  • stevor

    I have an ATI Omni lower and need to put a bullet button on it since I’m in Kalifornia and the bullet buttons that I have don’t push in very far, sticking out quite a bit. Has anybody encountered that? If so, how was it dealt with?

  • Justin

    I ha e so many questions. I will be buying my first AR-15 soon and was looking af the ATI omni as my choice, but have heard that the polymer lower by the buffer tube will crack ans some times broke. If anyone has some input email me.

  • Lance Akovenko

    So, what’s the current word on ATI? I have, what I believe to be is the
    GEN 1 Omni, on hold for me right now pending my NICS. I saw it at the
    MPLS gun show today for $500! I him’d and haw’d for about 30 minutes
    and then finally told the dealer I would take it. For my 1st AR, is
    this going to be worth the $$$???

  • Lance Akovenko

    So, what’s the current word on ATI? I have, what I believe to be is the
    GEN 1 Omni, on hold for me right now pending my NICS. I saw it at the
    MPLS gun show today for $500! I him’d and haw’d for about 30 minutes
    and then finally told the dealer I would take it. For my 1st AR, is
    this going to be worth the $$$???