80% AR9/AR40 - Glock 9mm Mag w/LRBHO - Finger Groove Front - AR15 Based Lower Receiver - 7075 - Anodized Black

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Anodized Type III Hardcoat - Finger Groove Front - 80% Dedicated GLOCK 9mm MAGAZINE with LRBHO AR15 LOWER RECEIVER - 7075-T6


Q - What does "Dedicated GLOCK 9mm MAGAZINE with LRBHO" mean?

A - Our lower is designed to accept Glock 9mm handgun magazines.  It includes an adjustable last round bolt hold open design (LRBHO) that works with all types of Glock Magazines and the LRBHO is adjustable. Also will function with .40 and .357 ammo.

Q - What is the difference between an AAO 80% lower and others?

A - Integrated Last Round Bolt Hold Open (LRBHO) - Our patent pending LRBHO is adjustable and it functions with all types of Glock Magazines 

   - Safe / Fire is laser etched into the AAO Lower.  

   - ALL AAO Lowers have a built in lower to upper adjustment feature that can be used to take up the slack/space between the upper/lower fitment (via an included allen head screw).  

   - You can quickly test your upper to lower fitment with the AAO Lower before you mill, this is due to a small pocket milled into the rear takedown pin area.

   - High quality and best in class precision machining for a good price.  We are real gun guys and we fire what we make, so it has to be good.  

Q - What material do you use?

A - All of our lowers are machined from: 7075-T6 Aluminum

Q - What is the finish of the lower?

A - Anodized Black - Type III Hardcoat

Q - What LRPK (LPK) will work?

A - We recommend the AAO MFG LRPK, however any standard mil-spec LRPK will work.

Q - How does your last round bolt hold open(LRBHO) / empty bolt hold open work?

A - Our patent pending LRBHO is built into the Lower Receiver.  It is reliable, adjustable and works with all of the various magazine types on the market.

Q - Do I need to adjust my LRBHO?

A - Out of the box the LRBHO is adjusted to work with Glock magazines.  See our video on how to adjust for other magazines.

Q - What magazines work in the AAO Lower?

A -Glock, Magpul, Promag and most all others.

Q - What bolt carrier will work with this S&W M&P Mag lower?

A - An AR-9 Bolt Carrier that has been cut to clear a Glock Magazine.  On the S&W lower , we also recommend further clearance of one edge.

Q - Do I need to use a special buffer for my AR-9 build?

A - We recommend using a carbine buffer with a spacer.  The spacer limits the travel of the bolt carrier so it doesn't break the bolt catch. 

Q - Should I adjust my Ejector?

A - We recommend verifying that your bolt cycles without excessive rubbing on the ejector. We also recommend using loctite on the ejector bolts.

Q - What does RAW or "IN THE WHITE" mean?

A - Raw means "unfinished" or "in the white", the unit has been fully deburred and is ready for you to finish.  

Q - What does "Finger Groove Front" mean?

A - Finger Groove Front means that the outside front side of the magazine well area has been machined with Finger Grooves in it.  We also offer a Flat Front machining option for the front side of the magazine well.

Q  - What information do you need if I choose CA Compliance Engraving via the drop down menus?

A - Leave your information in the notes section of the checkout page.

  • CA Compliance list information as follows: Your Name, Your City, State, Multi Cal, Your Serial# 
  • If ordering multiples lowers list your serial numbers as:  0001:0006 (serial number 0001 through 0006)

Q - Do you offer a bulk discount or other discounts?

A - Yes, purchase FIVE AAO Lowers and RECEIVE A 10% DISCOUNT on your lowers.

Q - What calibers can be built with this finished lower?

Glock 9mm, .40 and .357 (small frame)

Q - Is an FFL required to purchase this product?

A - NO, an FFL is NOT REQUIRED to purchase this product.

   - Anyone can legally purchase a 80% Lower Receiver.  An 80% Lower Receiver DOES NOT have to be sold through or registered through a dealer with a FFL (Federal Firearms License).   

Q - What JIG do you recommend to finish the AAO lower?

A - AAO Lowers are compatible with any JIG that will complete a standard Mil-Spec AR Lower.  If you are finishing an AAO 9mm Lower, the Ejector and LRBHO are removable so it can work with any standard Mil-Spec JIG.

Q - What are the operations that must be completed to make the 80% lower fully functional:

A - Machine the following using your JIG to finish our 80 percent AR15 Lower Receiver.  Our 80% Lower Receiver has a fully broached finished Mag Well.   

  • fire control group
  • safety select hole
  • trigger opening
  • trigger pin holes
  • hammer pin holes 
  • The AAO 80% Lower Receiver has been machined to match MIL-SPEC from a 7075 AR15 Lower Forging.

Q - What is a AR15 80% Lower Receiver?

A - 80% lower receivers are parts that have been partially completed.  

   - 80 percent or 80% is a generic term that means that everything is complete on the lower except for the fire control group, safety select, trigger opening, trigger pin holes & hammer pin holes.

   - Utilizing a jig and the right techniques, any 80 percent lower can be quickly transformed into a highly accurate and functional firearm. 

Q - Does a AR15 80% Lower Receiver require transfer or registration through an FFL? 

A - No. This is a do-it-yourself product.. You start with a 80% product and end up with a complete functional product after your finish the machining using your jig. 

Q - Is it legal to do this?  May I lawfully make a firearm for my own personal use, provided it is not being made for resale?

A - This quote is taken directly from the ATF Website http://www.atf.gov/files/firearms/industry/0501-firearms-top-10-qas.pdf: "Firearms may be lawfully made by persons who do not hold a manufacturer's license under the GCA (Gun Control Act) provided they are not for sale or distribution and the maker is not prohibited from receiving or possessing firearms."

Q - Can I build and then transfer a finished firearm to another individual? 

A - Yes you can, however you must mark the firearm in accordance with 27 CFR 472.92 (formally 178.92). You must follow all laws that are in place today. Do yourself a favor an protect yourself, don't put a completed firearm in anyone's hands unless you have gone through proper channels and background checks. Following the proper channels will protect us, our family, and our friends. For any firearm transfer it is your responsibility to understand the federal and local laws and how they apply.  

Q - Is it legal to assemble a firearm from commercially available parts kits that can be purchased via the internet or via Firearms News?

A - This quote is taken directly from the ATF Web Site: "Firearms may be lawfully made by persons who do not hold a manufacturer’s license under the GCA provided they are not for sale or distribution and the maker is not prohibited from receiving or possessing firearms. However, a person is prohibited from assembling a non-sporting semiautomatic rifle or shotgun from 10 or more imported parts, as set forth in regulations in 27 C.F.R. 478.39" https://www.atf.gov/file/61721/download 


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  • 5
    AR9 with LRBHO

    Posted by Giuseppe on Sep 8th 2020

    This is the first time milling an 80% lower. The quality of the lower is on point. Once it was completely milled and furnished, it resembled any other Mil-Spec AR lower. I would highly recommend AAO MFG to anyone.

  • 4
    80% at-9 lower

    Posted by Mick on Sep 1st 2020

    Good quality, lt shipped out fast

  • 5
    AR9 lower

    Posted by Josh on Sep 1st 2020

    beat all my expectations. Great product. Adjusting the LRBHO spring was simple and easy, took a little trial and error, but it works perfectly. Thanks

  • 5
    Great Product

    Posted by ShawnG on Aug 8th 2020

    Great finish, everything is to spec. GREAT customer service! LRBHO is the best!

  • 5
    Glock ar9 lower with lrbho

    Posted by Joshua Blair on Jun 15th 2020

    Hold open works as it should right out of the box. Finish was perfect and fit up was good with two different uppers. No need for tension screw although it is a great feature to have. Service was above and beyond! Looking forward to doing business with them again in the future.

  • 4

    Posted by Richard Shutter on May 27th 2020

    Lots of others out there do not compare in price! The uniqueness is the LRBHO function which one adjusted properly, functions perfectly fine. Compare that to others selling for twice as much! Can't beat these!

  • 5
    9mm lower receiver

    Posted by Charles Osborn on May 26th 2020

    Quality constructed 9mm lower receiver. I purchased the lrbho receiver, these are hard to find and at this price are an excellent buy. Would definitely buy again

  • 4

    Posted by Mike Boyd on May 14th 2020

    Looks great

  • 5
    Awesome lower

    Posted by David on May 13th 2020

    Loving it. Will be getting more. Thanks guys.