The Dirty Bird AR-9 Billet Receiver Set + SRMS Handguard, also known as a “9MM Builder Set” is an outstanding way to start your build. This upper & lower receiver set is manufactured to work perfectly together. Zero shortcuts were taken. You can expect clean machining, excellent fitment and one of the most reliable last round bolt hold open systems on the market. Read more below:
Dirty Bird DB9 9mm Billet Lower Receiver
The DB9 Billet Lower Receiver is an ideal choice for starting your pistol caliber (9mm, 40 S&W, .357 Sig) AR build. Precision machined from a solid block of 7075-T6 billet aluminum and finished with hard-coat black anodizing per Mil 8625 Type 3 Class 2 specifications, you can be sure that this unit is as tough as they come.
This lower receiver accepts any Glock style small frame pistol caliber magazines in 9mm, .40 S&W, .357 SIG, etc. and the mag well features a beveled feed lip for quick and easy mag swaps. Extensive testing and attention to detail also ensure that your Glock style magazines will drop free when released. The proprietary magazine catch and ejector is included and pre-installed from the factory.
Other features include:
- Threaded takedown pin spring and detent hole for easy installation. Set screw is included. Note: To prevent excess pressure on the rear takedown pin and detent, you can shorten the detent spring by the same length of the set screw using some wire cutters prior to installation.
- Threaded upper tension screw to adjust any “slop” out of vertical fit between the upper and lower.
- Ambidextrous finger rests above and below the mag release.
- Threaded bolt catch pin included for easy bolt catch installation.
- Lifetime Limited Warranty
This lower will drop-free factory Glock small frame pistol magazines. It has also been thoroughly tested with Magpul GL17 9mm pistol magazines to fit and drop-free. Promo, KCI, Kahn and other types of magazines will also work but due to varying thicknesses relative to factory Glock mag dimensions, slight modification may be required.
Last Round Bolt Hold-Open
After evaluating many different design concepts from other manufacturers and finding fault in nearly all of them, we’ve designed this lower to use any standard mil-spec or similar bolt catch. Our last round bolt hold open technology instead resides in our matching pistol caliber upper receivers. These billet upper receivers use a PATENT PENDING design which has been proven in numerous field tests to provide the most reliable last round bolt hold open of any that we’ve tested.
Bolt Carrier Group (BCG) Requirements
You’ll need a BCG which is compatible with Glock style magazines. Some BCGs in the market are compatible with both Colt and Glock style magazines but some others are specific. The difference is Glock magazine compatible BCGs have the relief cuts necessary to clear the magazines.
Lower Parts Kit Compatibility
Any mil-spec or better LPK will work but you won’t need the mag catch assembly, bolt catch roll pin or the trigger guard as those are all included with this lower.
You’ll want to use a 9mm (extended) buffer which is longer and heavier than a standard carbine buffer. Standard carbine buffers will work but it’s a good idea to use a spacer to limit the rearward travel. This is simply because a 9mm BCG is shorter than a standard BCG which means there is more travel and gives the BCG more time to build speed as it returns home and this extra velocity can cause excess stress on the bolt catch. 9mm extended buffers are common and well worth the investment.
Before firing your new build we suggest you adjust the ejector. You can do this quickly and easily by following these steps:
- Back-off the two hex-head screws holding the ejector just enough so the ejector has a semi-tight “friction fit”.
- Ensure the ejector is seated all the way to the rear and all the way down in it’s pocket.
- Close the upper onto the lower with the bolt all the way forward.
- SLOWLY cycle the bolt in and out about 1/4 of the way back a few times.
- Allow the bolt to close all the way and tighten up the ejector screws. No need to over-torque as this could cause the ejector to shift position, we’ll be adding blue (non-permanent) locktite in the next step.
- OPTIONAL: At this point you can use some dummy rounds to check for proper ejection.
- Remove one ejector screw at a time (ensuring the ejector does not move) and add a dab of blue locktite to the threads and tighten them back down.
New Frontier Armory Pistol Caliber Billet AR-9/45 Slick Side Upper with LRBHO PATENT PENDING
Caliber: Multi (will accept any barrels, bolts and caliber designed for the AR-9/45 style platform)
Weight: 8.96 oz
Measurements: 7.662 x 1.375 x 2.314
Other Specifications and Features of the Billet AR-9/45 Slick Side Upper with LRBHO:
- Machined from 7075 T6 aircraft grade billet aluminum
- Matte black hard-coat anodized per Mil 8625 Type 3 Class 2
- Compatible with all standard AR-15 / AR-9 components and most aftermarket parts
- Manufactured to MILSPEC on state of the art CNC equipment for consistent quality parts and exacting tolerances
- Save money by building your own AR-9 rifle or pistol from the ground up exactly the way you want it configured
- Designed to match lines with New Frontier Armory C-9 & C-45 Billet Lower
- Contains integrated Last Round Bolt Hold Open (LRBHO) technology (PATENT PENDING) that reliably holds the bolt open when magazine is empty
- LRBHO feature is designed for lowers that accept Glock style magazines
- **NOTE This upper is not machined for a gas tube as it is intended for blowback gas systems only
Once assembled the small hook end of the wire form in the upper should be pushed up by the follower of an empty Glock magazine which will engage the bolt catch on the last round fired to hold the bolt in the locked position. If it does not engage, or engages before the last round is fired you can make VERY SMALL adjustments by SLIGHTLY bending the hook end down to lock faster or up to lock slower. They are set and function checked during assembly with brand new Glock magazines and our standard bolt catches. Because of varying magazine specs, magazine specs changing over the life of the product, different thicknesses of the pad on the bolt catch and other variables, this adjustment may be necessary with your specific parts.
**NOTE: Some rail systems that use anti-rotation tabs may need slight modification to fit this upper. It is designed for flush mounting rails and standard hand guards.
The New Frontier Armory Pistol Caliber Billet AR-9/45 Slick Side Upper with LRBHO is proudly MADE IN THE USA by hard working American men and women.
Dirty Bird Industries SMRS (Slim M-LOK Rail System) Handguard:
- Machined from aircraft grade 6061-T6 aluminum extrusions.
- Anti-rotation tabs.
- M-LOK attachment slots on all sides (except top)
- 1913 Picatinny top rail with shaved and beveled center section.
- Raised QD attachment points at the 3 and 9 o’clock positions.
- Snag free design with smooth, uniform octagonal surface ideal for accessory attachment or application of specialty coatings or patterns.
- Aircraft Grade aluminum barrel nut. In our tests, the aluminum barrel nuts are just as effective when torqued to spec. Additionally, the weight savings enable us to utilize a longer barrel nut design which means more surface area at the attachment point without adding unnecessary weight.
- Compatible with most known low profile gas blocks.
Straight Forward Installation
- No frills clamp-on style installation using only a 1-3/16 Crow’s Foot wrench and 5/32″ Allen key.
- Barrel nut does not requiring timing with the gas tube. No shims required.
The end result is a great looking, zero compromise handguard suitable for a wide variety of builds.
1.7″ Maximum Vertical ID (for considering vertical height of gas blocks