Matador Arms Mat-9K / Brownells BRN-9 Upper

[CoffeeFreak]

Matador Arms Mat-9K / Brownells BRN-9 Upper




A little back story.​

I have this love-hate relationship with the AR-9 platform. I have quite few and with the price of ammo, I put more rounds down range with this platform then almost anything now a days. I ran across Gunvira’s video on the BRN-9 a couple months ago and started researching it. I always loved the PDW and back pack gun concept but I really don’t want to register another SBR. An inexpensive monolithic bufferless AR upper that let me use a SBR lower I already had was extremely tempting, even though I have two other AR-9s and a couple other AR-9 uppers. To my dismay, Brownells discontinued the BRN-9. I’m going to tell you why I think they did that later on. The good news was, Matador Arms, the manufacturer who made the BRN-9 for Brownells was taking pre-orders for an improved version of the same upper now released called the Mat-9K. I pre-ordered one a few days before release and it came in $100 cheaper then Brownells sold them for plus I got 15% off via a discount code a friend gave me. A cool $424.00. Considering, that’s the entire upper, bolt carrier, recoil spring assembly, all ready to run without all the additional buffers, springs, tuning and testing I’ve had to do with other builds, I think it’s an exceptional value.

The good​

The upper is a really good design and very well made. It dropped right on my Anderson Arms SBR lower I used for my 22 upper without anything special having to be done. HB Industries is developing improved accessories for it. The same quality accessories they make for the B&T APC-9 and the Stribog. The folding charging handle and locking charging block they sell I put in my Mat-9K. The A-3 Tactical grip is awesome but buy the B&T only model for the APC-9K. The one I purchased required modification to use that the B&T only model wouldn’t. Recoil is actually very good. Much better then I expected. Not MP5 or Banshee good, but CZ Scorpion good. The weight is two pounds lighter then my New Frontier Armory C-9 AR SBR and is 30% thinner making it an awesome backpack gun. I have seen YouTube videos show it works well with binary triggers if that’s your flavor. It works with Mean Arms Endo mags and probably the new Exo mags.

The not so good​

This upper is being marketed as compatible with most 9MM AR lowers and mag-well adapters. It’s supposed to work with Colt, MP5, Scorpion, Glock and Sig mags as well as Mean Arms Endo Mags. I agree, it is probably compatible with most 9MM AR lowers, but the only mag-well adapters I can see this working with reliably, without modification is the Glock and Sig adapters Matador sells. I can make it work with other mag adapters but it requires making a new ejector. Most Glock mag adapters, Stern Defense and Sylvan arms are two that I have, have their ejectors just behind the magazine and are designed to work with Mil-Spec AR ejection ports that are longer then the Mat-9K and most other purpose built 9MM AR uppers. The mag adapter Matador Arms sells is about 9.5mm more forward over the magazine. About the same location as many 9MM dedicated Glock lowers. The Colt mag adapter also needed a little longer ejector. See the picture below. The image that works is a modified Silvan arms mag adapter I made a new ejector for.



The Colt mag adapter ejector I made that worked in the picture below is the silver one behind. The OEM one is the blued one in the front.




The other thing I don’t like is the bolt hold open isn’t in the upper. It only works if you have it in the lower. Again this isn’t a big deal for me, I have added it to other uppers and can also make the Stern defense adapter work, but I think it should be in the upper like it is in New Frontier Armory, Spartan Arms and Aero Precision uppers. Charge $50 more if you have to and if they don’t need it it’s easy to remove. It’s cheap, simple and reliable.

For some here looking to put this on a registered full auto lower, sorry, no way for the bolt to trip.

So who is this upper for?​

Me! lol. Anyone who wants to try a bufferless 9MM AR but doesn’t want to spend a lot of money.

Would I recommend it?​

Yep! It’s a good value. You can get a Spartan Arms 9MM lower for 100 bucks and if you want LRBHO, Spike Tactical sells for around $150. Just be aware if you are going to use your SBR AR lower and a mag block, you would need a new, longer ejector. unless you bought a mag adapter from Matador Arms. Matador Arms now sells lowers too, but I don’t know much about them.

Bonus opinion, YAY!

Why I think Brownells discontinued the BRN-9?​

Could be a couple reasons. At first I thought it had something to do with the pistol brace fiasco. They originally did all the videos of the upper with a brace and later re-did the videos with an SBR and stated this was do to negative feedback from the AFT and the comment section blowing up. I’m sure the pistol brace fiasco destroyed the sales of this upper.

Now that I know about the ejection problems with mag adapters, I think many people trying mag adapters with thus upper are having problems. I wouldn’t be surprised if that had something to do with it. Many might try it as I did with a mag adapter they already had and if it was a Stern Defense or Sylvan Arms adapter they wouldn’t understand. They would spend a lot of ammo thinking it would break in and get better. It only chokes 10%, and eventually would conclude something must be wrong with the upper, it doesn’t work and return it. Brownells has a 100% satisfaction guarantee!

I have about 600 rounds through it. I will follow up when I get some more trigger time. Feel free to post any questions. I will be happy to answer them if I can.
Link to uppers: https://matadorarms.com/product-category/9mm-upper-receivers/
Link to Matador Arms Facebook page: https://www.facebook.com/matadorarms/
Link to HB Industries: https://hbindustries.net/store/shop/mat-9-brownells-brn-9-locking-charging-block/
Link to the A-3 tactical grip: https://a3tactical.com/10-modular-vertical-foregrips-b-t-only/
Link to my next Matador Arms build using the Mat 9: https://a3tactical.com/triad-bullpup-chassis-for-mat-9-upper-receiver/​

 

[CoffeeFreak]

 

[CoffeeFreak]

 

[MPXGuy]

I have a Mat-9K incoming. Thanks for the write-up. I'm going with Colt mags. Glock mags are good and reliable but I've had the metal mag release eat up the polymer on mags over time on my adapter and the mags will just fall out. Long term the Glock mag could last a long time with replacement Wolf springs available if you have a Glock lower with a polymer mag release. I've had some bases break too. The polymer gets brittle in really cold weather breaking when hitting the frozen ground during a reload. Colt mags are bulletproof and Wolf sells replacement springs.

 

[CoffeeFreak]

I have a Mat-9K incoming. Thanks for the write-up. I'm going with Colt mags. Glock mags are good and reliable but I've had the metal mag release eat up the polymer on mags over time on my adapter and the mags will just fall out. Long term the Glock mag could last a long time with replacement Wolf springs available if you have a Glock lower with a polymer mag release. I've had some bases break too. The polymer gets brittle in really cold weather breaking when hitting the frozen ground during a reload. Colt mags are bulletproof and Wolf sells replacement springs.

You are correct on everything. I have a lot of Glocks and a lot of Glock mags. In a perfect world you can usually replace mags, they are supposed to be consumables, to a point. Virginia democrats just passed a bunch of gun bans that's sitting on the governor's desk. Lets hope it's vetoed. I wouldn't vote for him for dog catcher if he didn't. If he doesn't the mags you have are the mags you will ever have, unless the supreme court decides to do what is constitutional and say NO NO. So steel mags that can last are a good idea. I have a bunch of Metal Form mags and started running them last week.

They run flawless and the LRBHO works. Have to admit they look better too. I did have to make a new ejector to eject a little sooner. It kept ejecting too late and was choking on spent brass.




New ejector length that worked (silver one to the rear) compared to the OEM ejector (blued steel one in the front)

 

[CoffeeFreak]

The firing pin is going wonky after only 800 rounds. The tip is mushrooming and bending. I know Matador arms will send me a new one but I am thinking about passing on their titanium one and going with the Wilson Combat Bulletproof tool steel firing pin. I haven't had this problem with other AR-9s I have. Thoughts?

 

[sniperdoc]

First thing that comes to mind is that the firing pin is too long, have you measured it?

 

[MPXGuy]

First thing that comes to mind is that the firing pin is too long, have you measured it?

I second that.

 

[CoffeeFreak]

First thing that comes to mind is that the firing pin is too long, have you measured it?

I will look into that. Thanks!

 

[CoffeeFreak]

First thing that comes to mind is that the firing pin is too long, have you measured it?

Well, you may be on to something. Thanks a lot Shane! Longer then the FP in my other bolts, and that's with the head mushroomed.

Dave from Matador Arms saw my post about this on Reddit and let me know he mailed me a new pin today.

I also ordered a couple of spares fro PSA.

 

[MPXGuy]

Coffee I got my upper and I can't get it to feed more then a couple rounds. The rounds aren't chambering. FTF. Think there is something wrong with the upper?

 

[CoffeeFreak]

Are you using a mag adapter? What manufacture mags are you using? In my experience with Colt SMG mags it's the the mag. The Colt mags run great with a Colt cut bolt because it strips deeper from the mag, but with hybrid bolts like the Mat-9K the mags have to be tuned to run. The rear of the round sits too deep in the mag and the feed lips have to be tweaked to make the round sit level. Bring the rear of the round in the mag up or the bolt won't strip the round.

Put one round in the mag to check the right feed angle and two rounds in to check the left feed angle. It's more often a problem on the right then the left. If the round isn't supported by the rear of the follower and not level when you apply a little finger pressure on it the bolt will miss the rear of the round when it cycles.

Example



You have to bend the front of the feed lips out slightly. I use a pair of channel locks. If you bend it too far the rounds will pop out of the mag. If I bend it to far, I find setting the mag on it's base and tapping the feed lips where I bent it with a hammer will close it up.



When you get it right the mags rear will be supported and the the rounds will feed fine.

 

[MPXGuy]

Are you using a mag adapter? What manufacture mags are you using? In my experience with Colt SMG mags it's the the mag. The Colt mags run great with a Colt cut bolt because it strips deeper from the mag, but with hybrid bolts like the Mat-9K the mags have to be tuned to run. The rear of the round sits too deep in the mag and the feed lips have to be tweaked to make the round sit level. Bring the rear of the round in the mag up or the bolt won't strip the round.

Put one round in the mag to check the right feed angle and two rounds in to check the left feed angle. It's more often a problem on the right then the left. If the round isn't supported by the rear of the follower and not level when you apply a little finger pressure on it the bolt will miss the rear of the round when it cycles.

Example

View attachment 39565

You have to bend the front of the feed lips out slightly. I use a pair of channel locks. If you bend it too far the rounds will pop out of the mag. If I bend it to far, I find setting the mag on it's base and tapping the feed lips where I bent it with a hammer will close it up.

View attachment 39566

When you get it right the mags rear will be supported and the the rounds will feed fine.


View attachment 39567

Thanks! Your tuning method seems to have done the trick. The rounds hand feed and eject without problems. I plan on taking it out to the farm this weekend weather permitting. I'll report back. Metalform mags are hard as fu** to adjust the feed lips! Dura Mags are pretty easy.

 

[MPXGuy]

I fired 200 rounds of four different brands Every round fed except the bolt keeps locking open on the next to the last round. I don't think it's the upper. It's not the mags because it does it on both the Metalform and Dura mags. I am trying to figure it out.

 

[sniperdoc]

Well, you may be on to something. Thanks a lot Shane! Longer then the FP in my other bolts, and that's with the head mushroomed.

Dave from Matador Arms saw my post about this on Reddit and let me know he mailed me a new pin today.

I also ordered a couple of spares fro PSA.

Mike, did you get to try another FP?

 

[CoffeeFreak]

Mike, did you get to try another FP?

Yes, ran it today. All is well with the Mat-9K.

 

[sniperdoc]

That's great! It's definitely frustrating when you pay a lot of money for something, then it doesn't work, but at least this one was an easy fix.

 

[CoffeeFreak]

I fired 200 rounds of four different brands Every round fed except the bolt keeps locking open on the next to the last round. I don't think it's the upper. It's not the mags because it does it on both the Metalform and Dura mags. I am trying to figure it out.

You probably figured it out, but in my experience when every mag locks open at the next to the last round on a Colt mag adapter either the mag adapter is a little too high or you need to take a little off the LRBHO tab, here in the picture. Sometimes you can take a little bit off the bolt release if it's dedicated to the Colt mag setup but I go between uppers and setups.

 

[CoffeeFreak]

That's great! It's definitely frustrating when you pay a lot of money for something, then it doesn't work, but at least this one was an easy fix.

I don't have a lot of experience with titanium AR firing pins. Never had one before. Matador Arms sent me a new one, same as the one that came with the upper although the length of other pins I measured in other guns. In studying the properties of titanium compared to the tool steel firing pins, I am not quite sold on the titanium firing pins. I put a tool steel firing pin in I bought from PSA. Lets see how it holds up.

 

[MPXGuy]

You probably figured it out, but in my experience when every mag locks open at the next to the last round on a Colt mag adapter either the mag adapter is a little too high or you need to take a little off the LRBHO tab, here in the picture. Sometimes you can take a little bit off the bolt release if it's dedicated to the Colt mag setup but I go between uppers and setups.

View attachment 39590

I figured it out. It works reliably now. Next on my to do list is CeraKote my upper and lower a burnt bronze and pick an optic. Thanks for your help.