Good afternoon all,

I'm seeking some help from some of the experienced members and gunsmiths on the board.  First and foremost, I did quite a bit of reading here on the board prior to making my purchases, including the "lots of 9mm information" thread put together by Droppoint.

Here's my build details:

Right to Bear 80% lower
Davidson Defense Upper and Finish Your Build kit
7 5/16" x 1.25" diameter round buffer tube (not mil-spec)
KAK Industries 5.5 oz buffer
Standard AR-15 Carbine spring
United Defense Labs Ind. BCG
10.5" 4150 CMV 1/10T barrel, unknown manufacturer but it has an actual feed ramp not just the typical cone that I've seen on most 9mm barrels like the Faxon
Omega Manufacturing LPK

Combined buffer and BCG weight: 19 oz

Got capped by the system, so adding a second post with more details

I've run approximately 300 rounds through it so far across 5 different brands, all 115 grain:
Tulammo steel
Sellier & Bellot brass
CCI Blazer brass
Winchester White Box brass
FedArm brass

The only ammo that runs reliably through it is the Tulammo and S&B...the rest have issues virtually every or every other round, even stove piping in some cases.

Prior to making my purchase, I contacted DD to ask about the buffer weight since it seems most here are suggesting heavier weights are required.  The rep I spoke to stated they've sold a ton of these kits with no issues.  Fast forward to after my first day of testing, I contact them again and speak with a different tech- this time getting a different story and he's heard from a number of customers with similar issues.

At this point I've spoken with a few techs now (including a local resource) and I'm getting conflicting information, so I'm hoping I can get a consensus here.  The tech from DD suggested polishing the chamber feed ramp, possibly a heavier buffer, the local tech suggested testing heavier grain ammo such as 124 and 147 ball ammo to see what happens.  If it improves, he suggested getting a LIGHTER buffer.

While I'm technically and mechanically inclined as well as a USN vet, I will freely admit that I am an AR newb.  For being such a simple gun to assemble, they sure seem to be tricky to get running reliably- unless you pretty much copy what one of the other guys has already put together.  Personally, I enjoy the satisfaction of building it myself- plus it provides me opportunities like this to learn a lot more about how it functions.

Thanks in advance!

You are a little light on the buffer/bolt.  Consensus is 21.5 - 23.5 ounces combined, but some run even heavier.  What mag system?  Can you post a pic of this feed ramp and chamber mouth?

just to be clear in your description... I understand a stove pipe to be a fired cartridge that has been extracted and only partially ejected, sticking somewhat vertically and still smoking... or do you mean a failure to feed where the loaded round has not released off the front of the magazine lips and has been trapped by the bolt and did not chamber... regards

Yeah I can post a pic once I figure out how to do it here.  Mag system is Endo mag inserts, standard Magpul MOEs



Yes, similar to what you described- in my case diagonally out the ejection port...as well as a few FTEs- held in place by the extractor on the bolt.

To be fair to the build, I haven't gotten anything to shoot that FedArm crap I bought.  Picked up 2000 rounds from them a couple years ago and it's just junk.  It's been shot through at least 8 different guns and we have FTF issues with all of them- I suspect the powder loads are light.  I've also noticed a more pronounced edge on the round casing, so I think that's contributing as well.

https://imgur.com/IJ3coDg - Barrel feed ramp image

The gun doesn't eject reliably?  There are two types of Endomag inserts.  One doesn't have an ejector that is used with RDB guns, that won't eject properly with blowback guns.

I'm not experiencing significant ejection issues, but it's happened...hard to remember since I was having so many FTF issues.  I'm pretty sure the FTEs were with that crap FedArm ammo.  I don't remember any FTEs with the Tulammo or S&B ammo.

I'm far more concerned about the FTFs at this point.

Can you post a pic of the malfunction?  Do I understand correctly that they turn sideways when stripped from the mag?

No, they're not turning sideways when loading the next round from the mag.  That was my description of the stovepipes (FTEs) that I've had (which haven't happened much at all...maybe 3 or 4 out of 300+ rounds.

During FTFs, the round is nearly always facing straight towards the breach, angled diagonally up with the nose of the bullet lying on the feed ramp.

Looking more closely at that zoomed in pic of the feed ramp, I can see how polishing would help...lots of tiny imperfections on the ramp and feed cone.

I was going to suggest that the cartridge might not be releasing early enough off the magazine due to too long a magazine lip, but I have no experience with the Endo magazine conversion

So the round is pointed toward the chamber, lined up on the feed ramp, but it just stops?  It's not hitting the top of the feed cone?

Gas port?? . These are blowback not impingement, aren't they?

Davidson defense/ delta team tactical is junk. If you want to salvage it pull the barrel and send it to Rudy at macoon armory for a reprofiled feed cone. Both my ar9 builds had feed issues with flat nose and jhp sub ammo. $65 later and all is gtg

I'm glad you found my post helpful!

FTF is frequently caused by the feed area of the barrel.  As stated above, contact Rudy at Macon Armory.  He can either re-profile your current barrel feed area or you can purchase one of his "guaranteed to feed" barrels.  They really are worth every penny.  I had him fix my first barrel and all the problems disappeared, so I bought my 2nd barrel directly from him.  No issues with that one either.

If you want to try polishing the feed area yourself first with a mirror-like polish, that's your call. It may fix it, it may not.

5.5 oz. buffer is generally considered the minimum safe weight for most builds.  Optimally 21.5 - 23.5 oz. bolt+buffer weight, as S4S4U stated above. If your combined weight is only 19oz, your bolt is only about 13.5 oz.  That's seems awfully light for a 9mm bolt.  I run my builds with totals of 21.8 and 23.8 oz.

Some of it may be.........but not all of it........I bought an upper from them and a barrel.........both have served me well. The barrel was sold as being made by a company called gorilla machining..........It has been flawless........gobbles up any 9mm I have yet to run through it...............davidson defense upper with a NFA barrel..........no issues what so ever......................I had Macon rework a Faxon barrel a couple years ago....flawless too

Thanks to all for the assistance- I think I'll try a 7.5oz buffer and reach out to Macon as well.