r/AR9

Brigade mfg lower, nbs slick side upper, BA 5.5” barrel, yhm r9, Presma charging handle and tube handguard.

147g ammo. She’s quiet!

Love this pairing, especially with interchangeable mags.

Brigade BM-9

- Midwest Industries SD handguard

- Streamlight ProTac HLX

- Holosun ARO green

- B5 type 23 pistol grip

- Arisaka handstop

- Troy Industries BUIS

Ruger RXM

- Holosun EPS MRS green

- Cloud Defensive EPL

I just built this AR-9 and I am looking for a little help. On this build there is no bolt hold open for last round. when the last round is fired from the magazine the follower in the magazine is struck by the bolt with such force that it is becoming dislodged and damaged. The only cost effective solution is to load a snap cap in my mags. Is there any other solution other then buying a different upper that will activate the bolt lock?

build

Foxtrot Mike VFM -9 complete upper

aero precision EPC-9 lower

CMMG LPK

KAK shockwave tube and pistol brace

kak 10oz buffer

31 coil round carbine spring

CMMG. zeroed 36 can

Nemo Arms 8# 300BO spring vs Franklin Armory 17.5# BFS recoil spring.

Only the spring was changed between trials.

Conclusion: Stronger springs increase ROF by about 10RPM per pound increase in strength, and vice versa.

Spring strength measured at bolt fully rearward. Milspec is 12#.

(For those who are unfamiliar, "#" is the traditional abbreviation for "pounds".)

Just got all the parts in today, unfortunately too late to go and shoot it. Build list:

- warscorp builder set

- ballistic advantage 5.5 barrel

- mimtac AR9 trigger

- SB HBPDW 9mm brace

- breek arms 6.7” handguard

- strike industries linear compensator

- vortex sparc solar red dot

- cheap amazon flip up sights

Very excited to take it to the range, but I would be lying if I said I wasn’t afraid of potential issues arising from the mix of parts. Pleasantly surprised by the quality of the BUIS, full metal construction and feel really sturdy. The strike industries linear compensator is also very well made and is super helpful to be able to dial in the length when I’m not sure how everything will fit together.

I should add that the hand guard is just a tiny bit wider on the sides than a "normal" MLOK handguard, so it pushes up on the charging handle in the folded position just a tiny bit. I'm on the fence about returning it for a different rail.

I got out to the rapid fire range this week to test an ARC in a "stock configuration" FM 9mm AR blowback (5" VFM dual charge, ambi lower, A5 tube RMB). I was getting short bursts with dead trigger/light strikes. This setup had already worked just fine with a GMR S7 SS.

I didn't have all my troubleshooting tools/parts with me, but I did catch it on high speed - 3 shots in the FRT string - first shot normal, 2nd FRT normal reset/release, 3rd dead trigger. I did notice that the timing appeared slightly different between the 2nd and 3rd trigger pull/hammer release and the moment the bolt closes. The cam releases control of the trigger before the bolt is closed, which is expected, but if it's too early the hammer may hit the rear/bottom of the bolt under the FP rather than the FP itself.

Traditionally this type of failure in a 9mm blowback AR has been the result of bolt bounce, firing pin bounce, or a cam timing issue. My suspicion is that it's a cam timing issue, but next time I get out I'll do more testing.

The RMB has shown itself to be very effective at eliminating bolt bounce on high speed video.

My troubleshooting is going to be, in this order....

Tried already:

1. change from newer FM firing pin spring (strong) to UXCELL firing pin spring - no change.

Next, in order until something works:

2. Install a BoreBuddy-type timing advance shim (actually bought a 25 pack on McMaster-Carr - Part # 99040A408). Installation video on BoreBuddy web site.

3. Titanium firing pin to help prevent firing pin bounce

4. Stronger Ace Hardware spring for firing pin to help prevent firing pin bounce

That should cover advancing the timing and preventing any FP bounce. From there I should be able to figure out which one is the problem.

Based on this post (https://www.reddit.com/r/AR9/comments/1si3mij/update\_on\_my\_psa\_gen\_4\_with\_arc\_fire/), it may very well just be timing.

Hey guys, so I was able to mill out my own super safeties and Glock frt. I already know there’s many companies selling these, but I’d figured I’d give it a chance. I’d like to bring these to many at the cost of $40 or LESS!! For super safeties and $20 or LESS for Glock FRT, not including shipping (I’m just like you bro, not a big corporation lol). I was blessed with the opportunity to buy a 5 axis mill for pennies on the dollar. I get these coated in nitride or oxide if available ( except Glock frt due to tolerance issues I’ve faced). I just wanted to see if it’s worth manufacturing. All and any opinions are welcome, thank you and have a blessed day! Local pick up in Utah if you’re here lol.

Super safety Includes:

- 4140 Hardened steel Cam

- 4140 Hardened steel lever

- Trigger cutting jig & template

Glock Frt

- 7075 aluminum trigger shoe w/ hole but W/O spring

- x2 : 316 steel round reset (if customizing is needed)

I’ve seen multiple version of these from multiple manufacturers, my specs are within +/- 1% I can guarantee it!!!!!!

Can’t ship to states with certain laws, sorry :(

Just finished this build (so far). Let me know what suggestions or feedback you have in the comments.

Build List:

Silencerco Omega 9k (3 lug)

SMS Laser Axis

BCM angled grip

KAK Enhanced bolt carrier

Holosun AEMS core x2

Scalarworks 1.93” riser

Kynshot RB5015HD buffer

Tubbs flatwire carbine spring

DieFreeCo Kung Fu grip

We The People 2 point sling

Might change some things after I take it to the range a few times.

For context I made a post a week or two ago asking for suggestions for things to try to trouble shoot my issues Ive had getting this ARC frt to work in this gun.

The set up I had for this gun originally was just a kaw valley 10oz buffer weight as well as I trimmed the bolt weight to size.

The issues i was having was I was only getting semi auto fire, OR, if the lever tripped it would get 1-2 bullets and then dead trigger due to light primer strike not setting off the next round. I had noticed that when taken apart and im manually pushing the bolt back to trip the lever (my last post on this sub has a video of this) The lever would not trip anywhere within the whole range of motion of the bolt, at first I thought maybe the buffer weight was preventing the bolt from going back far enough to trip the lever, so i sanded the buffer weight and tested it after each little bit of sanding until the length went from 4.125in to I think its around 3.83in (probably a wee bit too much sanding lol) but at each length there was still no luck getting the lever to trip within the range of the bolt. I was stumped and looking for new information or things to try. I had seen multiple mention firing pin springs and so I tried that. (I tested 3 different springs in total, the stock PSA spring, a Wilson Tactical AR-9 Spring, and the Amazon spring BB9 mentions in his cheat sheet) all of which didnt solve my issue,

BB9 then commented on my last post and provided a link to BoreBuddys arc fire shim for .22.

https://borebuddy.com/product/arc-fire-timing-advance-shim/ is this link

I just got this shim in today and install it and before even shooting it I manually pushed the bolt back and viola! it tripped it, I then was able to assemble the gun and pull the charging handle while holding the trigger in SS mode and it was passing that function check.

I was pumped to go test shoot it as it was the first progress I have seemed to make so far, first test got a 5 bullet burst (biggest I had gotten since i started this build) then followed it with a 2 round burst before getting dead trigger. Cool. its now tripping the lever consistently and the problem now seemed to be something else. After a little messing around I noticed that every time I got good bursts it was after I had already shot a little bit from that magazine. This was notable for me because the last 4-5 bullets to load into the stock 27 rnd mag that came with my gun were very very hard to load and with a full mag my gun even had issues feeding the first bullet.
So I loaded up a new mag fully and began testing this.

First bullet - dead trigger

Charged the handle to eject round with light primer strike - second bullet

I then shot a 2 round burst before dead trigger and then ejected the one with light primer strike - bullets 3 4 and 5

Then I went to shoot again and boom went through the rest of the magazine in burst with relatively no issues.

I loaded my magzine up to 22/27 bullets and right off the bat it start shooting reliably without having to eject any rounds with light primer strike.

I have not tested shooting all 22 rounds it succession yet but between the shim and loading my magazine less I have fixed my issues and my gun in now gunning!

I was just going to reply to the comments in my last post but figured a whole new post would be better for others in my same boat trying to trouble shoot.

So hopefully this can help someone else out and thanks to BB9 for putting me in the know on this shim to help trip the lever a little sooner

Still fine tuning this SS system for the 7” retro N-23/Kitty Kat 9mm build.

I’ve added 3x tungsten weights and 1x steel weight into the KAK enhanced 9mm buffer for a rough total of 10.65 oz buffer weight.

I’m using the standard carbine buffer spring with a plug and two quarters behind it.

Mercury / Davidson Defense 9mm bolt.

PSA Colt Style Dedicated 9mm Lower

RRA 7” Chrome Moly Phos Barrel with FSB

H&R Dedicated 9mm Upper

Fudd SS Cut Trigger, Cam, & lever.

With the stock buffer, I’d get rattles off of 3, 5 or 7 at a time but always returns to normal semi function even in middle SS position. Sometimes trigger will go dead and need to be charged to expend the live round and load the next.

After I added the extra tungsten weights, I figured things would go smoother—but they were just the same as before.. even seemingly worse. I added and removed quarters on the fly at the range trying to troubleshoot, but that didn’t do much.

At first I was thinking buffer weight, but now I’m thinking something else. Any ideas?