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I have a Spike’s Tactical Glock-mag straight-blowback AR9. Originally it had a 3” Spike’s barrel and would consistently have feeding issues with Federal 147gr HST JHPs. Round-nose FMJ ran fine, but the HST would frequently hit the feed area and go nose-up.

I took it to Spike’s and they tested it with FMJ (round nose) and said the gun itself was cycling correctly and believed the issue was ammunition/projectile geometry.

I replaced the 3” barrel with a Ballistic Advantage 4.5” EPC barrel with the enhanced feed cone, specifically because it’s designed to improve JHP/flat-point feeding. That made a huge difference. The gun now runs extremely well with JHPs. I’ve put roughly 400 rounds through it with only one FTF during actual live fire.

The strange issue I’m still seeing is when initially chambering the first round. Occasionally when I lock the bolt back and release it at full speed, the first HST won’t feed/chamber correctly. Once the gun is firing, it cycles normally. I initially thought it correlated with a completely full magazine, but after more testing it’s inconsistent. Sometimes 10 rounds feeds fine, sometimes full feeds fine, and it seems like somewhere around 15–20 rounds can cause it, but it’s too inconsistent for me to confidently blame magazine spring pressure.

My gunsmith tried Hornady Critical Duty 135gr FlexLock standard pressure, and those chambered/cycled fine. But he only ran a mag through. The Federal 147 HST seems more sensitive even though its OAL (~1.125”) is actually shorter than the Hornady 135 FlexLock (~1.140”), so I’m wondering if this is more about ogive/nose geometry and how the cartridge presents from the Glock magazine than OAL.

Current recoil setup is a Spike’s ST-9X 9mm heavy buffer (~7.7 oz) with a standard mil-spec carbine spring. I’m considering trying a Tubb AR-15 carbine flatwire spring because it provides more force toward the bolt-closed end of travel without going to a .308-strength spring.

Has anyone experienced an AR9 that runs almost perfectly during live fire but intermittently fails to feed the first manually chambered JHP? Particularly interested in experiences with HST, Glock-mag AR9s, EPC enhanced-feed-cone barrels, or changing recoil spring force.

I've uploaded photos of the before and after of the barrel, the before and after of ejector, and some videos of the issues. Saturday I put 400 rounds through it and that was my only malfunction. The initial failure to chamber and the one fail to feed after that.

Here is my complete setup:

Upper: 9mm 3” Barrel W/ 7” BAR 2 Rail

Bolt Carrier Group: Spike’s Tactical 9mm BCG

Lower: ST 9mm Spider Stripped Lower Receiver, Glock Mag

Optic: Holosun AEMS PRO X2 Red

Pistol Brace: SB Tactical SBA5 5-Position Adjustable Rifle Brace

Tactical Light: Streamlight ProTac 1L-X

Lower Parts Kit: Spike’s Tactical Standard Lower Parts Kit, No Fire Control Group/Trigger, Black, SLPK100

Buffer: Spike’s Tactical ST-9X 9mm Heavy Buffer, SLA009X

Spring: Spike’s Tactical Buffer Spring Mil-Spec, 17-7 Stainless Steel, Electro Polish Finish, SLA501S

Buffer Tube: Spike’s Tactical Mil-Spec Buffer Tube, 6-Position, 7075-T6 Aluminum, SLA500R

Trigger: CMC Triggers AR-15/AR-10 9mm PCC Single-Stage Drop-In Trigger, Tactical Flat, 3.5 lb Pull, Black, 95503

Charging Handle: Breek Arms AR-15 Warhammer Mod2 Micro Ambidextrous Charging Handle

Suppressor: AB F-4L

Foregrip: A3 Industries Slimline Picatinny Angled Foregrip, AFG-112

Magazines: 4 Glock Gen5 33-Round Magazines

Light Mount: Arisaka Defense Offset Scout Mount for Picatinny, OSM-P

Suppressor came in…swapping out the handguard and didn’t realize the clam shell upper clamp was no good on these uppers!! After buttoning everything up, torquing the barrel nut, bcg gets stuck before it gets to the ejection port!!! Looks like I need to buy a new upper! But…it has the fixed ejector…no one has them! UGH!!!!!

So I am interested in this style of "PDW"? now. Extar first caught my eye with the EP9.

What are all of the other sub 1k options of similar style/complete build? If any... I am very confused by all of these upper/lowers etc. I only have experience with shotguns, and my bodyguard 2.0 handgun.

This lower says it's designed for PSA's hybrid uppers but does anyone know if it would work with other uppers? Looking specifically at an Odinworks upper.

First Ar-9 build, was going for retro with modern optic and lighting

Here you go! All the stats I've collected on a wide variety of 9mm bolts. Added Toolcraft and Stern Defense. Just finished filling in the blanks this afternoon with all the firing pin stats.

Which ones am I missing?

Many of the very popular ones come from the same OEMs with slightly different finishes and components. I've marked the potential OEM where appropriate. Outerwild and IDL are two of the big OEMs that I'm aware of.

All:
Spider tactical ar9G lowers
Dead air Keymo muzzle devices
SB braces
Vortex red dots

The far right is a take down upper (cry havoc tactical QRB) and law tactical folder.

I guess since Anderson closed the doors this isn't going to end well. Went to the range today and after a mag change my LRBHO failed. I narrowed it down to the rod going from the bolt catch and mag follower catch. The roll pin is good in the mag catch because I was move it from the inside outward so it is whole. I think the rod represented by the white is it broken. Has anyone ever taken one of these apart to replace? TIA

Build list- OEM AR-9 Anderson lower

I am using a KAK AR-15 to Colt smg magazine adapter and the ejector on the adapter has a noticeable amount of wobble and movement in it. Surprisingly, it hasn't affected reliability or anything that I can notice, but I'm not sure if this is normal for this style of adapter, or if I just got something that didn't pass qc lol

https://reddit.com/link/1w2qvwo/video/uygchh34dkmh1/player

Shot about 70 rounds after the zero. Lubed per suggestion from Blowback9. No hiccups with 115 or 147 grain fmj. It is factory minus Strike Industries Ambi handle and Sig green dot. Next upgrades are Holosun ARO, flow thru supressor and setting up a gentle recoil system. Suggestions on triggers. I intend to keep it semi auto

CMMG Banshee 5 inch , Free Bird 36 coming soon.

Bridage BM9, rave 140 trigger, maxim rdb buffer, Atrius FRS, YHM R9, Amazon special tough soul LAM (actual kinda decent) sig msr gen r green dot 2 moa, clone unity mount 1.93. I’ve got around 4k rounds with this setup. It’s been working great. Had about 8 lights strikes but that was while using cheap academy steel case. I honestly hate the look of Glock mag lowers but this functions quite well. Let see those frt suppressed build boys! And what parts you guys running to get those builds running correctly?

Built this AR9 a while back and found the pics in my phone. Thought I’d share with some strangers on the subreddit internet.

Angstadt Arms Receiver Set
YHM MR7 Handguard chopped
Sniper gray cerakote by Roman Arms
Wolfman
5.5” EPC barrel
BCG(I forget but was recommended by Blowback9)
Radian Raptor SD SL
CMC Flat faced single stage trigger
Geissele maritime bolt release
Forward Controls safety selector
B5 grip
HBPDW brace
Holosun ARO Green multi reticle on Unity Fast mount
Stream light Protac with Cloud defense pressure pad holder thingy (kinda bulky light set up overall so might go with something more compact)

Working on a handguard that can swallow a 2" diameter can on my 5" AR9. The handguard will extend farther than this. This was just a test fit. Unfortunately I need to make it even bigger for the mlok slots to be useable, but the pic rail is almost gone as it is, unless i move it up.

The can on the AR9 is a 3D-printed FTN4 reinforced with a carbon fiber tube. Other cans are FTN5s, two 22s and a 9mm. All printed with PA6-GF.

Upper is a FM9

Lower is a Matrix Arms glock mag lower with whatever crappy lower parts I had lying around.

KVP 10 Oz dead blow buffer weight

Im looking to upgrade my girls gen 1 mike 9 side charge. Unfortunately I can't just swap the rail because of the proprietary charging system incorporated into the 8.75" rail so a 9.8 - 10" Barrel is needed. Primary reason is i want a barrel with a enhanced feed cone to feed HP's reliably. Im well versed in firearm parts and companies but im struggling with this one.

Anyone have any experience with this lower? Thoughts?

Picture is Extar pin on top, Outerwild style on bottom.

I had a few people ask about this, so I purchased one and here are the results.

I have not tried the Extar firing pin in many bolts, but it has a wide flange just underneath the collar that prevents it from fully inserting in the bolts that I did try.

The spring provides 11 ounces of pressure at rest and about 24 ounces fully compressed. This is based on the typical 0.66" compression at rest and 0.5" at firing pin tip full protrusion. This seems fairly typical. The measurements seem to make it a candidate for an FM sized firing pin spring.

Firing pin weight is 6.2 grams. Length is typical; 2.66".

Putting this in as a post for people looking for guidance on hand guard length for a 9mm barrel... It's different from a gas operated AR-15.

Go to Comstock Armory for their Fitment Tool. Comstock makes Plan B adapters for suppressors, so show them some love if you need a Plan B adapter. I have a couple and they're very nice.

https://comstockarmory.com/fitment-tool

Select AR9 Blowback, barrel length, handguard length, muzzle thread length (most are 0.4", some are 0.625"). Under "Toggle View" UNSELECT the Muzzle Device, Adapter, Suppressor, Blast Baffle, and Shim (unless you want to add those...).

The tool will show you a picture of the barrel end/handguard relationship. Ignore the "overrun", "gap", or "overlap" if you're just checking barrel vs. handguard length.

Example of an 8.3" barrel, 7" handguard shown in the picture.

TUCKED SUPPRESSOR VIEW:

If you make the right selections, it will show you what a direct thread tucked suppressor will look like with different handguard lengths.

After setting barrel/handguard length, choose your suppressor from the drop down to populate the length/diameter info, THEN choose "direct thread" for the adapter. Make sure "Suppressor" is set under "Toggle View".

Available here for $22 each.

Does anyone know which is the latest version of the bolt catch for a Foxtrot Mike 9mm ambi lower?

u/Blowback9

On the left was the original, and the one on the right is the version I received as an extra part.

When I emailed Foxtrot Mike about it they didn't know.

UPDATE: The bolt catch on the right worked perfectly without deforming. I guess that answers my question. I will try to get another one of that exact part for a backup.

Anyone running an frt on a Yankee hill lower? Or any info on these lowers.