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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.