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Joined:
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Posted: 4/22/2026 12:47:49 PM EDT
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I’m trying to diagnose what appears to be a mechanical compatibility / geometry problem in a PCC build, not a simple ammo or cleaning issue. Setup: Matador MAT-9 upper Foxtrot Mike Ranch Rifle lower Mean Arms ExoMag with ejector Problem: I’m getting a failure-to-fire / abnormal function issue, and I suspect the cause is somewhere in the interface between the bolt, hammer, lower geometry, and magazine positioning. Since I’m using an ExoMag with built-in ejector, I do not think this is just an ejector-absence problem. My working theory is that the issue is more likely one of the following: bolt-to-hammer interference / excessive drag hammer or trigger geometry incompatibility mag height / mag catch depth / round presentation issue overall tolerance stacking between the MAT-9 upper and FM Ranch Rifle lower This does not feel like bad ammo or a routine break-in issue. It feels like something in the system is mechanically not agreeing. What I’m trying to determine: what the single most likely interference point is whether the first thing to investigate is hammer profile, bolt drag, or mag positioning what the cleanest fix is before I start swapping parts or removing material Questions for people who know these systems: With this setup, is hammer profile / bolt drag the first place you would look? Has anyone run a MAT-9 upper on an FM Ranch Rifle lower successfully? Are there known hammer / trigger combinations that play well with this sort of setup? How much suspicion would you place on ExoMag height / mag catch depth versus FCG geometry? I’d especially appreciate responses from anyone who has dealt with bufferless AR9/PCC uppers on unusual lowers or solved a similar drag / FTF issue. I can add close-up photos of wear/contact points if helpful. |
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Originally Posted By riddickbeebe: I'm trying to diagnose what appears to be a mechanical compatibility / geometry problem in a PCC build, not a simple ammo or cleaning issue. Setup: Matador MAT-9 upper Foxtrot Mike Ranch Rifle lower Mean Arms ExoMag with ejector Problem: I'm getting a failure-to-fire / abnormal function issue, and I suspect the cause is somewhere in the interface between the bolt, hammer, lower geometry, and magazine positioning. Since I'm using an ExoMag with built-in ejector, I do not think this is just an ejector-absence problem. My working theory is that the issue is more likely one of the following: bolt-to-hammer interference / excessive drag hammer or trigger geometry incompatibility mag height / mag catch depth / round presentation issue overall tolerance stacking between the MAT-9 upper and FM Ranch Rifle lower This does not feel like bad ammo or a routine break-in issue. It feels like something in the system is mechanically not agreeing. What I'm trying to determine: what the single most likely interference point is whether the first thing to investigate is hammer profile, bolt drag, or mag positioning what the cleanest fix is before I start swapping parts or removing material Questions for people who know these systems: With this setup, is hammer profile / bolt drag the first place you would look? Has anyone run a MAT-9 upper on an FM Ranch Rifle lower successfully? Are there known hammer / trigger combinations that play well with this sort of setup? How much suspicion would you place on ExoMag height / mag catch depth versus FCG geometry? I'd especially appreciate responses from anyone who has dealt with bufferless AR9/PCC uppers on unusual lowers or solved a similar drag / FTF issue. I can add close-up photos of wear/contact points if helpful. |
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Joined:
Apr 2026
Posts:
2
EE: 0% (0)
GA, USA
Joined:
Apr 2026
Posts:
4
EE: 0% (0)
GA, USA
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You've got a significant "hodge podge" of parts that are all pretty proprietary to some extent so finding someone with the same issue or knowledge is going to be tough especially with the exomag involved. I've used a standard lower with exo and endomags without issue with a MAT-9 upper; i'm not saything its your lower thats the problem but the first thing I would do is swap triggers and/or hammers to see. Are you getting a click when you pull the trigger? Any dimple in the primer? Give us more details on the failure you are having. |
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