Mossberg 590A1: Shell Hanging in Magazine Tube / Cartridge Stop Not Releasing (New OEM Stop & Interrupter Installed)

[Spectre09]

Hey everyone,

I'm looking for some diagnostic insight on an issue with my Mossberg 590A1, 12 GA.

The Issue:

When cycling the action fully to the rear, the shell in the magazine tube will occasionally fail to release onto the elevator. Instead, it stays locked in the magazine tube behind the cartridge stop.

If I reach into the loading port and press the cartridge stop flat against the receiver wall with my finger, the shell immediately pops out under full magazine spring tension.

What I've Already Done / Replaced:

• Replaced both the cartridge stop and cartridge interrupter with brand-new factory OEM parts.
• Verified that both locating pegs are properly seated in their respective receiver detents/holes.
• Verified that the magazine tube spring and follower move freely and have plenty of tension.
• On initial reassembly, the shell would not release at all.
• I completely removed the trigger group, reseated everything, and made sure the trigger housing was pushed firmly and flat against the right receiver wall before tightening the trigger pin/bolt.
• That adjustment improved the feeding reliability significantly, from essentially 0% to approximately 90%, but the shell still hangs up roughly 1 out of every 10 cycles.

Where I'm Stuck:

Since the cartridge stop and interrupter are brand-new OEM parts, I'm trying to determine what is preventing the cartridge stop from being fully cammed out of the way.

A few things I'm wondering about:

• Action Slide Bars: Is it possible for the camming surface/bevel on the right action bar to wear or become damaged enough that it doesn't depress the cartridge stop completely against the receiver wall?
• Trigger Housing / Receiver Fit: Could slight movement or clamping tension from the trigger housing allow it to shift just enough to interfere with the cartridge stop?
• Elevator / Linkage: Could an issue with elevator timing or linkage be interfering with the action stroke and preventing the stop from being released consistently?
• Receiver / Internal Fit: Is there a specific area of the receiver or cartridge-stop channel that I should inspect for wear, deformation, or interference?

Has anyone experienced this type of intermittent hang-up on a 590A1 where replacing the cartridge stop and interrupter with new OEM parts did not completely resolve the issue?

I'm mainly looking for guidance on what I should inspect or measure next, particularly around the action bars, cartridge stop, trigger housing fit, and receiver.

I've attached a photo showing the area where the shell is catching.

Thanks in advance for any insight.

 

[R32]

I had the same issue with my 590A1. Research of this issue (many cases on youtube and other forums) led me to remove and slightly bend the cartridge stop bar to engage less than it did from the factory.

I presume you have a spare, since you installed a new one - so give that a try.

Frustrating experience considering, but havent had an issue of a shell not feeding since.

 

[CJDO]

I had the same issue with my 590A1. Research of this issue (many cases on youtube and other forums) led me to remove and slightly bend the cartridge stop bar to engage less than it did from the factory.

I presume you have a spare, since you installed a new one - so give that a try.

Frustrating experience considering, but havent had an issue of a shell not feeding since.

I did the same thing. I filed and polished the cartridge stop because mine came with a pretty nasty burr from the factory. Bent it back as it was over engaging like you said. No issues after that.

I’ve seen some people mentioning similar QC issues with that part as of the last couple years.