Did you clean either firearm before using.
Cartridge stop and cartridge interrupter issues on Fabarm shotguns typically present themselves as feeding failures, such as a failure to feed (FTF) from the magazine tube or a double-feed jam.
While Fabarm shotguns (like the STF 12, SAT8, L4S, or older H&K imports) are generally highly regarded for their build quality, their shell-handling mechanisms operate under very tight tolerances.
When these parts malfunction, the root causes usually stem from mechanical alignment, debris, or a separate component mimicking the issue.
Common Symptoms & Mechanical CausesThe Cartridge Stop (Shell Latch): This component holds the shells inside the magazine tube.
If it does not retract far enough when the action is cycled, the shell remains trapped in the tube (Failure to Feed).
The Cartridge Interrupter: This component's job is to block the second shell from escaping the tube while the first shell is being fed onto the carrier. If it fails to engage, it allows two shells to slip out at once, causing a severe double-feed jam.
Debris and Carbon Buildup: Because Fabarm semi-autos use a highly efficient gas system, carbon fouling, unburnt powder, and factory grease can accumulate behind these small spring-steel latches inside the receiver walls.
This buildup restricts their full range of motion, freezing them in place.
Related "False Flag" Issues on Fabarm Shotguns Sometimes a suspected cartridge stop issue is actually caused by another component:
Melted or Sticking Magazine Followers: On older H&K/Fabarm imports, the factory used a plastic magazine pusher/follower. “It turns out that some of the early guns have a plastic "pusher" to move the shells through the tube... it melted the follower to the tube. It caused the follower to stick.” -- This mimics a cartridge stop failure because the shell fails to exit the tube. Replacing it with an aftermarket aluminum follower completely solves this problem.
Rim Dimensions & Out-of-Spec Ammunition: Fabarm chambers and latch configurations are engineered tightly. Budget ammunition with inconsistent, oversized, or overly thick rims can hang up right at the lip of the cartridge stop, making it feel like the latch is stuck when the shell rim is simply jammed against it.
How to Troubleshoot and Fix Perform a Deep Solvent Clean: Strip the shotgun down and remove the trigger group. Clean out the recesses on the inner walls of the receiver where the cartridge stop and interrupter sit. Ensure there is no gummy residue behind them preventing them from springing back and forth.
Inspect the Follower and Spring: Ensure your magazine follower slides smoothly all the way to the end of the tube without binding. If it hangs up or feels rough, clean the inside of the magazine tube or swap the follower.
Fabarm's shell latches rely on precise tension. If a latch has been slightly bent outward or inward (often due to forceful disassembly or high round counts), it won't interact properly with the bolt slide.
Gunsmiths typically fix this by removing the latch and applying incredibly micro, incremental bends to restore its factory profile.
Test with Different Ammunition: Switch to a premium brand of ammunition to see if the issue persists. If the gun cycles premium hulls perfectly but chokes on cheap target loads, the issue is ammunition rim variance rather than the gun's internal components
