Troubleshooting

Have you read the instructions? We know... But please read the instructions for helpful videos and written steps for installation and trigger modification.

Have you installed the buffer tube? Full-Size and Reverse Stretch MP5’s will most likely need to be short stroked to maintain compatibility with the AR15 FCG. This is due to the hammer having a pivot point that is closer to the firing pin than the MP5’s original FCG, therefore is shorter. The shorter hammer presents the possibility of the bolt carrier traveling past the hammer, and locking the bolt carrier behind the hammer. The silicone buffer provides a soft bolt travel limit. The buffer is not needed in MP5K’s since they have less bolt travel.

Have you installed the shelf insert? Semi-Shelf LS5's come with 2 different shelf inserts to fine tune the fitment of the LS5 to the MP5 or MP5K receiver.

Ejection issues? After significant testing we found that replacing the bolt in Zenith specific MP5's helps to resolve ejection issues. We suggest the RCM MP5-E. 

Smooth cycling issues? Some hammers need a 27-30 degree chamfer on the top front of the hammer. This will allow the bolt carrier to cycle smoothly on top of the hammer.