MP5 Disassembled - Upper Troubleshooting

Modified on Sun, 21 Dec at 1:13 AM

The majority of upper-related issues are either due to an OEM issue or the denial blocks. If it is not functioning well from the factory, we can not assist with that and it should be sent for RMA repairs.


  • Issue: The slip trip doesn't slide past the rear denial block smoothly.
    • Solution: Simply Dremel/file the slip trip until it clears the denial block fully. We suggest pushing the slip trip in each direction (side to side and up and down) as you slide it past the denial block to ensure there is zero chance of it catching/rubbing against the denial block.
      • DO NOT MODIFY THE DENIAL BLOCK! EVER!


  • Issue: The lower does not fully mount up on to the upper for a Century AP5-P made after early-2025.
    • Solution: Verify you are using the latest revision of the lower you purchased. All of our lowers following batch 4 were modified for this change to the denial block in the underside of the AP5-P. Some Leber V2s have been updated for this change, verify with the seller.

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