This is a performance test for a custom built Tokyo Marui Hi-Capa. The customer has complained of two valve knocker cover plates breaking (Tokyo Marui Part # H51-52). Prior to sending the pistol to the customer, I'd ran approximately 200 rounds through the pistol to confirm functionality.
The first plate broke shortly after he'd received the pistol, within a claimed half a mag of firing. I'd sent him a second plate, which he said he'd snapped in less than 10 shots of firing. Each time it broke, the sear slipped out of place, causing the gun to fire in uncontrollable full auto fire.
This time, I'd requested the customer to send the complete pistol back to me so that I could oversee the installation of the plate and to check and confirm durability and performance. I'd replaced both H51-52 and H51-46 with brand new parts I'd had in inventory. By the end of this test, I would have put through almost 600 rounds through this pistol, with zero problems as described by the client.
To date, I can not figure out how the customer could have possibly broken the part. I have never seen nor heard of such a break, nor can I imagine any mechanical reason for such a break to occur. I can only attribute this problem to user error of some sort, but even in that regard, I can not imagine how he could have broken the part under normal use.