MGC HW CP carts getting damaged

I have a MGC ABS XM177E2 (M16A1 Commando) that is firing quite well on FULL and SEMI. I am currently really enjoying this model but realized that some carts got damaged badly/destroyed. The threads got blowed off and the upper part of the cart gets widened.

Does anyone know what the issue may be? Maybe the piston travels not easy enough, but I do lightly grease the carts inside ...



Will have to look for some replacement carts anyway ...

Hi 'Mike

Wow those cartridges are taking a real beating aren't they

I've only seen similar damage on old cartridges that have been used over and over again. Repeated firing can cause the screw-on top to spread and threads to fail but those in your photo look almost like they've been squashed. There's a definate bulge all around the threaded area.

Is it possible that the detonator chamber or the det. pin is positioned too close to the bolt face What I mean is could the cartridge be squashed between the bolt-face and the bottom of the chamber

How many cartridges have failed like this

Thanks for your reply. I did not yet notice anything unusual with the gun, but may have to take exact measurements.

I have "killed" approx. 10 carts like this, they were fired 10 - 15 times I'd say before they broke.

I wouldn't expect any cartridge to wear out that badly after only 10-15 shots 'Mike.

Are there any signs of damage at either end i.e. cartridge base and neck

The old cartridges I've seen in the past, having been fired many, many times, show a gradual spreading around the threaded base of the cartridge "top" leading to loss of gas pressure and poor firing. Your photo looks almost like the cartridge has been stood on end on a solid surface and hit hard by a heavy hammer

I've seen Marushin 9mm and MGC 220s break at the threads but only because they'd been damaged by a "stove-pipe" jam. They were impossible to unscrew by hand and broke when more force was applied in a vice...

How many caps do you load into these cartridges Is it just 1 x 7mm cap or are you using 1x 7mm and 1 x 5mm

Of course it is only one 7 mm cap . The MGC Cap Piston design is a good design and seals the hot gases well. One cap is powerful enough. I do not see what caused the trouble. The gun is operating fine. Anyway I used these carts with another MGC M16 I do not longer have. Maybe this gun caused the damage. I will have to test some new carts and see if they get damaged too.

MadMike wrote:

Of course it is only one 7 mm cap . The MGC Cap Piston design is a good design and seals the hot gases well. One cap is powerful enough. I do not see what caused the trouble. The gun is operating fine. Anyway I used these carts with another MGC M16 I do not longer have. Maybe this gun caused the damage. I will have to test some new carts and see if they get damaged too.

The use of 2 caps can blow cartridges apart but as you rightly say, the MGC c.p. design only needs a single cap.
If you've used these cartridges before, how old are they 'Mike You don't suppose the brass material has got brittle with age do you
Having said that, the majority of my cartridges are over 3 years old (some 5 yrs) but I've only seen 2 break during firing, a few others due to "stove-pipe" damage.