Cartridge Help (.223 CP)

Hi all.

Well, thanks to a member on these boards I was able to get my MGC M4A1 Carbine up and running again after replacing the missing little part. I ordered a load of cartridges as well for it (took over a month to turn up but I got them in the end) and now, looking at them, am a little lost...

Some of the cartridges came with pistons(?) that had rubber O-rings on them but there were others that did not although I suspect they work in exactly the same fashion? I have included a picture below in case someone can shed some light on this (and on whether they should be loaded into the cartridge in the same way as the rubber O-ring type).




Also I found, when firing the old cartridges I have, that sometimes they don't always fire and was wondering if this is because I am not loading it correctly or not pushing the cap down the right depth, I didn't get a loading tool for it so have been improvising and just pushing the cap down as far as it'll go - is this correct?

Inner without an o-ring requires either a used cap (with a hole) or a special plastic part to act as a plastic "o-ring".
You can see such part here, but it's easier to just use spent caps:
https://mp40modelguns.forumotion.net/t2478-hudson-sten-mkii-madsen-m1950

Hi Ammo,

This drawing copied from one of smootik's posts should also help hopefully:




The pistons without the rubber 0-rings are shown as CP-BLK.

The spent cap will need some silicone grease on its edges to give good gas-seal and ensures the piston travels along the cartridge without tipping over.

Thank you very much guys - AWESOME help. I still have the rubber type inners from the old carts that came with that M4 so I may try changing the inners over for the rubber ones and see how that works.

Also Cerwyn, are you familiar with the disposable carts and the PFG models they can be used with? Have been looking at one am very much interested in getting (have emailed them asking about prices on the disposable carts and if they have any of them in stock) but thought I'd see if you may have one that you've used/tried and what you thought of it.