Loading MGC CP-BLK cartridges (cap as seal)

Here's original MGC instruction for loading CP-BLK cartridges.

Originally BLK (also called open) was the first cartridge type to provide blowback action. CP-BLK (cap piston) is the first modification towards a closed cartridge, and it uses a spent (empty) cap as a seal on its piston. The third, and latest version was CP-HW, with a rubber o-ring instead of cap, simplifying handling of cartridges.

Description, assuming you start with a new, clean cartridge:

1. unscrew the top part of the shell
   
2. use supplied MGC tool to push out from bottom two internal parts: piston and insert. Instead of original tool (often lost) you can use a wooden or plastic stick. Metal stick, such as screwdriver, might scratch the bottom and insides of the shell.
   
3. (not shown) if the cartridge was fired, remove spent cap, clean thoroughly all parts.
   
4. put the insert into the bottom part of the shell, align it so it goes into the hole.
   
5. push cap inside, facing upwards (charge toward the opening), using supplied plastic tube. This tube has 7mm external diameter, so it can push cap on edges, not touching the charge. I suggest not using anything else to avoid damaging inside of the shell, or accidentaly setting of the charge.
   
6. take an empty (already shot) cap and punch a hole in it using supplied metal rod. To jump-start you after buying a brand new model, a sheet with special "caps" already with holes was included in the box.
   
7. put cap with hole on the piston, cap bottom against flat part of piston.
   
8. push piston into the bottom part of the shell, so that its top (flat) part is flush with the shell.
   
9. screw top part of the shell onto the bottom part, making cartridge ready for firing
   

Ah so this is what they are for

Yup, that's it :-)

The ones you have shown are Hudson's variant of CP, but usage is the same. Difference is that their version is not made from a normal cap. Maybe it was due to MGC patents? Or MGC worked directly with Kanecap company, while Hudson for some reason could not do that and had their own "plastic seal" production line? I have no idea... Maybe someone knows more.

MGC starter "cap seal" sheet looks just like normal cap sheet, except it looks as if aliens have eaten out the middle: