As blow back is not required in revolver cartridge, sound, spark and realism become major concerns.  These are some designs of revolver cartridge by different manufacturers.

KSC King Cobra 6 inch model revolver, note the metal insert inside barrel and firing mechanism
 

KSC Revolver Cartridge

This new design is used exclusively by KSC revolvers.  Similar systems can be found in Marushin and Rocken.  Compared with Marushin's and Rocken's design, cap is placed more near to the head of cartridge in KSC system.  Therefore less sparks and sound will be lose when fired. Only 7mm Cap cartridge is designed.
Number of parts: 4
Pros: Very loud, good spark, 1:1 scale can be done as ignition take place inside cartridge.
Cons: Difficult to clean the head..
 

MGC Revolver Cartridge
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This design is used by MGC, Kokusai and Hudson revolvers.  System is developed long time ago and detonator is built in the cylinder rather than inside cartridge.  Cartridge is passive in this system as it only serves as link between hammer and detonator. Only 7mm Cap cartridge is designed.
MGC Revolver Cartridge system is embedded in other types of model gun like Shotgun and Ultra compact arms.  Like the MGC Remington M31RS shotgun and Hudson Twin Barrel Shotgun, they are using similar systems.  Hudson Derringer is also using similar system.
Number of parts: 3
Pros: Very loud, good spark, easy to clean (the cartridge, not the gun).
Cons: Not in scale as it has to be shorter to fit into the cylinder with detonator.
 
 
 

Little tips on revolvers cartridge

• MGC has a silver plate revolver cartridge on market.  Although it looks not as real as copper cartridge, it is easier to clean.
• KSC's cartridge is so far the best cartridge in market. If you want something even better, Mulberry Field cartridge must be your choice. Marking are engraving on bottom of cartridge and it looks very cool.  But you need to pay the price for quality.
• Kokusai had good silver plated .38 cartridge came with the box before, but now it is ceased in production. See my S&W M36 page under "revolver" section to see them.
• Revolver should use 7mm "S" Cap to achieve the best spark and sound.  The Cap itself is black in colour instead of red.