Thanks Jerrod It's getting there slowly ! I'm obviously hoping for every cartridge to show Muzzle Flash, not just a few as I'm seeing with STEN so far.I've used 2 methods so far, the first being with my MP38. Both methods need a Detonator Pin with as little restriction as possible for hot gasses to vent from cartridge and through the barrel.My MP38 uses a Det.Pin almost identical to the type used when converting MGC MP40, Stirling and STEN to fire P220 cartridges. These usually have 2 holes drilled through the Brass Ring to allow smoke to vent through. First modification in to Drill as many decent sized holes through the ring to make venting easier.
This is an example seen on a Japanese site recently.
I did try one with a 2mm dia hole bored through the pin itself but found the tip of the pin prone to deforming so I'm staying with just the vented brass rings now.
Next comes Cartridge loading ***I will post some photos of loading method later*** My MP38 uses KSC 9mm Luger C.P. carts with 1 x 7mm MG cap. The only addition was a very small amount of Magnesium powder dropped onto the cap.
My MGC STEN also uses KSC cartridges but for this I loaded slightly differently. The first 7mm cap is inserted normally, with the addition of a very small amount of Magnesium powder.
Insert the Piston. Make sure the top of the piston is dry, i.e. no oil or grease.
Push the Piston into the cartridge about 3mm or so.
Carefully take the Red (MG caps) powder charge out the plastic body by gently prising it out with the tip of a knife. With care, the Red charge will pop out in one piece
Place the Red powder charge onto the top of the Piston.
Add a small amount of Magnesium powder on top of the charge.
To seal in the Magnesium powder, I have found that Magician's Flash Paper works very well.
Using an 8mm dia hole punch, cut out a circle of Flash Paper and gently push it into the cartridge.
Replace the cartridge top.
Try keeping the cartridges upright as much as possible as the paper isn't guaranteed to hold the Magnesium powder inside the cartridge.
Load the Magazine and Fire away 
Muzzle Flash can be very effective. I think the ones that fired without flashing had broken or crumbled Red charges in them (on top of the piston) or possibly the Flash Paper had crumpled up stopping the Detonator Pin striking the Red charge. Practice should sort it.
Only use each cartridge once. Magnesium powder is extremely dirty and even though it burns, it still manages to leave black "soot" and a gritty deposit inside the cartridge and over the Piston an 0 Ring. This dirt will affect cartridge performance and firing if loaded again without thorough cleaning.
N.B. PLEASE note that Flash Paper is extremely flammable and burns very quickly leaving no ash. Similarly, Magnesium powder burns very quickly. Do NOT compress these components into tightly sealed such as the cartridge case as there is a risk of explosion if the Piston was to stick in the cartridge bore.
The advice I was given, and to which I'm complying with is to only use this method with Open Bolt, Metal models. Once I've mastered this method, there may be possibilities of trying it in closed bolt models but only when I know it is Safe.
Sun Sep 13, 2015 2:02 pm
