Hi, I’m new to the board. I’m mostly a C&R semi-auto collector, and a recent purchase brings me here. I picked up a 4MM barrel for an Astra 300 that looks to take 4MM M20 cartridges with an adapter of some sort. I found a thread on this site that seems to picture what I have: viewtopic.php?f=8&t=6647&start=45
Here are photos, including on showing what I believe it the adapter cartridge (from this site).
Am I correct, and does anyone know where I could purchase a few of the adapter cartridges?