Skipper the inside of the barrel is grooved in the same way as the picture of the later marked Flare pistol one I am seriously looking at but the cost is almost prohibitive, as you said these are not easy to come by : especially the Z Kampfpistol. used different flares-flare-grenades, there are several different types that could be even used for knocking out recon light vehicles like jeeps. as the case of Nicks well preserved example with the grooves the round spun in like fashion. I've got a ton of info hidden amongst all then files.........