SAR421

Double Stack/Double Feed is superior to Double Stack/Single Feed, this has been a known good design element of submachine guns for almost 100 years. The weak point in double to single is the taper which is an additional friction point and usually the cause of malfunction in the magazine. This has been an issue in high cyclic rate firearms like submachine guns. Additional considerations for a dedicated PCC magazine over a Pistol magazine are that a PCC magazine typically has a curve which also aids in reliable feeding, 30+ round straight magazines like in a pistol are also potential for feeding errors. Also, the feed angle on a pistol magazine is an unnatural reload angle to put the round in the correct presentation to the chamber. A dedicated PCC mag has a natural reload angle relative the the presentation of the round. All that said, I’m sure it will be fine with the JP, they’ve been making a reliable Glock fed platform for a while. I do wish they offered both a Glock and Scorpion mag version though. I’d probably select Glock if I already shot one in competition and Scorpion if I shot anything else.

Awesome, I’ll keep my eye on the matches next time I’m coming down closer.

Yeah, that’s understandable. What range are you hosting matches at? My family has a ranch in Fairfield, southeast of Dallas, I’m usually down that way about once a month.

Here’s another additional video on the system which clearly shows how it functions with diagrams. In a practical sense a direct blowback (most SMG’s) relies entirely on bolt mass and spring force to stay closed long enough which results in heavy cyclical mass moving at high velocity resulting in more recoil. A delayed system (mp5) takes advantage of some method of mechanical advantage to slow the opening with lower bolt mass and spring force with lower cycling velocity resulting in lower recoil.

Hey, I see your profile says you’re in Texas. Any upcoming matches close to OKC you’re planning to go to? I currently just shoot Carry Optics occasionally but looking to add a PCC. I was going to go MPX, but a roller delayed JP certainly sounds like a winner and I’d definitely like to give it a try.

Ok, to be fair that wouldn’t be technologically that feasible. For a roller delay system the upper receiver would need to have appropriate features to interact with the rollers. So at minimum you’d need a new or modified upper receiver and the completely new bolt/carrier. Usually roller delayed systems have a fluted chamber to deal with high extraction pressure as well which is at another modified component. The only technically plausible solution they might offer is to be able to buy a completed upper that would work with your existing lower. Not sure if they’re compatible but it would be possible.

Yeah, it looks like it’s still Glock mag based from the ad as well. Maybe they’ll offer versions in both, although I’d imagine that would require changes to the bolt and lower to accommodate the change. Outside of just reliability, the reload angle is always weird on pistol mag based PCC’s. Purpose built PCC mags are the way to go, Scorpion mags are reliable and cheap. Seems the obvious option. The need to use the same mags for pistol and rifle I think is drastically over prioritized.

I’ll be very interested to see comparisons of this Roller Delayed vs the MPX Gas Piston. I may be the minority but I also wished they changed from Glock mags to something like a Scorpion mag to get a double stack / double feed magazine, which makes far more sense in a PCC. Glock mags have to be angled at an awkward angle to work in a rifle and have inherent reliability concerns over a good double stack / double feed magazine.

That’s really great news, I just put my order in for both. I knew their RMR cut was low, but I didn’t realize it was that low! I hate when people put an optic on a pistol then stick the sights all the way up into the middle of the window. Just enough to peak over if you need them is perfect.

Wait, does that sit low enough in a ZEV slide to use their standard height rears and see the irons through the bottom of the glass? Looking at a ZEV Omen slide and this optic now.