Well, finally made it down to the range today. Luckily only a 35min drive. Forgot to take a magazine with me so only could check my Noveske Flaming Pig will allow bullets to pass through it... Since I didn't have a mag I couldn't even check for last round hold open. There are some reviews on this website which state this device does create some back pressure:
https://www.primaryarms.com/noveske-...2x28-nvkx3556p
This isn't where I bought mine and don't really know much about primaryarms so not endorsing them really. Also of course, mine is a 5/8x24 so basically this one:
https://www.primaryarms.com/noveske-...x-24-threading
I also brought a single shot TC pistol with me to test out the new 18" 223 Wylde barrel on it so at least the trip wasn't wasted totally.