Q: Does the last round bolt hold open work?
A: Glock magazine followers will not interface by themselves with the bolt catch. For last round bolt hold open to work you need an upper with a linkage system such as those made by New Frontier Armory, Gibbz, or Aero.
Without a linkage you can use the bolt catch as a manual lock open feature for administrative tasks like showing clear on a range.
Q: Will the KP-9 Work with the CMMG Radial Delayed Upper?
A: Not without modifications that you will need to perform at your own risk. The ejector would need to be modified or removed and the magazine catch modifed to make the mags sit at a different height.
If you want to use a CMMG radial delayed upper with one of our polymer lowers we recommend you do it with the KP-15 and CMMGs PMAG conversions to 9mm.
Q: Why Glock Mags?
A: Glock magazines are plentiful, cost effective, and work reliably.
Q: Will you do a Colt Mag version?
A: No we do not intend to. I would require an entirely new mold.
If you want to use Colt mags with one of our polymer lowers we recommend using a KP-15 with a Hahn-Precision magazine block.
Q: Will you do a Scorpion Mag version?
A: No we do not intend to. I would require an entirely new mold and dedicated uppers that would allow the scorpion mags to sit high enough into the upper.
Q: What buffer should I use?
A: 9mm Blowback systems require a minimum of 5.4oz to avoid damaging the lower. The heavier the buffer you can use the better as long as the firearm cycles and ejects reliably. While the tube is carbine length, because 9mm cartridges are shorter than 5.56mm, extended buffers can be used to add weight and shorten the stroke of the bolt group.
Systems like the JP SCSS can also be used.
DO NOT use flat wire springs or buffers with sharp edges as they can damage the buffer tube.