My Urutau was a big hit at the range today. ROs and shooters alike were all very interested in the build and how it performed. I've been slowly working to get the firing pin length dialed in and I think I'm finally getting close. I didn't run a lot of rounds, but it ran the two 20-round factory CZ mags and the two 30-round ETS mags I brought without a single failure. Some slow-fire, some doubles, some Bill-drills. I even ran the last 30 rounds with a 3D printed can (OKB-69 Khrizantzema). Note that this is with a remixed lower receiver since the ETS mags do not properly fit the lower in the official release. If I have another successful range session with this lower, I'll release it.
How good is that suppressor compared to bulkier ones like the FTN?
Not nearly as quiet as a big can like the FTN, but I don't have any way to quantify. It does take some of the "edge" off but it's not hearing safe. If I had to guess, it brings the 9mm down to about the level of an unsuppressed 22LR, so probably a 10 - 15 dB reduction.
The advantage the Khrizantzema has is that it's a flow-through design so you get a lot less backpressure than a traditional baffle can like the FTN series. On simple blowback PCCs, that beats up the gun less (you don't get a big increase in bolt opening velocity) and puts less additional gas out the ejection port. On a bullpup like the Urutau where your nose is literally right above the ejection port, that's a big win.
Sweet build, thanks for the quality info as well!