I have tried two versions of the Alatros in my S400 ( no breath hole needed ). The 2nd one was better but in the end I took it out. I just put a Huma in my R10 MKii .22 as the original had started playing up and so far very impressed, 7 ft/s max spread over 100 shots and very efficient as I had to remove all the delrin preload that I had machined for the hammer spring to make the gun legal, I got it from XTX and I believe he had set the pressure to 75 bar.
A.G