So much for not tinkering!
Having spent a few weeks very much enjoying the Vet 2 .22 Tact, it became clear that it quickly hits a wall in terms of power at around 55fpe. Bumping up the reg and hammer does very little above 50fpe because, in short, the valving is a major impediment.
I’m not looking to turn it into a hotrod, but would like to get it into a state to shoot the Zan 28g slugs at 900fps without starting to strain the system with excessive hammer. One method would be to open up the brass valve, but I’ve heard that they’re quite fragile, so I opted to do a peek poppet with a stem that’s thinned close to the poppet surface.
Not having access to a decent lathe, the major challenge for me involves the drilling and placement of the stem, but I overcame this by making a 3D printed drilling jig that put the hole in the poppet dead center. I then reused the stem from the original poppet (which popped off far too easily for my liking), after reducing its diameter to 2mm (from 3) in the 10mm long section behind the poppet face. This effectively opens the valve throat area. The stem was then tapped into the peek and the poppet was shaped on my crappy mini lathe. The OD was reduced from 7.7mm to 7.5mm. I then surfaced the poppet face using another 3D printed jig that allowed fine sanding, culminating in 6000grit 3M cloth. It sealed right away and has been holding pressure for over 4 days.
The theory here is that the PEEK poppet opens more easily because there is less compression of the seal to overcome, so less hammer is needed to open the valve. In addition, the throat is opened by the reduced oD of the stem, allowing more flow.
The gain here isn’t huge and wasn’t intended to be - around 30fps peak at the same reg pressure of what’s estimated to be 140bar. However, I no longer need to use any shimming of the hammer spring and have the added bonus of a quieter hammer. The modest increase in power is enough to allow the gun to be in a comfortable spot shooting the Zan 28 at a speed of 905fps. I don’t know if it’s due to reg settling or this new PEEK poppet, but the ES is now down at 2!
Since getting the Mora 22, which is shooting 40g Altaros at 900fps without even breaking a sweat, I’ve decide to dedicate the Vet 2 towards shooting these .217 28 grain hollow point Zans, which it seems to shoot just as well as the Altaros. The cost are lower for one, but more importantly, I’m not so worried about the downstream consequences of pass through.
With this less edgy tune and stupidly low ES, the Vet 2 is astonishingly accurate. The RTi Mora is also fantastic but not as easy to shoot accurately, at least for me. Here’s a target from this morning at 80yards where I lost count of the number of shots and still got CTC ~1 inch. It’s still not a pretty gun but the shot cycle and ergos are fabulous…