HMO pistons and the Diana TH56 in .177 and .22

[JSR:.]

I posted this in another forum, the dianawerk collective. Thought members here would be interested too. Its about the performance in my th56's when using the HMO pistons sold by Hector Medina...


Ok... a few weeks ago Hector announced he had several HMO pistons on hand. I got in line for two if available after he gave a fair time to those already waiting. Well I got mine and this past weekend installed them. I have two Diana's in the TH56 platform with vorteks on both of them. With the vorteks in my .177 jsb heavy's launch at 860 to 870 fps and in my .22 predators launch at 740 - 750. I was really looking to push my .22 to launch predators in the 800+ range and just experiment with my .177. The original spring in the .22 launch predators at around 720 - 730 fps so the vortek was an improvement in both power and handling, but still not were I felt the Diana could deliver.

First the .22...

After installing the HMO piston, crony it with predators which are one of my favorite pellets and one that shoots extremely well in the th (the other one is Crosman premiers). A 50 shoot string registered 810 - 825 fps with a mean of 817. Darn good! Now, there was something else that I didn't count on. The already minuscule recoil of the 54/56 mechanism became even less noticeable! I mean, more than a few times I had to look at the crony thinking it didn't shoot. I believe the extra mass of the piston helps tame even more the spring recoil in this platform.

Second, the .177

With the vortek kit jsb heavies launched at 860-870. With the HMO piston jsb's were launching at 810 - 815. A decrease in speed but the same effect on the recoil, almost nil. In this one I went back to the original piston being I want to keep it shooting at the increased speed it had with the vortek. Curiously in this Diana the original spring launched the jsb's a bit higher, 880+ but the vortek did improve by quite a bit the spring twang and still kept the jsb's shooting well.

I believe this info should translate to the 54 platform too. I am quite happy with the results...





JSR:.