Tuning Modified/ported hatsan valve housing question

[Long_Gun_Dallas]

I know a number of guys have ported their valve bodies on the at44, flash, bt65, or nova.

What I'm wondering is if it had a negative affect on the power curve....

I had about a 70 shot flat spot on my Novastar shooting 12gr slugs for 880fps, but they don't shoot so hot at those speeds. Althout jsb monsters do, I know the slugs like 1030 or so fps 

 

[Odoyle]

Assuming yours is a factory rated 37fpe 177 Something seems to be up with your gun since you should be able to hit 1050+fps with 12gr slugs unless they are too oversized.

 

[Long_Gun_Dallas]

I detuned it, because the barrel was shooting all over the place. Thorough polishing took care of that.



But I didnt polish until after I had detuned it (because of hatsan debounce mechanism gouging receivers) mine was starting to see some damage from less than 200 shots. I also caliber converted to .22 and shot 14.3 chps very happily at 880fps from a 15" barrel.



Also, my barrel port was very poorly aligned on the .177 so maybe some turbulence was at play? I did fix that at the same time I polished it. I know porting will help flow in the valve housing... But I don't know if the hindered flow there is keeping the power curve desirably flat.



I know %100 that the valve seal/seat and stem sizing is playing a large role in keeping the power curve flat. But I don't know if going to a single aligned port instead of the many periphery ports in the valve housing will harm the flat power delivery.



I'm planning to up the power, so the porting is not necessary, but should help run less hammer... But I really would like to know if it will be detrimental to the overall useable shot count.

 

[Butch]

Dallas, there is excellent write up on what you are wanting to know on GTA by rsterne (Bob). Subsection “Bob and Lloyd’s workshop”. 
Butch

 

[Butch]

Hatsan AT44-10 long in .25 is the subject to look up. 
Butch

 

[Long_Gun_Dallas]

Cheers, and thank you!

 

[Butch]

You’re welcome, and that was the guide I used on my NovaStar considering the Star is based off the AT44 platform. I did not do the valve though, but thought hard about it and still may. 
Butch

 

[Long_Gun_Dallas]

From the data I saw, it looked like getting rid of the periphery ports, and going to single did increase efficiency... But also created more of a curve in the power delivery... So, not what I'm looking for. Thanks again!