Tuning A Visual Representation of Piston Bounce/Weight vs Hold Sensitivity and Accuracy

[Sqwirl57]

Ok so messing with full power tunes for a .22 springer here. I was already inside the gun modifying the trigger housing to accept a better spring guide and decided to swap the heavy 55g top hat for a lightweight 10g top hat. Got it back together and took a few shots down range to settle it in and then moved to paper because it felt pretty good.

Red circles: 10g top hat, front bag only. Holy f.... I think there's something wrong here.

Moved to the Orange circles: 10g top hat, artillery hold with hand between front the bag and stock. Better. Nothing wrong with the barrel, the gun is just hold sensative. Very hold sensative. Let's put that 55g top hat back in and see what happens.

Green group: 55g top hat, front bag only. That's better. One low shot but thats definitely better. Amazing what a 45g/0.1lb/1.6oz can make

Long story short, sometimes the manufacturer knows best lol. Still worth the experiment though and I may try again and meet in the middle to see what happens.

 

[A.G.R]

Added mass can be benificial in taming recoil actually. When balanced with the port size and stroke..
longer stroked guns need more weight and pre load.

hw 80 is not a long stroke gun. Hw 95 is and is a bit testy with light wire. People talk about it being a mini R1 when it’s as far from it as can get.

 

[Sqwirl57]

Added mass an be benificial in taming recoil actually. When balanced with the port size and stroke..
longer stroked guns need more weight and pre load

hw 80 is not a long stroke gun. Hw 95 is and is a bit testy with light wire. People talk about it being a mini R1 when it’s as far from it as can get.

Yessir that's the lesson learned here for sure. All said and done and that 40g reduction really didn't feel that all that much better all said and done.

 

[beerthief]

what if you add instead of subtract G's ? smaller amounts 5 g ?

 

[Sqwirl57]

what if you add instead of subtract G's ? smaller amounts 5 g ?

That is on the list as well although but I need to get some material to work with

 

[Nitrocrushr]

Yessir that's the lesson learned here for sure. All said and done and that 40g reduction really didn't feel that all that much better all said and done.

Sqwirl57, yeah it’s a balancing act for sure. I recently had a customer send me an extremely hold sensitive TX200 .177. His goal was to optimize grouping at 50 yards. As it arrived it would not even group at 30 yards. Like you I also reduced mass weight by going with a delrin tophat. But I also swapped to a lighter spring and machined a new transfer port. End result was a rifle that was much more manageable without any special hold.

The rifle ended up at 13.5fpe.

 

[fishing43]

Ok so messing with full power tunes for a .22 springer here. I was already inside the gun modifying the trigger housing to accept a better spring guide and decided to swap the heavy 55g top hat for a lightweight 10g top hat. Got it back together and took a few shots down range to settle it in and then moved to paper because it felt pretty good.

Red circles: 10g top hat, front bag only. Holy f.... I think there's something wrong here.

Moved to the Orange circles: 10g top hat, artillery hold with hand between front the bag and stock. Better. Nothing wrong with the barrel, the gun is just hold sensative. Very hold sensative. Let's put that 55g top hat back in and see what happens.

Green group: 55g top hat, front bag only. That's better. One low shot but thats definitely better. Amazing what a 45g/0.1lb/1.6oz can make

View attachment 418039

Long story short, sometimes the manufacturer knows best lol. Still worth the experiment though and I may try again and meet in the middle to see what happens.

Thanks for sharing your experiment with us. Great info.

 

[boscoebrea]

Airgun World volume 45 issue 3 article on "The Pellet Effect",Jim Tyler helps explain some things that may help you.

 

[Sqwirl57]

Airgun World volume 45 issue 3 article on "The Pellet Effect",Jim Tyler helps explain some things that may help you.

I can't seem to find a copy. Know of any good places to look?

 

[Mycapt65]

Thanks for posting. I like that you're documenting your findings with targets. Adding piston weight via large steel top hats was popular several years ago. It seems the few kit makers out there have switched to making them out of Delrin now. I'm not sure if the move away from the steel was simply a labor reducing move.

A lot of accuracy not only depends on reducing piston bounce but the back pressure that causes that bounce. One spring top hat combination may not be accurate with one pellet as it is with another. It's a fine balance of forces. Sometimes after tuning a gun it changes it's favorite pellet because the cycle is better with a different pellet.

I don't have access to a lathe anymore so I'm stuck with the usual tune kits suppliers. I do experiment with adding thick steel washers over the top hat. So far I haven't seen any increase in power that the additional preload couldn't account for.

Keep us informed of your experiments. Just remember if you change pellets you may have to change your spring /top hat combinations. The whole thing is enough to make one nutty.

 

[boscoebrea]

I have the magazine,It might help to look up Jim Tyler,he is a springer gura from England,his work is far too much for me,but for you ,his work may save you some time and give you a faster base to follow.The thing is that it is all relative in the respect of Newtons law,every reaction has another reaction,yes ,I know I changed the reaction thing.
My thought is to put more mass to the piston....and remember the size of the orifice,Mr. Tyler has used different size orifices to match what he is trying to=match the best grouping pellet for said rifle and get the best possible shot cycle he can for that pellet.
I guess he is trying to get the very best possible outcome.
Another thing he has done is to shorten the stroke of his air rifle.
I am mentioning this stuff because you are interested in experimenting with your springers and his work and ideas my help you with your ideas.
Bottom line is many of us welcome your work and ideas

 

[bustachip]

Ok so messing with full power tunes for a .22 springer here. I was already inside the gun modifying the trigger housing to accept a better spring guide and decided to swap the heavy 55g top hat for a lightweight 10g top hat. Got it back together and took a few shots down range to settle it in and then moved to paper because it felt pretty good.

Red circles: 10g top hat, front bag only. Holy f.... I think there's something wrong here.

Moved to the Orange circles: 10g top hat, artillery hold with hand between front the bag and stock. Better. Nothing wrong with the barrel, the gun is just hold sensative. Very hold sensative. Let's put that 55g top hat back in and see what happens.

Green group: 55g top hat, front bag only. That's better. One low shot but thats definitely better. Amazing what a 45g/0.1lb/1.6oz can make

View attachment 418039

Long story short, sometimes the manufacturer knows best lol. Still worth the experiment though and I may try again and meet in the middle to see what happens.

I think I need to try something similar with my 77K that doesn't shoot very well. I made a O-ring piston seal out of delrin, maybe I need to try one out of steel or aluminum.

 

[GoldenStateAIRGUNer]

what if you add instead of subtract G's ? smaller amounts 5 g ?

That is my thought as well.

 

[A.G.R]

I have the magazine,It might help to look up Jim Tyler,he is a springer gura from England,his work is far too much for me,but for you ,his work may save you some time and give you a faster base to follow.The thing is that it is all relative in the respect of Newtons law,every reaction has another reaction,yes ,I know I changed the reaction thing.
My thought is to put more mass to the piston....and remember the size of the orifice,Mr. Tyler has used different size orifices to match what he is trying to=match the best grouping pellet for said rifle and get the best possible shot cycle he can for that pellet.
I guess he is trying to get the very best possible outcome.
Another thing he has done is to shorten the stroke of his air rifle.
I am mentioning this stuff because you are interested in experimenting with your springers and his work and ideas my help you with your ideas.
Bottom line is many of us welcome your work and

I think I need to try something similar with my 77K that doesn't shoot very well. I made a O-ring piston seal out of delrin, maybe I need to try one out of steel or aluminum.

I have tried both, O ring shot cycles are not for me. I’ve experimented in low power to 30 ft lb guns with them
they feel like a snappy end blow cycle

I run cup faced seals in every gun I own as they work with how I Tune. A loose seal is a bad seal for my work ..

 

[bustachip]

I have tried both, O ring shot cycles are not for me. I’ve experimented in low power to 30 ft lb guns with them
they feel like a snappy end blow cycle

I run cup faced seals in every gun I own as they work with how I Tune. A loose seal is a bad seal for my work ..

Funny thing is my 97K with an aluminum O-ring seal will stack pellets no problem. What does your cup faced seal look like?
Is it similar to the prosport seal?

 

[A.G.R]

Funny thing is my 97K with an aluminum O-ring seal will stack pellets no problem. What does your cup faced seal look like?
Is it similar to the prosport seal?

It’s not a accuracy issue it’s a shot cycle feel ..

also the 97/77 platform is center transfer port design with a much shorter length. It has a much different potential

 

[bustachip]

Yes my 77K is a snappier cycle, I need to try something different with it.

 

[Nitrocrushr]

Part of the balancing act in tuning is to tune for forgiveness. While you can tune rifles for good groups, that does not necessarily translate into a repeatable POI. Shooting at various spots all around the target might reveal a different POI as you move from spots at the top vs spots across the bottom. You might see POI on bottom spots take a 1/4” shift. Still group tight, but shift POI from your point of aim. Its that balancing act with numerous things coming into play. Piston bounce, velocity, rifle movement and timing of pellet exit from barrel. Adding to this is muzzle movement at the time of pellet exit. Was muzzle in the midst of a swing or was it at a stopping point. All part of the game

 

[bustachip]

Part of the balancing act in tuning is to tune for forgiveness. While you can tune rifles for good groups, that does not necessarily translate into a repeatable POI. Shooting at various spots all around the target might reveal a different POI as you move from spots at the top vs spots across the bottom. You might see POI on bottom spots take a 1/4” shift. Still group tight, but shift POI from your point of aim. Its that balancing act with numerous things coming into play. Piston bounce, velocity, rifle movement and timing of pellet exit from barrel. Adding to this is muzzle movement at the time of pellet exit. Was muzzle in the midst of a swing or was it at a stopping point. All part of the game

Yes trial and error and lots of shooting. Then throw in springer shooting abilities and if one wears glasses..lol.