sleeving versus stroking....

[greenwayjames]

Yeah i heard the same story from another source. One direction we are going different to Bowkett is piston weight, he favours heavy pistons, where we are going light weight.

He didnt mention piston weight but my guess is reduction of it was probably one of the reasons for experimenting with small diameter pistons. It doesnt make sense to suggest he would automatically use heavy pistons because he "favours" them. Whatever he used it certainly worked.

[bigtoe01]

He didnt mention piston weight but my guess is reduction of it was probably one of the reasons for experimenting with small diameter pistons. It doesnt make sense to suggest he would automatically use heavy pistons because he "favours" them. Whatever he used it certainly worked.

going by his tune on the 77 he documented in AGW and the gun we all shot he tuned at the boinger bash I came to the conclusion he would use a heavier piston...

Either way, 23mm works, 7/8th is 22.7 so near enough the same.

[greenwayjames]

going by his tune on the 77 he documented in AGW and the gun we all shot he tuned at the boinger bash I came to the conclusion he would use a heavier piston...

Either way, 23mm works, 7/8th is 22.7 so near enough the same.

JB hasnt done any spring airgun conversion for at least twenty years so unless he recently serviced the 77 you shot at the Boinger Bash it isnt really representative of his work. His conversions were not DIY servicable even by experienced bodgers. Having said that, how can conclusions on what was inside a one off experimental air rifle that you have never seen or used be drawn by shooting a HW?
Either way 7/8" worked in the rifle I was allowed to shoot so we can agree on that

[bigtoe01]

JB hasnt done any spring airgun conversion for at least twenty years so unless he recently serviced the 77 you shot at the Boinger Bash it isnt really representative of his work. His conversions were not DIY servicable even by experienced bodgers. Having said that, how can conclusions on what was inside a one off experimental air rifle that you have never seen or used be drawn by shooting a HW?
Either way 7/8" worked in the rifle I was allowed to shoot so we can agree on that

you talk like you are Bowkett...are you?

either you are him or you are a stalker...which is it?

[greenwayjames]

you talk like you are Bowkett...are you?

either you are him or you are a stalker...which is it?

No but I've had a Stalker - it was an FAC Leopard. Very nice. 920fps .22" Bis Mags. The bunnies celebrated the day I moved it on to make room for another goodie on my ticket

BTW do you know JB? You seem pretty sure of what he did and didnt do. I assume you are a drinking buddy of his?

[vobster]

No but I've had a Stalker - it was an FAC Leopard. Very nice. 920fps .22" Bis Mags. The bunnies celebrated the day I moved it on to make room for another goodie on my ticket

BTW do you know JB? You seem pretty sure of what he did and didnt do. I assume you are a drinking buddy of his?

Strange that your name is also john.

[Shed tuner]

JB hasnt done any spring airgun conversion for at least twenty years so unless he recently serviced the 77 you shot at the Boinger Bash it isnt really representative of his work. His conversions were not DIY servicable even by experienced bodgers. Having said that, how can conclusions on what was inside a one off experimental air rifle that you have never seen or used be drawn by shooting a HW?
Either way 7/8" worked in the rifle I was allowed to shoot so we can agree on that

JBs work on springers is well documented to generally include adding a lump of weight to the piston.
Now I'm not saying that's "bad" per se, in as much as it will often help efficiency. However it can also somewhat increase recoil. But the real potential downside is that the shot cycle isn't so nice, feeling slammy. This almost certainly won't have any affect on accuracy, as per the other thread you started and we answered about when the pellet leave the barrel in the cycle, but it does mean the second fwd stroke of the piston crashes somewhat unpleasantly. It may even enhance accuracy, as the piston will decelerate more slowing at the end of the first fwd stroke before bounce back.

Ref the example above, 30 years may have passed, but I doubt the weight of the piston or the size of the transfer port has magically changed by itself in that time

I'd also say that the guy did some great work on springer tuning, but the "addi ng weight to the piston" direction was a bit simplistic IMHO.

I'd also read of his 7/8" cylinder gun - wonder why it never made it to "production" ? Can you ask him next time you call him?

[greenwayjames]

I'd also read of his 7/8" cylinder gun - wonder why it never made it to "production" ? Can you ask him next time you call him?

I will.

[greenwayjames]

I'd also read of his 7/8" cylinder gun - wonder why it never made it to "production" ? Can you ask him next time you call him?

I put your question to him in a phone call earlier this morning.
He said that it was first made about 1982 as an experimental jig in a search of knowledge about the effects of using different diameter pistons and stroke lengths. It was never intended for production. It was in fact a 1" diameter piston model that could be reduced to 3/4" via 7/8" could also use different stroke lengths. The version I tried was in 7/8" diameter and was perfect for 12 ft/lbs use. At the same time he went to the other end of the scale and made another rifle to find out the results from a very large (1 5/8" diameter) piston using an extremely short stroke.
At the end of the 1980s he made a unique spring air rifle for Titan using many parts from the Manitou, Mohawk. This again never went into production as he left Titan but used a very small frontal area piston but in a diffent way to the earlier one. Normal size air rifle springs could be used. It was an unusual layout with the spring at the muzzle end with a piston having the sear rod passing through the compression cylinder end wall to engage a trigger closest to the butt. The compression cylinder was sandwiched between the spring and trigger unit
This information was shared with other airgunners via an article in Airgun World and more recently details of it was put up on the Facebook Fanpage for John Bowkett

I hope this answers your query

[POK!]

how can conclusions on what was inside a one off experimental air rifle that you have never seen or used be drawn by shooting a HW?

Sometimes BBS'ers like to think they're inventive and pioneering. Point out it's been done before, often decades ago and they'll try and rationalize things so their ideas are still novel. There's always room for improvement but the implication "Bowkett was wrong" is unnecessary but fairly typical unfortunately.

[vobster]

What a shame JB didnt get his 7/8 into production, set springers back twenty years!

But then he was always in it for the money, where as the open knowledge of the bbs tuners is to the benefit of all. Because information was not shared, it needs to be rediscovered.
Of course, the benefit of the rediscovery is that its done in the open without an agenda, and we can share and learn from each other, giving a better result in the end.

[NickG]

What a shame JB didnt get his 7/8 into production, set springers back twenty years!

But then he was always in it for the money, where as the open knowledge of the bbs tuners is to the benefit of all. Because information was not shared, it needs to be rediscovered.
Of course, the benefit of the rediscovery is that its done in the open without an agenda, and we can share and learn from each other, giving a better result in the end.

Research and development is faster and more effective when done by individuals, and then shared, the more people that are involved the better it gets, and there are no constraints so who knows where it will go, exciting. imo

[TonyL]

Just a quick thought, chaps, to see how relevant this may be.....

Once correctly set-up, I think it was mentioned above that the narrow bore gun would be less impeded by friction.

But, also, with the narrow bore / longer stroke, would this set-up produce higher cylinder temperatures, which would also aid efficiency, providing the air with more energy?