Springer Tuning Projects.

[maximus]

Hi Maxiumus
I'd possibly question increased cocking effort.
My 280 pro with a full length barrel could be cocked by a small child. Effortless, though has had a bit of work to smooth things out.
I think the stroke issue is that the 280 is running near optimum where the 34 being made for higher powers is overspecced and will have a lazier cycle.
Having said that, none of my 3 280's lack power in any respect. And they are all .177. When set up correctly, the 280 needs careful attention to keep safely under sub 12

My 280 is a standard length 177, and I have 34's in std and factory carbine length, both 177. My 280 "is a little stiffer to cock than the carbine 34 and no where near as easy as the std length 34 The 280 was bought 2nd hand and whilst it looked near mint on the outside the piston had loads of holes drilled in it. Power wise I struggled at first but found the breach seal was not working although in good order. I shimmed it up and that has cured it but it's just doing 11 with super domes, less with everything else.
The barrel on mine is the same diameter as the 34's and to me the stock is not inferior to the 34 in any way.

[robs5230]

My 280 is a standard length 177, and I have 34's in std and factory carbine length, both 177. My 280 "is a little stiffer to cock than the carbine 34 and no where near as easy as the std length 34 The 280 was bought 2nd hand and whilst it looked near mint on the outside the piston had loads of holes drilled in it. Power wise I struggled at first but found the breach seal was not working although in good order. I shimmed it up and that has cured it but it's just doing 11 with super domes, less with everything else.
The barrel on mine is the same diameter as the 34's and to me the stock is not inferior to the 34 in any way.

On the power subject.
My pro compact full length has been tuned down to 10.6 with express and domes are 9-9.5 easy to cock
the first K I bought is doing 11.2 with superdomes and just marginally less with express. I think its over sprung.
The second K i have is a sandwell one. Producing 11.7 with express and 11 with superdome. Cocking is easy.

If yours is reading highest with superdome I'd think that its also oversprung and cocking effort could be reduced

[maximus]

On the power subject.
My pro compact full length has been tuned down to 10.6 with express and domes are 9-9.5 easy to cock
the first K I bought is doing 11.2 with superdomes and just marginally less with express. I think its over sprung.
The second K i have is a sandwell one. Producing 11.7 with express and 11 with superdome. Cocking is easy.

If yours is reading highest with superdome I'd think that its also oversprung and cocking effort could be reduced

You could be right, I have contemplated chopping a bit off the spring for that very reason but was bothered about it just reducing the power and being left with a spring that was too short! I added weight back into the piston via a brass top hat and washers, it shoots nice enough though I cant stop the spring from twanging totally despite having tight fitting guides and piston sleeve. Might be a twangy spring or could be a bouncy piston. I may try a different spring one day but all I have in my spring stash are various cut down titan no.1's which all seem to stiff when in and definitely over spring the action. I like the Dianas though and they are usually what I reach for when I want a shot these days.

[Barryg]

On the power subject.
My pro compact full length has been tuned down to 10.6 with express and domes are 9-9.5 easy to cock
the first K I bought is doing 11.2 with superdomes and just marginally less with express. I think its over sprung.
The second K i have is a sandwell one. Producing 11.7 with express and 11 with superdome. Cocking is easy.

If yours is reading highest with superdome I'd think that its also oversprung and cocking effort could be reduced

One thing to look for on Diana break barrels is transfer port barrel alignment especially on .177 as this can affect the performance if part of the TP is blocked by the misalignment, it was years before I discovered this on my 34 all sorted now

[maximus]

One thing to look for on Diana break barrels is transfer port barrel alignment especially on .177 as this can affect the performance if part of the TP is blocked by the misalignment, it was years before I discovered this on my 34 all sorted now

How did you sort it Barry?

[Barryg]

How did you sort it Barry?

I will post some pics after lunch Max, her in doors has just dished it up

[maximus]

I will post some pics after lunch Max, her in doors has just dished it up

Enjoy!!

[robs5230]

One thing to look for on Diana break barrels is transfer port barrel alignment especially on .177 as this can affect the performance if part of the TP is blocked by the misalignment, it was years before I discovered this on my 34 all sorted now

Just checked all 3 of my 280's.
They have a clear witness mark from the breech seal on the front of the cylinder, perfectly centred around the transfer port so I'm good here. Breech seals are correspondingly centred around the bore.

[Barryg]

How did you sort it Barry?

It might be just the old T01s that had the problem, this is my one before and after.
Before
https://imgur.com/cyaaYKn

After
https://imgur.com/2o9WhYc

All I did was to shim the breech face high spots
https://imgur.com/DDbD7AJ

Also my 34 had visual barrel droop before correcting but you can now see no droop
https://imgur.com/6qk95T4

[robs5230]

It might be just the old T01s that had the problem, this is my one before and after.
Before
https://imgur.com/cyaaYKn

After
https://imgur.com/2o9WhYc

All I did was to shim the breech face high spots
https://imgur.com/DDbD7AJ

Also my 34 had visual barrel droop before correcting but you can now see no droop
https://imgur.com/6qk95T4

Ooh, the first pic doesn't look good. Lovely remedial work though.
Diana's are noted to have "inbuilt" barrel droop. Even the sidelevers. Mine luckily dont seem to be affected visually and zero no problem with normal mounts.

[Richvwt5.1]

This thread makes me want a springer to fiddle with

[averageplinker]

I have just acquired an HW98 barrel in .177" to play with

Now shall I put it on my Mk1 HW85 and tune that or do I keep an eye out for some HW80 parts to build a .177" HW80? I am thinking the former rather than the latter.

[robs5230]

You could be right, I have contemplated chopping a bit off the spring for that very reason but was bothered about it just reducing the power and being left with a spring that was too short! I added weight back into the piston via a brass top hat and washers, it shoots nice enough though I cant stop the spring from twanging totally despite having tight fitting guides and piston sleeve. Might be a twangy spring or could be a bouncy piston. I may try a different spring one day but all I have in my spring stash are various cut down titan no.1's which all seem to stiff when in and definitely over spring the action. I like the Dianas though and they are usually what I reach for when I want a shot these days.

Just dropped a 4mm preload washer out of this what I was thought over sprung K. Now doing 11.2 with Express. Not tested domes yet. I have to chop spring now which has compressed coils both ends. Easier to cock and will be even easier yet when sorted. Power will still rise with express.

[look no hands]

I have just acquired an HW98 barrel in .177" to play with

Now shall I put it on my Mk1 HW85 and tune that or do I keep an eye out for some HW80 parts to build a .177" HW80? I am thinking the former rather than the latter.

I'd put it on the 85 as putting it on an 80 would make it almost impossible to lift as they weigh a ton already.

Pete

[maximus]

Just dropped a 4mm preload washer out of this what I was thought over sprung K. Now doing 11.2 with Express. Not tested domes yet. I have to chop spring now which has compressed coils both ends. Easier to cock and will be even easier yet when sorted. Power will still rise with express.

Hmm, might have give my spring the chop then! Currently it's the factory item but with the extra preload of the top hat and thrust washer.