I've seen the future....

[bigtoe01]

A HW 25 spring mght be just about right with those little pistons if the data on the spring thread is right.

I will just have springs wound to what we need....i have some that are close already, and getting more done is not an issue.

[greenwayjames]

If you use the Bowket design made to use mostly Titan components and shown in one of his AGW articles you can get as small as you like on piston effective frontal area without any restriction on mainspring dimensions. The compression chamber is sandwiched between the trigger and the spring. The spring is at the front of the rifle in a seperate compartment. Have a look on the JB Fanpage. The article is in there

[bigtoe01]

If you use the Bowket design made to use mostly Titan components and shown in one of his AGW articles you can get as small as you like on piston effective frontal area without any restriction on mainspring dimensions. The compression chamber is sandwiched between the trigger and the spring. The spring is at the front of the rifle in a seperate compartment. Have a look on the JB Fanpage. The article is in there

Thats too complicated, i can go down to 20mm piston very easy, keeping it simple also keeps the cost down also, the only issue will be spring wire diameter...which again is solvable by having a new spec spring wound up.

[NickG]

I'm sure you are right, however I've already noticed that 23mm is much more prone to combustion, presumably due to the higher pressures... I'm thinking that this will start to be a problem if you go too small, esp on .177.

On .20 & .22, not anything like such a big issue...

Briefly tried it on my .20 and it was surreal

The combustion problem is what I have been going on about, have some tube ordered going to try 21mm, in my 77, the hc shoots well at 23mm but not better than my 25mm set up, so still playing about

[NickG]

well due to lack of workshop/lathe [theres only so much i can do with a cordless-spinning-a-piston and hand tools] i am still hoping one of you guys comes up with a drop-in kit for the 97 and 95/98 .
for the 95/98 i think a piston extention to short stroke and tophat/guide would be a good starter kit [put my name down for one please] . and for the 97 a pre-made sleeve [ready to self install] a smaller diameter piston [new latch rod for rotating purposes] and maybe a new trigger sear if needed, again with guides as an option. put me down for one of those too

Clip on poly head

[slugger]

i would prefere an ally head extention for the 98 ...... then i can simply refit my hw seal [easyest method to short stroke me thinks] ?

[NickG]

i would prefere an ally head extention for the 98 ...... then i can simply refit my hw seal [easyest method to short stroke me thinks] ?

problem with ally is the area for grub screws is a bit thin, so I do mine by tapping the nose of the piston and use a countersunk screw

http://i1346.photobucket.com/albums/...psophhpmz7.jpg

[Gecko]

i would prefere an ally head extention for the 98 ...... then i can simply refit my hw seal [easyest method to short stroke me thinks] ?

Ive been very happy with the poly head on my HW97 even with the shorter stroke with the oring seal the power increased over the HW seal at standard stroke.
The poly head has been fitted for quite a while now and no issues so far, very consistent over the chrono.

I want to knock 5mm to 6mm of my HW98 probly going to go the Poly head route, my HW95 has a delrin head with oring seal and that shoots mustard i feel the delrin head lands harder then the poly head.

[slugger]

nick, is the grubscrew issue due to the 'head' of the piston [the lip that the seals clips onto] being quite wide ? in other words could a nice ally head-extention with grubscrews work if the piston-lip was machined down/away ?
im very keen on an ally jobbie as i have one on my prosport and it works perfectly........and as i have the new style hw seal im keen to re-use it on said extention
i would be able to lose the lip myself and then fit the extention without the need to send-away my piston if you see what i mean

[busanga]

So if all this sleeving down etc makes the guns so much better, why don't the manufacturers just do it themselves ?

[slugger]

well they could make all their model range super efficient sub 12 for us uk shooters...and then make bigger-bore / longer stroked versions for export to other countries where much higher ft/lbs is the norm...
or.....
they could save them selves a bloody fortune and simply build one gun capable of big power and then cut the spring in it to keep it sub 12 for the uk market resulting in a lazy/slow/hold-sensitive firing cycle........
which option do you think they chose ?

[NickG]

nick, is the grubscrew issue due to the 'head' of the piston [the lip that the seals clips onto] being quite wide ? in other words could a nice ally head-extention with grubscrews work if the piston-lip was machined down/away ?
im very keen on an ally jobbie as i have one on my prosport and it works perfectly........and as i have the new style hw seal im keen to re-use it on said extention
i would be able to lose the lip myself and then fit the extention without the need to send-away my piston if you see what i mean

That would give more material, but you wont be able to return to standard, The screw in the end sorts the problem and it can be returned to standard,
If you have access to a lathe tapping the piston 5mm is a 10 minute job

[slugger]

thats the issue, i dont anymore i could do it by hand but i know if i get the drillbit 'walking' even a fraction of a mm im going to end up with the extention sitting off-centre .......grr
so for that reason i wouldnt mind not being able to go back to standard.......and i know i can machine-off the lip almost perfectly with the piston spinning in the cordless and a slitting disc to size-down [sound scary i admit, but its actually very neat and accurate]
and if there was a tiny weeny off-centre discrepancy i could easily correct it by using the 3 grubscrews to centralise the extention
so....... when can you make me an extention, and what stroke reduction [extention thickness] is recomended for a 95/98 ?

[Black Beard]

An interesting thing happens on sub-20mm pistons. They can fit inside the spindle of a standard Chinese lathe. The world becomes the home tinkerer's oyster.

[bigtoe01]

An interesting thing happens on sub-20mm pistons. They can fit inside the spindle of a standard Chinese lathe. The world becomes the home tinkerer's oyster.

LOL...im lucky i can get quite a bit bigger in my Chinese lathe here...