Help with Hw97 compression chamber.

[elewis411]

Hi guys, I’ve got a Hw97 which somebody has modified by milling slots in the piston bringing the weight of piston and v Mach seal to app 220 grams which going by posts on the bbs made by some very knowledgeable people is a good weight, the transfer port of the compression cylinder seems to be 4.2mm or so measured in not the best way but the best method I have available by inserting a drill bit, 4mm is lose, 4.5 won’t fit, is the tp diameter too large? and if so is there anyone amongst us who could sleeve it for me as it’s way beyond my capabilities, the spring has 29 coils and there is no preload on the back block also piston seal feels quite tight , set up like this the rifle is 7.5 ft/lbs and feels quite harsh, I would obviously pay the proper rate for this work…Thanks…Lewis…

[Shed tuner]

Hi guys, I’ve got a Hw97 which somebody has modified by milling slots in the piston bringing the weight of piston and v Mach seal to app 220 grams which going by posts on the bbs made by some very knowledgeable people is a good weight, the transfer port of the compression cylinder seems to be 4.2mm or so measured in not the best way but the best method I have available by inserting a drill bit, 4mm is lose, 4.5 won’t fit, is the tp diameter too large? and if so is there anyone amongst us who could sleeve it for me as it’s way beyond my capabilities, the spring has 29 coils and there is no preload on the back block also piston seal feels quite tight , set up like this the rifle is 7.5 ft/lbs and feels quite harsh, I would obviously pay the proper rate for this work…Thanks…Lewis…

it's a bit too big, but not crazy.. you may get it shooting reasonably at that size, especially if it's a 26mm tube. 3.5-3.8mm would be better. Check the breach seal isn't leaking. Also sticking in a decent spring to get the power up is likely to make it shoot nicer. keep the seal tight for the moment, as it;s reduce some of the harshness if the TP is <much> too big.

[madcarlos]

Hi guys, I’ve got a Hw97 which somebody has modified by milling slots in the piston bringing the weight of piston and v Mach seal to app 220 grams which going by posts on the bbs made by some very knowledgeable people is a good weight, the transfer port of the compression cylinder seems to be 4.2mm or so measured in not the best way but the best method I have available by inserting a drill bit, 4mm is lose, 4.5 won’t fit, is the tp diameter too large? and if so is there anyone amongst us who could sleeve it for me as it’s way beyond my capabilities, the spring has 29 coils and there is no preload on the back block also piston seal feels quite tight , set up like this the rifle is 7.5 ft/lbs and feels quite harsh, I would obviously pay the proper rate for this work…Thanks…Lewis…

I would replace or check the breach seal before going any further, 4mm seems a little big on the port hole , Not sure what standard is but normally a little bigger can improve but to big is not ideal,

[elewis411]

Thanks very much for the reply, your knowledge is much appreciated…

[elewis411]

I would replace or check the breach seal before going any further, 4mm seems a little big on the port hole , Not sure what standard is but normally a little bigger can improve but to big is not ideal,

Thanks for that, got a breech seal on order…

[elewis411]

Don’t know if it makes a difference but the rifle is .177 and 26mm…Thanks…Lewis…

[Shed tuner]

Don’t know if it makes a difference but the rifle is .177 and 26mm…Thanks…Lewis…

that's the most sympathetic combination for a somewhat overly large TP...

[deejayuu]

Shaun is in Swansea. He'll sort it.

[madcarlos]

Thanks for that, got a breech seal on order…

No probs bud, I've just renewed one of my old 77s internals and overlooked the breach seal, Made a hell of a difference once renewed,

[elewis411]

Shaun is in Swansea. He'll sort it.

Thanks for that, I remember buying one of his rifles a few years back, do you have e contact details…Thanks…Lewis…

[deejayuu]

Check PM

[elewis411]

Check PM

Thanks for that…much appreciated…