Underpowered Hw77 .22 Problems.

[ArcticWolf 7]

I reckon someone on this forum may be able to help, so here goes.

 

I recently bought an older 25mm second hand HW77.22, in good nick, stripped it, cleaned inside the piston, barrel and chamber, fitted a new Breech Seal, and Piston Seal, from Welsh Willy, and chrono'd it on the mobile light chrono app only for it be reading about 447fps or 7ft/lb of muzzle velocity. Using JSB Match 15.89gr pellets.

 

Im not particularly clued up on air rifles. Havent shot one for years. But want to get it up to about 10.5 -11.5 ft/lbs.

 

Could the chrono app be wrong?

Could it be the spring? I suspect this is the original one, but nothing is obviously wrong with it.

Should I try adding some washers on the mainspring guide?

 

Dont want to spend a huge amount of money on it. [it's gonna end up costing me more than its worth to send it off for a full V-mach service.]

 

What would you do?

 

Whats my next move?

 

Ta. Dave.

Edited December 4, 2012 by ArcticWolf

[toby63 1,236]

you shud of put new spring in it when you had stripped it down.

[carp man 1 219]

you shud of put new spring in it when you had stripped it down.

[Sjt657 191]

Read the reviews on the app most say its good ... But look at the ones who compare it they say its not accurate

[ArcticWolf 7]

I might pop over to a gunsmiths/shop, like Henry Kranks with some pellets and ask them to chrono it.

It put a pellet straight through one side of those triangular tins of canned ham at 15 yards.

 

Otherwise looks like its a new spring then...?

 

Will a new F1 spring be ok with the original mainspring guide? Or will Ihave to buy one of them delrin top hats and spring guides as well?

 

Why cant I just shove some washers onto the old spring?

 

[im trying to save some freakin pennies. Maybe the new seals just need beddin in?]

Edited December 4, 2012 by ArcticWolf

[toby63 1,236]

I might pop over to a gunsmiths/shop, like Henry Kranks with some pellets and ask them to chrono it.

It put a pellet straight through one side of those triangular tins of canned ham at 15 yards.

 

Otherwise looks like its a new spring.

it shud be doing that at 40yrds let alone 15.

[Acuspell 329]

I might pop over to a gunsmiths/shop, like Henry Kranks with some pellets and ask them to chrono it.

It put a pellet straight through one side of those triangular tins of canned ham at 15 yards.

 

Otherwise looks like its a new spring then...?

 

Will a new F1 spring be ok with the original mainspring guide? Or will Ihave to buy one of them delrin top hats and spring guides as well?

 

Why cant I just shove some washers onto the old spring?

 

[Im trying to save some freakin pennies. Maybe the new seals just need beddin in?]

 

Location: YORKSHIRE.......get away!

 

Whatever you paid for the rifle, with a proper tune it is worth far more than the monetary value. If you don't believe the difference a good tune can make, have a go with a properly tuned one....the £100 or so is money well spent, because you will have a rifle that will still be shooting the wings off midges at 40 yards in 15 years time - and all it will need is a new spring and seals and it will be good for another 15 years after that. Even at £150 for a tune, spread over 15 years that is only £10 a year.

 

I know, you are from Yorkshire, so you can't see the wood for the trees.

[ArcticWolf 7]

 

How much?!

 

All other avenues must be exhausted before I blow the dust off the wallet!!

 

I've been advised that the custom piston seal I bought is a few microns over 25mm, and a small amount taken off with a fine emery paper, should show some increase in power.

 

Although, I have to say, the rifle seems amazingly accurate! I was immeadiately able to hit the centre of a one pence piece, on the home made range!

Seated, at 27 yards!

Speaking as a complete novice, that was pretty rewarding.

Edited December 5, 2012 by ArcticWolf

[ArcticWolf 7]

Just an update if anyone's interested.

I lightly sanded the piston seal with 1200grit emery.

I had a piece of delrin at 1mm thick. [Which I bought to make a tube around the spring, but it was too thick! ]

So I made two washers out of this. One to go on the main spring guide, and the other on the piston end. Put 3 steel washers on the piston end, under the delrin, and one steel washer on the spring guide

Ive had it out this morning, using JSB match 15.89gr pellets.

The results from the chrono app are:

579, 580, 579, 579, 579.

 

So it seems to be bang on 11.8 ft/lb.

 

I also mixed some white lithium grease with ptfe spray and lubed it all with that. I think that made a difference.

Edited December 6, 2012 by ArcticWolf

[pianoman 3,587]

Very consistent return you now have! Best spring piston underlever rifle there is, the HW77 in my view ArcticWolf. Astonishingly accurate whatever calibre. This makes an interesting read to see how you've brought yours up to standard. Sounds like you have a better understanding of what's going on inside your gun than you let on .

 

Well done mate. It's always good to read how a fellow sorts out an issue like this. Hope she give you years of great shooting.

 

Simon

[ArcticWolf 7]

Sounds like you have a better understanding of what's going on inside your gun than you let on .

 

Well done mate. It's always good to read how a fellow sorts out an issue like this. Hope she give you years of great shooting.

 

Simon

 

 

Cheers Simon.

Edited December 9, 2012 by ArcticWolf