Hw80

[thursodog 353]

Hi folks.

This is the final chapter on my fac that I have stripped several times and done lots of work to in a steep learning curve of more indepth tuning over the last 3 years.

Here's something that might interest some of the tuners out there.

I've stripped and cleaned out 3 separate cylinders and found each one to have exactly the same differences with internal bore diameters.

We are talking between hundredths and thousandths of an inch which is enough to make exact fitting delrin buttons fitted to the piston run slightly inconsistently

Before I started resizing the bore I could not get the buttoned piston into the cylinder without undersizing the buttons which makes the work futile

The cylinders are 2 from the nineties and one from around 2002

Starting at the thread end there is the smallest diameter starting from the cylinder thread for about 30mm along gradually increasing to the largest diameter in the cylinder right along to the end of the cocking slot nearest the transfer port which was slightly oval.

Then the bore diameter reduces slightly from the cocking slot to the transfer port to between the diameters previously mentioned.

This last diameter runs consistently from the cocking slot to the transfer port.

I lastly found that if I wrapped my hand around the tube along the length of the cocking slot I could compress this section and alleviate the oval shape and attain the exact same diameter as the transfer port end.

So without further ado I got some jubilee clips in place along the oval section (in for a penny!!) and tightened up until I had reduced the diameter a little more than was required.

Hey presto the cocking slot section and transfer port end of the tube had come to the exact diameter with no oval once I had removed the clips ( this took 3 attempts at gradually decreasing the bore diameter along the cocking slot section.

I'm using an internal bore gauge that can be bought from any good engineering shop.

This now left the last section of about 30mm at the thread end which was way smaller in diameter.

So after 3 hours of very careful honing with a homemade hone, emery cloth, steel wool and a battery drill I at last had the entire cylinder the exact same diameter from one end to the other.

Haven't done the other 2 yet but will.

I next glued in 4 - 5mm buttons at the seal end of the piston and 5 - 5mm buttons at the other end and simply turned them down to fit snugly inside the cylinder.

Well chuffed with how smooth the piston now ran within the cylinder and with not even the slightest rattle or tight part.

I then sized my V- Mach piston seal, cleaned everything and stuck my fac back together and hoped for the best.

This has taken 6 hours to do today and I'm in the middle of an acute attack of gout and can hardly walk but will not stop till I get this done.

This gun has a new short K barrel threaded with a mod on the end and on my ticket.

I cocked the rifle and felt the hair stand on the back of my neck!

Silky silky F*cking smooth to say the least and sounded brilliant.

I've buttoned quite a few Weihrauchs now but nothing is coming close to this beauty!

I fired the rifle into a giant log 15 yrds away to simply feel the recoil and look at the muzzle for flip.

19 fpe gave a smooth bump to my shoulder that was not excessive and rather brilliantly no sign of any muzzle flip.

It is uncanny how smooth and manageable it shoots for the power its putting out on H&N FTT 14.66 grn at roughly 760 fps

So next thing is the chrony and straight away its shooting like a bedded in gun and only showing a difference of 9 fps over a 10 shot string which I'm thinking is bloody brilliant, I'm having the best tuning day in 3 years of hard graft and quite a few F*ck ups and triumphs.

Lastly just as the swelling in my right knee and left ankle is getting to the point that I think I'm ready for the knackers yard I set up a target at 30 yards and proceed to shoot single hole groups as good as my .177 V-glide 97 does.

I'm in agony now with a massive smile on my puss and nothing will wipe it off for the foreseeable future.

Me and this old have had a few ups and downs over the last 3 years and its now safe to say I put her in the cabinet tonight after a clean and oil thinking all there's left is to enjoy shooting a superb springer that I still can't believe shoots so smooth and accurate at nearly 20 fpe.

Last job will be to bed in and write down my poi at ranges from zero to 60 yards, then its more happy hunting and less tuning, well maybe less tuning?!?

 

Chris

 

 

[Coypu Hunter 486]

That's dedication for you... Well done, mate -- a great result after all your hard work.

 

Now stop fiddling with the bleedy thing and go and shoot it, you saddo!

Edited August 4, 2014 by Coypu Hunter

[thursodog 353]

How very true

Saying that it takes a geek to know a geek

 

Cheers

 

Chris

[Coypu Hunter 486]

Yup, I've spent too much time recently inside my 97K rather than shooting it, and a V-Mach kit will arrive next week...

 

Mind you, it's still knocking down magpies despite having to replace the spring, so I'm reasonably happy, and still shooting!

 

Don't know if I'd have the patience to do what you've done, a V-Mach kit will do for me.

Edited August 4, 2014 by Coypu Hunter

[thursodog 353]

The V-mach kit helps a good bit in the 97.

You will need to size the seal though.

 

Cheers

 

Chris

[Coypu Hunter 486]

The V-mach kit helps a good bit in the 97.

You will need to size the seal though.

 

Cheers

 

Chris

 

Do they make them a little oversize or something, to allow for variations in the size of the compression chamber?

[thursodog 353]

No they come with washers to adjust the power.

My .22 hasn't any washers and is shooting 11 fpe.

Lovely and smooth.

My .177 97 has a V-glide fitted and is superbly accurate and smooth to shoot

[Coypu Hunter 486]

No they come with washers to adjust the power.

My .22 hasn't any washers and is shooting 11 fpe.

Lovely and smooth.

My .177 97 has a V-glide fitted and is superbly accurate and smooth to shoot

 

I was talking about the need to size the piston seal that you mentioned, rather than managing the power output. Is the piston seal normally a bit over-sized to accommodate any variations in the piston chamber's internal diameter?

[thursodog 353]

I'd hazard a guess at yes its made big to perhaps accommodate the difference in cylinder diameters.

I fit mines onto the piston then tape the scraper ring onto the piston to stop the seal revolving then stick it in the lathe and apply gentle pressure on the sides of the seal with fine wet and dry.

Doesn't take much, just a bit of trial and error.

Save up for a V-glide they are things of beauty and brilliant performers.

My .177 will piss over pcp's any day.

For a springer its really easy to shoot apart from weighing nearly a stone scoped which doesnay put a solid built Scots loon like myself off :gunsmilie:

[j j m 6,626]

good write up bud

[thursodog 353]

Cheers mate

[moxy 617]

Cracking read that chris

 

Your certainly dedicated. Nice one

[thursodog 353]

Cheers Moxy.

It gets quite addictive at times.

 

Atb

 

 

Chris

[Rez 4,961]

Might be a bit late here but my v-Mach kit and 97kt install went without a hitch apart from the pivot pin being a bitch, no resizing or nothing. Same with my 98 and both are now my only field and hft buddies. PCP...?! Pahahahahha. V-Mach system any day.

[Coypu Hunter 486]

Might be a bit late here but my v-Mach kit and 97kt install went without a hitch apart from the pivot pin being a bitch, no resizing or nothing. Same with my 98 and both are now my only field and hft buddies. PCP...?! Pahahahahha. V-Mach system any day.

 

I'll see if it fits well when it gets here later this week. The tighter the better, as the Bishop said...

 

The pivot pin, like the trigger unit pins, is tapered, which might explain the problem. I stick a thin screwdriver through the holes to align them, then push the screwdriver out with the pin itself.