AirGunTech: Re Engineering Spring Powered Air Rifles for smoothness, consistency, and to better suit UK power levels.

not updated for a while….does not mean tinkering has not been done and knowledge gained however !!! ;-)

Its been a good few weeks without an update, quite a few PCP projects have been on the bench and I will bring them to the blog when I can…for now however I have something new…more of a challenge.

I reported that Walther were bringing a new springer to the market, the LGV2012, it arrived and while being seriously well engineered rifles the final finish of the gun is not what I personally would pay near £500 for so for now im giving the LGV a miss..however that will not stop me having a go at creating my own.

During the past few weeks a few projects with different rifles have allowed me to explore more of the science of what makes a springer tick, a fellow tuner who frequents a few of the UK forums helped with a HW 55 experiment and initially decided he would have a go at a home brew LGV based on a HW35. He has helped steer my thoughts and answered those questions that sometimes you just can not get your head around…if you see posts by T 20 on any of the airgun forums make sure to read what he has to say….he knows a thing or two about springers 😉

So…back to the new project…It has to be like the new LGV, not a direct copy but like it, so I searched for a base rifle that would take the modifications and could be picked up cheaply second hand.

Bring on the HW80.

Now the specs for the LGV are 25mm piston, 88mm stroke, piston runs in a sleeve but has a skirt that is larger (diameter) and runs on bearings…bit like the AirArms TX200 piston. The cocking lever slides on a sprung bearing and the piston rotates…

Can I do all this with a HW80?

Now venom /V-mach offered a sleeved conversion for the HW80, I know of it but have never seen one so what I will show is my take…. how I would do it. My plan is to have a rotating piston, utilise the new cocking shoe HW have just phased in but add bearings to keep its operation smooth. The stroke will be set to around 80mm, this will give a swept volume of 39CC…this gun will be re engineered for UK sub 12FPE use only.

During the tune work on a HW55 I was able to experiment with stroke and swept volume as well as transfer port tuning, there looks to be a magic static compression ratio that must not be ignored, set below it and the firing cycle can get slammy with light weight pellets, set way below it and the gun will suffer from a smashed piston. I will explain more as the build unfolds…It also probably deserves a thorough write up also as there is quite a lot involved.

There is one ironic part of the build, the piston I have chosen to use is the actual Walther LGV piston, its ordered and hopefully will be with me in a few days, i can then decide what machining is needed to get the 80mm stroke and convert the piston to run a Vortek vac25 seal. Of course it may not even lend itself to the build yet…im hopeful it will obviously. The one hurdle i do have some concerns about is the trigger sear engagement on the piston, the LGV piston is very different to the HW piston so there may be some alterations needed.

The gun is already to hand, its an early .22 80 that was bought for £120, its been painted, it has a chopped .22 barrel but it has a nice Mk1 right hand HW80 stock and its transfer port is untouched. The barrel will be swapped for a 410mm .177 barrel (which is ordered) the original barrel will be cleaned up and re blued and kept with the rifle to keep its history. A barrel weight will be added, 20mm OD around 180 to 200mm long, this will be blued steel. The plan for the stock is to refinish it, stain it back to walnut BUT stipple the pistol grip and belly of the for end then blacken them much like the HW98.

The piston sleeve is also to hand, 30mm OD 2.5mm wall (BS3602Part1 CF5360 NBK) CDS tube, it slides into the action beautifully and its machined accurately on the ID and looks to be perfect for the VAC25 seal I want to use.

The next update for this build will have the new barrel and I hope the piston and cocking shoe all to hand..the build will then officially commence.

 

More soon 😉

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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