My HW35 tune

[bigtoe]

Hi guys, first post on this forum so please be gentle

 

I have owned my HW35 since I was 14, im 35 now and it has gone thru a few rebuilds along its life but always to near stock spec. I decided recently to try to get back into airgunning as im just starting to get over ME (chronic fatigue syndrome) which I have had for well over 2 yrs. With the extra energy I have I thought of no better way than spending it outdoors shooting, I used to have 270acres to shoot on but thats long gone so for now im looking for a new shoot but have lots of time for rifle tuning.

The rifle had been fitted with what looks to be an Ox mainspring and the old leather piston had been replaced with the new type piston unit....it shot awefully!!

 

I had forgotten what it was actually like to shoot and with me not being anywhere near as fit as I used to be I decided some action was needed.

 

First I managed to find a very nice custom built walnut stock, I will post pics later and I must say im thrilled to have found it, this alone greatly changed how the rifle handled and shot.

 

Second I managed to pick up a chronoscope up off ebay..I paid quite a bit for it although less than the £90+ wanted for units that are still available..this I have found the most useful tool I have ever bought.Staying legal while tuning is VERY important.

 

Next up I had my already shortened .22 barrel shortened again..After talking with many friends and keen airgunners it seemed all I really needed was 12inches to retain good accuracy and power upto 35m or so.I know there are shortfalls by shortening barrels this short also but with me tuning and replacing many items within the gun I gave it a go.I must say im glad I did as testing upto 20m has shown no loss of accuracy upto now and im sure longer range testing will prove just the same.

I also had the barrel threaded 12"UNF to except a Parker Hale silencer.

 

Turning to the inside of the gun I have started on a bit of a journey, at the moment im using the standard piston unit with a PTFE washer but I have decided to make a new piston unit along the lines of a lazerglide unit. As I gather more details of what I will make I will post them and post drawings also if needed.

Next came the spring. Many say square section springs are not the way to go so I bought a quality round aftermarket one that is to original specs...thing is I haven't used it. I decided to cut the square section spring down a little and resquare up the end..in all I cut 6 coils off with the re-squareing reducing it to around 7 coils shorter.The reason for doing this was that upon removal 2 1/2" of the spring had become deformed thru over compression and was obviously doing next to nothing.

I replaced the ageing spring guide with a newer unit (which I will also replace with a custom unit later) and proceeded to relube the gun and test it.

 

Well with a spring 2 1/2 " shorter you would think I had a huge reduction in power..not so!! I was still seeing close to 10Ft/lbs and I could now cock the rifle with the silencer fitted using 1 finger to pull on the barrel easily.The spring was hardly under any compression when uncocked and the internal noise had dramatically reduced.

10 ft/lbs is not enough though...11.75 is my target or a little higher so now came the time for piston weights etc. Im having weights machined up by a friend but for now im using washers which has allowed me to experiment a little to get the power up to where I need it to be.I have added around 1/2" of washers to the nose of the piston, these only just slide down the piston and do not rattle etc when firing, I also greased them a little.This brought the power up to around 11ft/lbs with only a VERY slight increase in cocking effort needed.

I proceeded to pump out 200 rounds or so to get the internals settled before I took an average power reading...11.1ft/lbs with RWS Super H points.As you see im getting close to where I want to be but still no cigar.So, a quick strip down and a washer added to push the spring forward off the spring guide by 1/8th" and im now running at 11.6ft/lbs.cocking effort again went up but its nowhere near what it used to be.Internal noise is still very low and recoil is around 1/3rd what it was or less....the rifle is now a pleasure to shoot.

 

One last mod I have performed is to open up the retaining cap hole on the Parker Hale silencer and tap it 1/2" UNF to except an old ally silencer I had lying around.while this makes the barrel 22" in length it has made it VERY quiet also for back garden plinking etc.I have a spare PH end cap for hunting trips etc to just use 1 silencer.

 

I will post pics and update this thread if your interested..im keen to try the other mainspring and to see how much I can remove off it etc when I have the new piston and custom spring guide made.For now im sure as the action settles I will probably see 11.7+ft/lbs for my current state of tune as the new washer beds in a little.

[red_stag88]

I'm very sorry to here of your ME.

 

Sounds like you've got a good weapon there!