Spring Gun Tuning

[rehmk5]

Hi Paul,

Thanks much for your reply. Non-hold sensitive R1 at 10.5 ft/lbs M.E.? Very interesting. And with the factory weight (heavy) piston at that! Imagine!

I had a custom, lightweight piston made for my .177 FWB124 springer (factory piston: 10.5 oz & custom 124 piston: 8.5 oz), and put in a soft tune kit that had 7.9 gr JSB Exact Express 4.52 doing 770 fps (7.9 gr CPLites did 730 fps with same tune due to tighter fit). Hold sensitivity was reduced, but still had about 1" vertical difference between where the groups hit at 40 yds, sitting w/rest vs. standint w/rest.

Do you remember how the R1/hw80 was at 12 ft/lbs ME? I'm not sure I have anything to drop my R1 down to 10.5 ft/lbs, but I do have an old Jim Maccari 13 ft/lb kit I might be able to use to get down to an even 12 or 11 via no spacing.

Again, thanks for your comments.

Robert Hamilton

[Paul Hudson]

Hi Robert.

At a shade under 12fpe it was tooth-jarring

I dropped the power simply by shortening the spring slightly. I also sized the seal for a sliding fit - that is, the piston and seal would slide gently down the cylinder under its own weight, stopping if the transfer port was blocked.

Darren - I fitted it in a Sono Kembang GinB stock which added nicely to the weight.

However, one of my 97Ks sat in a brute of a walnut stock that I added around 5lbs of lead to - and you couldn't tell unless you tried to lift it . The simplest way was to fill a few lengths of 15mm copper water pipe with lead, drill a series of 15mm holes into the end of the stock under the butt pad, then slide the weighted pipes into place.

Paul.

[rehmk5]

Teeth jarring at 12 ft/lbs? Well at about 17 ft/lbs, my R1 has a fast bit of kick. But with it moving groups vertically with differences in hold style, my R1 has been a closet queen.

Thanks for the detune tips.

I've been happy using my TX200's for small pest hunting at local farms/ranches. Got 54 California ground squirrels recently at a local cattle ranch. Rancher was going to poison them out (slow death by internal bleeding...takes 2/3 days to die sometimes), so I did my best to thin his pest population down to the point he doesn't go the poisoning route.

Robert Hamilton
Calif, USA

[Paul Hudson]

Teeth jarring at 12 ft/lbs? Well at about 17 ft/lbs, my R1 has a fast bit of kick.

I found the HW80 to be a bit of an enigma

At 17 to 18fpe they're sweet and smooth; at 12fpe they're "tolerable" but unpleasant. At 10.5fpe they become sweet and smooth again, and a genuine pleasure to use. With the lighter, 7.9g pellets, I was getting the same muzzle velocity as with 8.4g pellets at the higher power, so the trajectory and POI was exactly the same.

Have fun with your tinkering

Paul.

[rehmk5]

Well, thanks for sharing your HW80 experiences Paul.
Much appreciated.
Few in the USA have experience with the lower power levels.
Robert Hamilton, Calif, USA
(now back to reading the news about our idiot politicians)

[Paul Hudson]

(now back to reading the news about our idiot politicians)

Nothing different on your side of the pond then either...

Let us know how you get on with the 80.

All the best,

Paul.

[electric sheep]

Just squeezed mine up to 23fpe and it's fantastic, a real self contained FAC air gun with enough power to be worthwhile. Over 900 fps with light pellets and 800fps with 16g.

[Hsing-ee]

If you want to replace a leather washer with a high-quality plastic one, then Jim Maccari sells some which might fit your rifle and they are inexpensive.


http://www.airguns.citymax.com/page/page/251485.htm


Alternatively, T.R.Robb makes PTFE ones which may or may not be an improvement on the original.

http://www.trobb.f9.co.uk/

[chrisarvor]

hi
I havent stipped an airgun down since i used to do my Diana model 16 which was just after the ice age!!!!!
I bought a Boxer spring and new piston seal and breach washer and the washer behind the piston for my old BSA Mercury mk2
I actualy thought they has sent me the wrong piston washer as it wasnt leather!!!!!!!
so i stipped it down and put some wet an dry paper 1000 grade on a broom stick and sprayed WD40 in there and gently cleaned out the air chamber.
When i put i back together i nicked the O ring for the piston so i looked in my o ring box and found a near as dam it one and put it all back together but first washing out the air chamber with some WD 40 . And putting some down the barrel.
Eventualy got the bugger back together without any spring compresser and its superb.Quite a super little gun.
Now i dont understand why your all saying dont use this or clean with that if it works the old fashion way why change it????

[Hsing-ee]

Now i dont understand why your all saying dont use this or clean with that if it works the old fashion way why change it????

Because if you use WD40 to lubricate your BSA Mercury it will diesel like a farting elephant, ruin the spring and give inconsistent power and accuracy and have a short life. WD40 isn't a lubricating oil, it is a very volatile penetrating solvent for freeing rusted components and for dispersing water. After it has finished exploding in your compression tube, it will evaporate off and your gun will be running dry. You will need a new seal and a spring in only a few months.

Lots of people have used the Tuning Guide to make their guns better. Also, it is a tune that has been in use for the last 29 years so I think that it counts as 'the old fashioned way' at least as much as scrubbing with abrasive paper and WD40.

If you follow the instructions you will have a nice, smooth accurate rifle that will last a long time and will be a pleasure to shoot. Lubing with WD40 and changing the spring and seal will give a workable gun, but it won't give anywhere near the best performance it is capable of. If you HAD followed the guide then you would have smoothed out the cocking slot and you would not have knicked your seal.

Read it and try the guide, you might be pleasantly suprised!

[Marzy]

Just like to say that I read through lots of tips from this site before attempting to strip down and rebuild my Webley Mk3 (many thanks to all who contributed). the gun had been dry stored under the stairs since the late 1970s with just the odd wipe down and pellet through it every few years but, was seriously underpowered and all the grease had solidified.

I stripped down every moving part, gave the barrel a good pull through and light lube, degreased and cleaned everything before applying new grease and lube, fitted a new spring and PTFE seal which took a little wate with all the wet and dry rubbing but, now moves up and down the cylinder with gentle but firm finger pressure and sounds like a bicycle pump. Put motorcycle chain lube on the new spring to dampen it down while I sealed the loading port barrel with MB grease and ensured a thin smear of gasket sealant went around the edge of the cover plate. With the loading port in the "load" position, working the underlever cocking arm back to the point where it almost engages the trigger, and then letting it go back again will result in a pleasant Pssst once the loading port is flipped back to the firing position, indicatin a good seal.

All in all the gun is now rejuvenated, much more powerful and smooth and was instantly shooting around 2" higher than the scope had previously been set for at 25 yards although it has taken around 100 pellets to start grouping decently as it was obviously bedding in.