Power Levels

[martini1215]

I would like to ask for the benefit of the knowedge on the forum please.
I am fairly new to Theoben PCP rifles and recently gained a Rapid in .177 flavour.When itcame to me it wasn't holding air at all and it ended up not just being one leak but a number of them ganging up on me.
I have completely resealed it and stripped/rebuilt the reg and now there are no leaks at all.
I have put it over my FX Chrono and got steady results 8.8,8.8,8.8,8.9,8.8,8.8,8.8,8.7,8.8 Ft/lb could anyone give an idea of whether this is a decent level for these guns or can I get it to go a bit higher.
This is with 8.18 grain pellets and I dont want to risk going over the legal limit if a different pellet were to be used.
I aren't sure whether to try and tweak the reg or to head for the hammer although I believe that is now behind an anti tamper cover which I would have to defeat before going ahead.
Many thanks for any opinions given

[Ca_Varminter]

From a Yank from across the Pond
It seems a bit low...
With a Reg.. I would expect 11.5 fpe..

So not knowing the internals... hammer-spring length and preload..
Also the set pressure of the Reg.
I would Guess it may need a bump up in the reg pressure...

But I would wait for KevG to jump in!!!

Good Luck,
Stuart

[martini1215]

Thanks Stuart, wow that was quick replying, are you guys just getting up? We sat watching evening tv listening to the rain on the windows lol.
I will admit I have no idea on pressure setting of the reg, I used a Mk1 eyeball and photos to estimate the same positions to nip the nylock nut down to. I knew O rings internally on the reg were shot a one of the leaks was a steady whistle from the bottle coupling bleed hole.
The O rings in there were hardened and brittle to the extreme of being impossible to remove whole, they just broke out.
I do have a feeling someone else has been in there tinkering unsuccessfully then binned the project on some unsuspecting me.
There was no barrel screw in the hole, two O rings on the exhast valve stem, barrel was rotated so that the transfer port was only half lined up. Grease there was less on the Fonzs haircut.
Anyhow I feel I have got somewhere as it holds air and shoots now, so just to up the power a little maybe.

[Millingman]

Get the barrel transfer port lined up properly, I've got two ports on my barrel setup for different powered levels, by twisting barrel round 45degrees I can reduce power for plinking in the garden etc. Using two o rings on the valve stem is not a great idea, just use one, less friction, use a very small amount of silicon grease or silicon oil mollykote 33 grease on the stem for lube. Don't over do it. To fine tune your hammer spring you really need to get rid of the anti tamper from the hammer adjuster screw at the back of the block. Kevg can talk you through it, he's helpful. A reg tester would be a good idea to check your pressure isn't to low.

[martini1215]

Thanks millingman, I read various tutorials on strip and rebuild of the gun and all said just one O ring on the exhast stem so I rebuilt it with just the one, the position of the second groove didnt seem to point to it being a lot of use either.
I had a hell of a job degreasing the block on this before rebuild too, it was grey like lithium grease and enough on it to fry a breakfast, anywyway I was guessing this may have contributed to O rings perishing as none of them were much good.

[Ca_Varminter]

.....I read various tutorials on strip and rebuild of the gun and all said just one O ring on the exhast stem so I rebuilt it with just the one, the position of the second groove didnt seem to point to it being a lot of use either.
I had a hell of a job degreasing the block on this before rebuild too, it was grey like lithium grease and enough on it to fry a breakfast, anywyway I was guessing this may have contributed to O rings perishing as none of them were much good.

Yes only one O-ring is installed on the Valve-stem.
Install it in the groove towards the hammer side.
That 2nd groove is actually a pressure interference groove.
High Pressure Air enters this groove. The turbulence created, slows down the velocity of the air.
So there is less stress on that little O-ring!

The Original Rapid, the Bolt Body was covered in the silvery grey molybdenum grease!!
That was always the first thing I cleaned of my New Rapid!!

Good Luck,
Stuart

[KevG]

you need to get the reg set to the proper pressure first, this is your foundation to tune the gun to, other wise you just end up chasing  your own back side and a badly tuned gun.correct pressure for sub 12ftlbs is 1500 psi
kevG

[martini1215]

Ok Kev .
Many thanks for that, its surprising the combined knowledge of the internet.
For a simple gun these are a lovely piece of engineering, hours of fun without even entering the realms of shooting them.