S400 advice needed

[chris.e]

Could anyone give me a few pointers on how to improve the consistency of my s400.

It's a .177 classic and the last time I used it was about 2yrs ago and it was shooting fine and if memory serves me right, had a less than 20fps spread from 170bar down to 110bar doing 11.4 ft/lbs.
I've decided to use it again but before using it I decided to put it through the chrono just to see if everything was as it was when I last used it.
Filled it to 175bar and went down to 120bar. Through the shot string the power crept up to near Fac level and had a spread of 40+fps.
So, I partially stripped it down and cleaned the hammer and rail and I've turned the power down to just under 11 ft/lbs but the spread is still 40fps.

The thing is, about 12mths before I last used it I changed all the seals and replaced the valve spring so now I'm wondering why its like it is.
I was thinking of changing all the seals again while its stripped and this time replacing the hammer spring to see if that improves things.

Any pointers, lads?

Cheers.

[Blackbaronfish]

Where did you get the hammer spring from

BBF

[Mark112]

Hi,

Did you change the valve itself (about £8 IIRC from Julian Bond on this site)? I had a very arched curve on my .22 S410 and fitting a new valve really flattened it out. I posted detailed notes together with lovely graphs (mmmmm!!) on the older version of this site under 'sweet spot' hopefully one day it may return?! A chap called cloverleaf posted this:- http://www.airgunforum.co.uk/forums/sho ... +extrusion on another forum explaining all.

Mark

[chris.e]

Haven't bought a hammer spring yet, it was the valve spring I previously bought off Julian.

I've just read Cloverleaf's Post on exhaust valve issues (cheers Mark). No, I didn't replace the valve but it seems the white nylon head type found in earlier models are less prone to problems.
From memory I'm pretty sure mine is a white nylon one but that said, I'll take a close look at it and replace it if needed.
Its looking like a full set of seals, both springs and possibly a new valve and then see how I get on.

Cheers for that, very helpful.

Atb

[sparrowhawkfalconer]

Hi how easy hard is it to get to the valve to check this, im a noob when it comes to this, thanks

[chris.e]

Very easy IF your 400 has no anti-tamper fitted. (see YouTube)

All you need is a set of Allen keys but make sure you empty the cylinder of ALL it air first by dry-firing until it dumps all its air at around 40 bar.
Take your time and make sure you know which seal went where when refitting. (You can take photo's step by step to help you in reassembly.)
And when refilling with air, make sure to cock the rifle first and leave it cocked until you've reached your required fill pressure. If you don't, it won't fill.

Atb