Help please

[Hairybiker59]

I acquired a second hand .177 air arms s410 the other day and today I decided to do some indoor shooting.the distance I was shooting was 13 yards.i filled to 190 bar and was getting almost pellet on pellet unti all of a sudden the pellet started to drop lower and this was only after 30-40 shots.i put the rifle on the bottle and it was reading 130 bar.i chrono'd at the 190 fill and the rifle was doing 11.3 but at 130 bar it was reading 10.4ftlbs.anyone tell me what the hell is going on

[Hairybiker59]

Have just done a 20 shot string chrono test,stopped at 20 has you can see from the test the power is going down so I stopped.
Un-weighed h@n ftt
Filled to 190 and after 20 shots was down to 140 bar
775 fps
772
770
771
771
766
766
762
763
762
760
757
752
754
747
742
739
736
736

11.22ftlbs
10.71
10.11

775fps
756
736

If I'm correct in working out the fps from highest to lowest then that's a 39fps vary over only 20 shots and would have got worse had I gone on

[wezdavo]

That's a strange set of figures.. Are you reading the pressures from the gun or the bottle? How old is the rifle and did you buy it new? Is the chrono reliable?

[Hairybiker59]

That's a strange set of figures.. Are you reading the pressures from the gun or the bottle? How old is the rifle and did you buy it new? Is the chrono reliable?

It's a new combro with a new set of batteries,I read from the pump and bottle

[Hairybiker59]

That's a strange set of figures.. Are you reading the pressures from the gun or the bottle? How old is the rifle and did you buy it new? Is the chrono reliable?

It's a new combro with a new set of batteries,I read from the pump and bottle

Forgot to add that the rifle is 2010 and bought second hand a few days ago

[wezdavo]

Sorry mate, just re-read your post... So the fill pressures are from the bottle and I guess the poi drop corresponds to the chrono readings..

I would take it apart, check the hammer rail for debri or corrosion, check the firing pot measurement and if it were 57-58 mm and it is behaving like this there is a problem mechanically.

In this case I would re-spring the exhaust + hammer valve and fit a new firing valve..

[wezdavo]

2010.... Anti tamper! is it still in place or has it been removed?

[wezdavo]

If it has been apart before it would suggest someone has being playing with it and set the firing valve up wrong.. So hopfully in this case you may not need to buy any parts, just set it up to standard specs...

[Hairybiker59]

Sorry mate, just re-read your post... So the fill pressures are from the bottle and I guess the poi drop corresponds to the chrono readings..

I would take it apart, check the hammer rail for debri or corrosion, check the firing pot measurement and if it were 57-58 mm and it is behaving like this there is a problem mechanically.

In this case I would re-spring the exhaust + hammer valve and fit a new firing valve..

The anti tamper has been removed wether it be via the last owner or not I don't know,he did say to me that he had fitted a new hammer spring but gave no reason has to why,he also said while the rifle was apart he polished the hammer rail and hammer.i shall strip it and have a look at the firing pot measurements

[Mark112]

Hi,

My guess is that the previous owner has fitted a stronger hammer spring off t'internet in order to up the power somewhat and it's now using a lot of air per shot. Put an original spring back in and adjust the power with a pellet like JSB/Daystate heavies and you should be well within the legal limit for other pellets. Check that the firing pot is set correctly (57mm IIRC) while you are there. For reference my own S410 in .177 returns 60 'sweet spot' shots within a spread of 12fps from a 145 bar fill and 85 shots within 20fps from a 158 bar fill.

Mark