S400 "alternative" firing pot setting

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Stoohundred
Posts: 122
Joined: Mon Oct 19, 2015 9:48 am

S400 "alternative" firing pot setting

Thu Nov 26, 2015 7:47 pm

Hi, when I had my s510 a few years ago I set it up with the Venturi screw wound all the way out and reduced the power by screwing the firing pot in a little.

Admittedly this was a pain in the A to set up as I had to strip it about 4 times to get the power to the correct level but I found that it made the rifle more consistent over a full shot string and also meant that in theory the rifle could never go over power without stripping the gun.

Am now thinking of doing the same with my MPR , but am just wandering if anyone here would know where abouts to set the firing pot at, just to save me having to strip it down so many times.

I know the standard setting is about 57.5mn but was gonna start with 55mm and see what I get, but if anyone knows for sure what setting would get me 780fps then please let me know. (Wish I had made a note of it when I did the 510 now)
Many thanks , Sean
AA MPR FT .177 8-40x60 Tasco Custom Shop (FT Setup)
S200 MK2 .177 Robert Lane Reg Hawke Airmax 3-12x50 SF FOR SALE

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32:1
Posts: 84
Joined: Sun Jul 26, 2015 6:08 pm

Re: S400 "alternative" firing pot setting

Sun Nov 29, 2015 7:48 am

I have done the same to my 510
I had pot set at 53mm with a 40g hammer
If it aint broke, fix it till it is

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Stoohundred
Posts: 122
Joined: Mon Oct 19, 2015 9:48 am

Re: S400 "alternative" firing pot setting

Sun Nov 29, 2015 12:25 pm

Thanks for the reply, is 40g the standard hammer weight or have you modified it?
AA MPR FT .177 8-40x60 Tasco Custom Shop (FT Setup)
S200 MK2 .177 Robert Lane Reg Hawke Airmax 3-12x50 SF FOR SALE

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32:1
Posts: 84
Joined: Sun Jul 26, 2015 6:08 pm

Re: S400 "alternative" firing pot setting

Sun Nov 29, 2015 12:45 pm

The original hammers are 45g
I turned it down and down and down to see what weight worked best with my settings and 40g was bang on, then bought another from Julian, the lighter one I kept for a planned diy reg attempt
If it aint broke, fix it till it is

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Stoohundred
Posts: 122
Joined: Mon Oct 19, 2015 9:48 am

Re: S400 "alternative" firing pot setting

Sun Nov 29, 2015 2:23 pm

Thanks for the info, what sort of difference did it make?

Did it flatten the power curve or have a significant effect on the FPS spread?

Would love to see any chrono strings/graphs if you have any.

I have just put mine back together set at 55mm but still need to use the Venturi screw to tune it down.
I really need to get my new scope set up so am gonna just leave it at that for the moment but will probably change it next time I have it apart.

What sort of power level do you get @53mm with the standard 45g hammer? Would that be over 12ft lbs?

Just thinkin that if I wanted to leave the hammer as it is, to achieve 11.3ft lbs /780 FPS then may need to go down to 50-52mm ?
AA MPR FT .177 8-40x60 Tasco Custom Shop (FT Setup)
S200 MK2 .177 Robert Lane Reg Hawke Airmax 3-12x50 SF FOR SALE

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32:1
Posts: 84
Joined: Sun Jul 26, 2015 6:08 pm

Re: S400 "alternative" firing pot setting

Sun Nov 29, 2015 3:41 pm

I removed adjuster as I thought Id make the other parts work better, Im no expert and someone might chip in with their findings, but I found less pot lenth helped lower power, make more shots and better consistancy. But chasing things I went past these and found things soon get messy :lol:

Its a balancing act and the smallest thing changes things, somtimes drastically

I then chose to fit a lane reg, this took a bit of fine tuning but it seemed easier as the air pressure is consistant so your settings are more focused, that said Im still tweaking to find the impossible :lol:

The reg thing has got better as Im just fitting another to my .22 and now exploring hammer travel not just weight/speed
If it aint broke, fix it till it is

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Pete2
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Joined: Sun Nov 11, 2018 9:15 pm

Re: S400 "alternative" firing pot setting

Sun Jan 29, 2023 6:36 pm

Resurrection of an old topic.

I have removed the reg from my 500, set the pot to 57mm but with a 37gr hammer. Running to high, got to reduce pot length. Going to try 56 with 37.
37 worked really well with the reg though

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