Strange S400 Chrony results left me baffled

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Snesy
Posts: 5
Joined: Mon Aug 27, 2018 6:52 pm

Re: Strange S400 Chrony results left me baffled

Sat Sep 08, 2018 8:25 am

A little lost in translation here I think lol

The shot string I was referring to was done before I noticed the leak from the power adjust grub screw, another test after fixing the leak has brought the results back up to around what you mentioned 👍

Also adjusting the screw did adjust the power to, I was referring to the leak.... no matter if I wound it fully in or out it would still leak, the power still adjusted accordingly.

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TenMetrePeter
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Joined: Wed Jun 29, 2016 5:40 pm
Location: Luton Beds UK

Re: Strange S400 Chrony results left me baffled

Sat Sep 08, 2018 12:46 pm

Understood!
S400 MPR Precision with TMP alloy stock.

https://www.youtube.com/channel/UCaCf9G ... A-mGhZQlGw

“Why do we have noses that run and feet that smell? “

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TenMetrePeter
Posts: 859
Joined: Wed Jun 29, 2016 5:40 pm
Location: Luton Beds UK

Re: Strange S400 Chrony results left me baffled

Sat Sep 08, 2018 12:53 pm

S400 MPR Precision with TMP alloy stock.

https://www.youtube.com/channel/UCaCf9G ... A-mGhZQlGw

“Why do we have noses that run and feet that smell? “

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rob2hook
Posts: 14
Joined: Sat Jul 21, 2018 10:29 am

Re: Strange S400 Chrony results left me baffled

Sun Oct 14, 2018 9:38 am

It sounds like you have this sorted now, but I was thinking that the other variable you could have measured with the shot string is the cylinder pressure. I was surprised (gratified) when testing my S400 that the pressure drop is almost linear, indicating a good balance of valve spring , hammer spring/weight and suggesting everything is clean enough to be moving as it should.

I'm sure some folk have already used such data as an analytical tool, but I'm still thinking it out and don't really want to have to encounter all the potential problems to document their effects on the power and consumption curves! My initial thoughts on the almost linear power curve but rising velocity was that the valve had deformed into the seat and so restricted the flow at higher cylinder pressures. This possibility would have been borne out by lower than average pressure drop per shot at the high pressure end.

Rob.

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TenMetrePeter
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Joined: Wed Jun 29, 2016 5:40 pm
Location: Luton Beds UK

Re: Strange S400 Chrony results left me baffled

Sun Oct 14, 2018 10:51 am

I doubt if that standard AA gauge in the rifle would show any shot to shot pressure difference. Mine will not show in 1 bar increments which is what you would need. Maybe every 10 shots sampling might be readable. How did you do it?
S400 MPR Precision with TMP alloy stock.

https://www.youtube.com/channel/UCaCf9G ... A-mGhZQlGw

“Why do we have noses that run and feet that smell? “

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rob2hook
Posts: 14
Joined: Sat Jul 21, 2018 10:29 am

Re: Strange S400 Chrony results left me baffled

Sun Oct 14, 2018 5:31 pm

I left the charging hose attached so as to read from the more accurate gauge and took readings every ten shots. The resultant curve was as close to linear as you could expect with the accuracy of interpolating the gauge's readings.

Rob.

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