Power Curves & the Sweet Spot

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Raj
Posts: 2005
Joined: Sun Feb 15, 2015 9:36 pm
Location: Rugby

Re: Power Curves & the Sweet Spot

Thu Feb 20, 2020 6:54 pm

Mark !!! Must be a few years now since we were all on the old forum. So nice to read your post after all this time.

When I was tinkering on a regular basis (gosh, many folks came to my house with their rifle... lost count), my strategy was to set the power to 11.7 or 11.8 ft.lbs with the hammer spring, then nip it back down to 11.5 / 11.6 ft.lbs with the venturi. I found this method to have many benefits -

Optimum shot count
Flatter power curve (if un-regulated)
Little or no chance of breaking the law
Fewer 'flyers'
“It's the Indian, not the arrow"

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Pete2
Posts: 46
Joined: Sun Nov 11, 2018 9:15 pm

Re: Power Curves & the Sweet Spot

Thu Feb 20, 2020 8:37 pm

Cheers for the replies.

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brk1
Posts: 7
Joined: Mon Feb 04, 2019 10:26 am

Re: Power Curves & the Sweet Spot

Sun Mar 15, 2020 7:11 pm

Great to find these posts, I'm looking to set my S510 up again, probably due to the firing valve deforming a bit, the power was a useable 10.4 -10.9 in the best of the sweet spot with Exacts, about 11.3 with Heavies , then all of a sudden it was down in the high 9's so had definitely lost power, I've had it apart, cleaned up any gook and given the hammer and rails a slight polish and it's gone right back up again, now I just need to set it correctly so reading through this post has really helped, I'm waiting for my Combros to come back after being recalibrated , then I can plug in with the Blueshot cable and record a whole shot string so I know whats going on where.

@Raj, how did you manage to set it up at 11.8 via just the spring then turn down the venturi a bit to make it safe , the hammer spring and valve spring are just set in place, there is no adjustment in them unless you use washers/shims to pack things out. I'm very intersted to learn, I'm fine doing my HW100 as everything is simple to adjust via grub screws/regs/springs etc , I'm now trying to become efdficient with my Air Arms PCP as well, fine with the Air Arms springers, need to learn more about the "S" range of Rifles now. Any help greatly appreciated :)

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Roger5
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Joined: Sat Jul 25, 2015 8:04 am
Location: Hampton middlesex

Re: Power Curves & the Sweet Spot

Mon Mar 16, 2020 2:24 pm

I believe Raj is talking about tha S200 these do have adjustable hammer springs, unfortunately the S400/510 do not, so you are stuck with what A/A gives you, unless you want to play about with different springs. Rog

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brk1
Posts: 7
Joined: Mon Feb 04, 2019 10:26 am

Re: Power Curves & the Sweet Spot

Mon Mar 16, 2020 5:53 pm

Thank you .That would explain things a little clearer :) :) . I did get a message from somebody over on AGF that helped no end, similar to the useful information posted on here :)

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tonyc
Posts: 376
Joined: Mon May 29, 2017 10:55 am

Re: Power Curves & the Sweet Spot

Mon Mar 16, 2020 6:53 pm

brk1 wrote:
Sun Mar 15, 2020 7:11 pm
@Raj, how did you manage to set it up at 11.8 via just the spring then turn down the venturi a bit to make it safe
Rog may know Raj was referring to the S200. I wondered if Raj actually meant the valve spring rather than the hammer spring... it would certainly make sense if referring to the S4xx/5xx series. It's what I would do, except I'd leave the venturi open (i.e. set to give maximum flow through the transfer port) with the spring set to give a slightly lower max, 11.6 with JSB heavies. Raj's method has the advantage of giving the opportunity to tweak it up if the power dropped off a bit.

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brk1
Posts: 7
Joined: Mon Feb 04, 2019 10:26 am

Re: Power Curves & the Sweet Spot

Mon Mar 16, 2020 11:04 pm

Thanks tonyc, that's pretty much exactly the same sdvice I was given this aftrnoon, open up the venturi until max power was found, not overdoing it as it would be just lost space to undo it anymore, then carefully adjust the firing pot to bring the power down to what your recomending, then there's no way in the future it could go illegal with the JSB Heavies.Then let it shoot Exacts at whatever power it comes out at :) :). they certainly shouldn't be higher powered with the Exacts :)

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