FTP900 regulator, chrono usage and anti tamper

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silverbrewer
Posts: 1
Joined: Thu Jul 07, 2016 3:54 pm

FTP900 regulator, chrono usage and anti tamper

Thu Jul 07, 2016 7:54 pm

Hi,
I need an FTP 900 expert and a ballistics boffin who is not wasting time watching either the football, or the tennis!

Looking on here, it seems that a regulator that is working in harmony with the guns settings should be varying about 4 fps, and may or may not have a preference for the lower end or mid portion of the tanks pressure. Is this a reasonable expectation?

Has the regulator in the Ftp900 varied in it's production run? Mine is Serial No. 130883, and it's factory record shows it had a 13 ft/sec variation over 100 shots, which I believe equates to a half inch elevation change at 60 yds. Bit pants! Should I persevere with this regulator and tune it, or replace the regulator and tune with that? If a change, which regulator? New Air arms, or someone else's?

The fps reading on a chrono is the combined result of the air supplied, working on the pellet weight, so how important is shooting weight sorted pellets when comparing chrono readings? My last tin of JSB Exacts had a lightest pellet of .538 grams (8.302 grains, and a heaviest pellet of .556grams (8.580 grains) (I am weighing pellets with a calibrated Oertring R20 balance that should be reliable to .0001 grams (.0015 grains) (.000004 ounce, or 4 millionths of an ounce!!)
I cannot find a calculator that will tell me what difference these two pellets would exit the muzzle at if the regulator had magically given them two perfectly metered slugs of air. (If any variation would happen at all)

Am I allowed to discuss anti tamper plugs on this forum? As an old engineer, (I have been called far worse things on a regular basis) I am well aware of the various removal methods at my disposal, but was just wanting to ask which methods best suit each plug/ headless screw?

Phew!

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Mark112
Posts: 210
Joined: Mon Feb 16, 2015 5:25 pm

Re: FTP900 regulator, chrono usage and anti tamper

Fri Jul 08, 2016 12:05 am

Hi,

...and welcome. This is to be brief as I'm off to bed.

Assuming a 11.5 ft.lb metered slug of air as you put it. an 8.3 grain pellet travels at 790 fps and an 8.58 grain one at 777 fps. There is 13 fps for a start. Spread at 60 yards is about+/- .3". You may have one strike high by .3" and one low by .3". My own experience at these ranges is that the pellet will have a bigger influence on pattern than the rifle.

100 pellets from a tin within 13fps sounds good to me. You may want to try it with weighed pellets.

Goodnight.

Mark
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