Air Arms Owners Club

John814ce wrote: ↑

Mon Mar 18, 2019 6:15 pm

I think the answer to us as sub 12ftlbs air gunners is when you buy a new or second hand unregulated aa rifle and you think that say a .177 running at 780fps from new at 160bar ish is going to be over power then tell the gun smith about your concerns and he/she will lower the power to stay well within the laws.

What’s a gunsmith?

A gunsmith is a person who repairs, modifies, or designs, or builds guns.

Roger5 wrote: ↑

Mon Mar 18, 2019 6:14 pm

Cheers Tony, it would have been good of them to let you know what bar that was at....

I phoned AA after the gun was returned specifically because I wanted to know on what part of the power curve they did their test. I was told it was after the cylinder was filled and a few shots taken to adjust the power. I remember some comment about the setting being within a range rather to an exact specified power level as the latter would require a lot of minor adjustments and retesting - too much to justify.

I wouldn't have thought they took 20 shots to do the adjustment but that's how far into the full 190-100bar cycle I had to go to get up to their results.

I'm guessing AA wouldn't routinely know the pressure at test of any rifle because of inaccuracy of initial fill, differences in the number of shots taken to do the adjustment, and the imprecise/inaccurate gauge on the rifles. I expect they rely on the relative flatness of the sweet spot to be at about the right level.

Surely there would test at the peak of the curve wouldn't they?

John814ce wrote: ↑

Mon Mar 18, 2019 9:24 pm

Surely there would test at the peak of the curve wouldn't they?

Wouldn't need to. Once you know the characteristics of the curve you can, from just a few shots, predict within a few fps what the velocity will be at any position of the curve.

The first thing I did with my S400 was to map the curve so I new what scope/POA adjustments I would need to make according to shot number or indicated pressure.

If you really want to get your head round it:
V = -2E-07x4 - 2E-05x3 - 0.0017x2 + 0.5722x + V1
where V is velocity in fps and x is shot count. V1 is avg velocity first shot