Air Arms Owners Club

Very interesting - with springers, it's usually about ensuring stock screws remain tight, but this is not the same. I will try something like that with the one I have.
I'm getting a spring and other parts from Julian too. Will let you know how I get on.

Chuck Glider wrote:OK, a bit more of an update. After a bit of hacksawing, I managed to get the choke cap off as well. So, I've reassembled the gun with the following settings compared to original (remember it was at around 10.4 ftlb with RWS CO2 Target 7gr pellets):

-- hammer spring, 1.5 turns less tension
-- choke, 3.0 turns opened up

Tomorrow I may be able to Chrono test. With a bit of luck it will be around 8ftlb, so then I can close up the choke a bit to get it to 7ish ft lb.
...

So, I did some chronographing today and it went very smoothly. I think Raj must have been right about this hammer spring being a 7.5J one already. With the venturi choke fully open, I was getting around 8.5 ft lb initially. I didn't adjust the spring any further, but just the choke. Basically as I wound the choke in took over 2 turns before it started to have any effect. Then it was fairly easy to adjust it to about 7.5 ft lb with JSB Exact domed 8.4gr. This setting seemed to give around 6.6 ft lb for the 7.0gr RWS Hobby flat heads.

I'll leave it there for now. Will do another power curve when I get some time to see how many shots I'm now getting out of it and where the sweet spot is.

I would back the hammer spring out a bit more. Rog

Roger5 wrote:I would back the hammer spring out a bit more. Rog

Thanks Rog, but why?

8.5ftlb is still a bit high, I would back out the Venturi screw again, and use hammer adj to bring the the power down some more, if you can get it down to where you want it, it's better then choking it.Rog

Did another power curve with pellets I had to hand. Plotted below on the same chart as the previous data. For both of these, the start fill was ~190bar. The fill at the end of the red data was ~90bar, and ~85bar at the end of the blue data. All these pressures were measured on the Hills pump that I use to recharge the cylinder.

I find it very interesting. It seems that lowering the power of the rifle spreads out the curve, as the data shows. That means that what Rog suggested, lowering the power a bit further, is definitely worth trying - it may give even more shots at a consistent speed.

Nice big sweet spot !!! Result

Raj, yes, I was surprised by the impact of the power change. I'm going to have another go to get the pellet speed down to around 580 fps, as I understand that's optimum for target shooting at 10m, with flat head pellets. The Rowan Engineering jewelry arrived today - see photo. I didn't want to spend so much on it, but having seen the fine quality in real life, I feel ok about it now. They look amazing, beautifully made.

The trigger will make a huge difference to your shooting accuracy.

Raj wrote:The trigger will make a huge difference to your shooting accuracy.

Um, Raj, I have to ask:

1. Are you joking about the trigger or serious?

2. And does this mean that you think the brass support will be detrimental?