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 ...

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

Thanks Rog, but why?

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,...

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.

Very, very expensive, but can I resist a brass support bracket...

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, ...

Here's an update. It was easy to get the hammer spring cap nut out. After marking the cap nut on the side nearest the grub screw, I gripped the pin in the middle with long nose pliers and turned it out quite easily. Took 3.5 turns until it was flush with the receiver block, so I know how deep to put...

Thanks Raj. That helps a lot! I was also wondering about those side grub screws, so thank you for explaining that as well. Assuming I manage to get that main spring bolt moving, then should I move that only, or also the venturi? I find it interesting that the venturi is placed to be accessible with ...

I agree Rog, or the lighter hammer spring. However, how can I do that? There's no slot or Allen key hole...

So I tried clamping the rifle in a workmate with leather faces, and shot some 5 pellet groups. I used Gamo Match and JSB Exact (which are marked 4.5 on the tin, but 4.51 on a sticker underneath). The first photo is of that. This shows a 5 pellets going in the same hole using JSB Exacts. I'm chuffed ...