Gamo trigger guard

Oh by the way i did not have a trigger guard. If you no longer need it might be a good idea for me to move this topic over to the technical section as there seems to be a lot of good information here.

With the crappy weather over the weekend I have done some more work on the Gamo Hunter. I put the stock back on and fired a couple of shots out the porch, only got 500 fps with jsb exact .177s - bugger.
So I took it apart. Seal stuffed. Put a new seal in. Now got 800 fps much better but not awesome. Breech seal looks ok, Hmm, I'll have to try a different spring or a gas ram.
Then I noticed the barrel was not locking securely in place. Just waving the rifle around or a gentle tap on the barrel was enough to make the end of the barrel drop a few mm's. This will not do, I thought. Google is disturbingly silent on this topic. Oh no I'm going to have to think for myself like the old days.
I can see 3 things that could cause this problem.
1. The latch spring is weak.
2. The latch faces have worn.
3. The barrel lock up in place has always been crappy.

I decided that angle the latch faces meet (due I expect to 2 and 3 above) was wrong and made it too easy for the latch to pushed in.
I think I will need drawings to explain, but I ended up modifying the angle of the spring latch in the breech and the shape of the fixed latch on the front of the compression chamber.

Now it's sweet as, the barrel/breech stays put until you give it a firm slap to break it.

Hi nunga
I ground the existing sprung pin to have a shallower angle. I also noted that the crusher and Diana have a different  type of fixed pin. That is the latch pin contacts a circular surface. A ball bearing on the Diana and a round bar on the crusher. This seemed better to me. So I modded the fixed pin in the compression tube to have a semi circular surface. I could not remove the pin to make a replacement so I added a spot of weld with my tig an then filed and sanded it.