Quick update on this ....

The original trigger screw on my gun is 8.9mm long including the head which is2.1mm so an effective length of 6.8mm

The screws I got from an engineering supplies store are 18mm long with a 2mm head - so 16mm of thread depth.  The one I cut down is 10.7mm long, so 8.7 mm thread depth.  I have since added a .7mm spring washer and am happy with the result.  Still has a long first stage but much cleaner break than the standard trigger.   

I went to the place kruza mentioned in Hastings this afternoon and bought 4 20mm long screws for less than $1 each and a few small spring washers.    Cut one down with a hacksaw to just over 10mm and then tidied the end up with a file.  Huge difference to the trigger.   Very long first stage then a clean break on the 2nd stage with no noticeable creep.  I may dismantle the trigger unit and polish the components at some point but will need to test a lot more first.  I did find a YouTube video that went through the the process and showed where to polish the bits of the trigger unit, but cant find it right now.   If I do end up doing this, I may need to either add a spring washer of shorten the new screw slightly as I suspect polishing everything may make the trigger too light.

At less than a dollar and a bit of time this was way better than buying an off the shelf screw kit for the  Gamo SAT as listed here ..

https://www.guncity.com/gamo-trigger-job-screw-for-s.a.t.or-c.a.t.trigger-385159

For that sort of $$ you could just about get one of these which are supposed to make the trigger much better again.

https://www.charliedatuna.com/GRT-4G.htm

Hopefully I will get time to fully test tomorrow - Only problem is that if it is good as the first few shots indicate, I may need to get one of these ...

Just text me on 0275 780 780.

Thanks for the thought - but I know you are working long hours for the next few months.  I did have a look on there web site and is says they have several lengths of 2.5mm machine screws in stock.  As I will be putting my car through the touch free car wash at the Caltex in Omahu road, I'll probably just call in and see what they have.  

Crono is reasonably consistent 704.2 - 715.2. I really need to strip the gun down, clean and relube.   I got it 2nd hand from a guy in Stratford and I have no idea of it's history.  I did clean the barrel out when I got it and it was quite dirty.   I have put close to 300 pellets through it and it is still dieseling after every shot.   My son-in-law has a 177 gamo he bought new and it was diesling a little last time he used it but it has probably had less than 50 pellets through it.   It also has the SAT - so I'll grab a few screws if they do have them as they are under $1 each and  if I can make my trigger work better I'll have a look at his too.  I've only shot his gun a couple of times and  can't really recall much about it.

Thanks for the update -  Looks  like I'll be  going to Hastings, probably Tuesday so Ill check it out then.   I am aware of the plastic roller - it fell on to the floor the first time I took the stock off my Gamo - had to find a video on YouTube to work out where it came from LOL.   I have seen some info on smoothing/polishing the sears which one person reckoned it made a big difference.    One  of the "longer screw" videos found an 8mm didn't make much difference but a 10mm made it dangerously light so he used a couple of small spring washers which effectively reduced the screw to about 9mm.

Anyway - worth a try to hopefully get better consistency out of the Gamo.