PistolRogue ....I wish I had found this thread earlier!
I purchased an SA17 the same time as my BT4 earlier in the year...and to be honest....I HATED the SA17 at first. I had nothing but problems with the CO2 cartridges and pierce seals (as many other users).
I will admit however...Empire stepped right up with shipping out the parts I needed when I ran out of the replacements lol.
Anyways...long story short, I ended up simply converting mine to a rifle essentially. I machined an adapter myself and used a spare line from another BT (as opposed to buying there rifled kit), and I installed a J&J 14" barrel. Last thing I need to do is hook up some sort of forward grip where the door used to be....but I really want to try a few of your tricks on the sear and bolt.
Here is where I am at as of today (shot consistent 275 on the chrono with the J&J in place after some adjustment). From this: To This:
I am really surprised how loud it is lol.
I have also added a red dot sight on the rear rail, and I have a small 50 round hopper I just need to pick up another BT feed adapter.