Today definitely didn't go as planned. I was really hoping to start a new thread here that would be a deep dive into some chrony work and efficiency testing. I had brought the gun outside early to acclimate to today's 37f degree temperatures and right at the end of my first magazine I pull the trigger and ....
>>>>> POOOOM! <<<<<<<
(Insert the sound of the inner barrel o-ring blowing out.)
CRAP.
Well, I had been meaning to take the barrel off but this was not my ideal time. Oh well. I bring it inside and take of the side plate to expose the barrel clamping screws and I see this... the cocking link separated. This was causing the probe to not seal as it should (and sound like a blown inner o-ring):
To make a long(ish) story short, it wasn't a hard thing to fix, but I took my time, took lots of photo and some video, got it back together, adjusted it properly and the gun is shooting well again today.
Either the grub screws backed out a little bit and allowed the linkage to come apart, or the linkage wasn't inserted quite far enough and grub screws were not seated in that little groove in the linkage arm.
Here's the flip side of today ----> HOLY COW, IS THIS GUN ACCURATE!
Here are a couple of closeups of 50-yard / 5-shot groups. These were with JSB 18s.
And here's the full target (such as it is). The top row are groups shot just before the linkage separated (which was what I originally interpreted as the barrel o-ring going).
In fact, I think that top right group was opening up as the linkage was coming apart. You can see my note on the bottom row where I thought the breech seal blew. The yellow, green and purple stickers were all 5-shot groups with the gun sounding good and strong again.
So all's well that ends well