I think your T&C is just not giving full power? Here are my numbers this morning with Crosman Premiers 14.3 22 cal.
Pumps. FPS
3. 433
6. 580
8. 626
At 8 pumps the average Streak is just about the same, maybe a little higher. I asked that question of Streak owners this year on another forum, low to mid 600s
That’s why it will be fascinating to see what your new one will do with a reseal. I’m betting your surprised, it looks to be pretty much untouched? I don’t think I’ve ever seen Chrony numbers for a .177.