Memory only, so....... The stock stays on, seems like just the scope rail screws removed and use butt stock (slap gently) to leaver it up. So you end up with the butt stock and reciever in your hand, set aside, just in front of your clip there will be a roughly 1/4" square plastic part with a single screw in the idle of it. Loosen- do not remove-screw and slide SLIGHTLY reward or forward. IF the Koreans Heavy's are still about the same looking at you pick "I" would wait until they arrive t is likely set for them.
Do NOT turn over while working on this. The cycling parts (flat plate on top) is held in only with Thick grease when reciever cover is removed.
No need to degas.
I cant recall what Han's and Ray's "A-Team" web site was otherwise internet archive might pull it up. Back then they made regulators (non-vented) for the Career rifles, golden barrels and in .177 the 1st pre-charged that would shoot an entire FT match w/out refill. Even in .22 and .25 some folks liked them as opposed to EVERY shot lower in fps.
Your speed sound normal for such a light pellet. My stock Career 707II in .25 made 99pfe on the first shot with 39.9g "pelletman" slugs.
The mod many did for pellet shuttle adjust ment was to grind,cut,mill an opening through the receiver (cover) to allow access to that Phillips screw.
Keep us posted,
John
should you own a Ultra they were made to shoot a 76g flat back slug. Tom ("pelletman") provided then to Davis who sent them to the factory, he also sent more to Davis to included free with every rifle. This was the reason so many had cycling and or accuracy issues when using pellets causing people to send them off for "modification". When using the correct ammo the grouped great.
