so many questions FPE, scope etc

[Gibsonvair]

I am developing my cobbled PCP air rifle, It utilizes the 14.6" Lothar Walther barrel in a Crosman  breech and GravMag shooting Crosman Premier Domed pellets at about 770 FPS. The gun is a tack driver at 40 yards punching .250" groups rested. I know these aren't the best pellets, but I like the function of the GravMag. It opened up a lot at 50 yards, so I wonder if a better scope might help. I am currently using a Hawke Vantage  2-7x32 scope. Would a 9 or 12 power scope help, maybe? Or should I make it a 40 yard gun using those pellets? I could use taller scope mounts and shoot heavier, better quality pellets, single feeding. the GravMag comes with a magazine that accepts H&N Hunter Extremes. I am guessing I would have to up the velocity to keep the nice flat trajectory. I shot it today and it went through the same hole at 25, 30, and 40 yards. Probably a 3/8" hole. It started to rain, so I quit, but I am just asking some general questions. I started shooting 18 months ago with a Weihrauch HW 95 and have been playing with Crosmans since Christmas of 2022. I have found the choked Lothar Walther barrels to be more Accurate, but I keep using the cheap Crosman and H&N Field Target Trophy pellets. It takes a lot of time, pellets and data gathering to see trends. It is an unregulated gun so that also throws in some complication in tuning.

[3crows]

You are shooting at 770 fps. My guess is that at longer distance, the 50 yards, the pellets are no longer stable and wander and wobble around. I have noticed similar with my Benjamin 392. It never really gets pellets to their transonic range but at only a few pumps the pellets are also below the speed they may be stable and accuracy suffers. Just a guess that pellets have both a top velocity they are accurate (890 to 940 fps) and maybe a lower limit as well, somewhere below 500 or 600 fps. A pellet may be leaving a barrel at 770s fps and but at nearly 50 yards the velocity is to slow for stability and the groups open up?

[Gibsonvair]

I am waiting on stiffer hammer springs to come in. I cant even utilize a 3000 PSI fill because the velocity is too slow, too low on the curve.  the velocity rises rapidly as the pressure drops and then plateaus around that 770 FPS . A heavier Hammer is in the works for testing also. I am hoping to get the FPS to the high 800's  And then possibly lighten the valve spring for efficiency. Now my chronograph is on the fritz, so I am also waiting on a charger. I have no experience with a gun that I need to tune down, but I would like to. I am hoping. I am having fun learning. My limited experience with my Beeman 2028 showed that more hammer spring preload with more pressure produced a very similar curve but at a higher velocity, Therefor, more power. (Tim Allen grunts)