TargetTalk

Some russian coaches, while discussing MP 651 as "entry level airpistol" , say that it has too heavy trigger (about 1000 gramm) and if it can be lessen to 500 gramm, the results will be improved greatly. Normally with 1000 gramm trigger pull teenagers can stay in "8" zone, but with 500 gramm they can stay in "9" zone. Can somebody comment this?

General rule, the heavier the calibre, the firmer the grip and the heavier the trigger.
Free pistol light full contact grip and light trigger 55g to 120g.
Air pistol slightly firmer grip with 500g trigger.
Std pistol firm grip 1000g.
Now I know ISSF Centrefire was dropped to 1000g from 1360g, but I found 1000g was too light for
the bigger calibres. With a good good strong grip and 1200g to 1360g trigger, it gave a better control
of shot and recoil.
Service/Action pistol, two handed very positive grip and 2 1/2 to 3 1/2 lb trigger.

Seems true for me comparing how smoothly I can trigger an AP 500g vs firearm 2lbs.

just as a general principle: lower trigger weight = less muscle work = fewer unwanted movements /shaking

If you're putting two equally skilled shooters using the same gun against eachother but you give one of them a 500g trigger and the other a 1000g trigger, the former will usually outscore the latter.