Yea my JP is by far my smoothest gun i own. Its not by a little either. Paired with their "roller" trigger its definitely my fastest split times. Pure magic what they do at JP. If i had the money i would buy the LRP in 6.5cm.I have a few, and love them, definitely quieter in my rifles. I usually get the spring kit with mine, and like the ability to tune them.
I have one in combo with an adjustable gas block, and it's easy for me to make a mess out of if; as soon as I think it's reliable for 855, I change ammo, go back to 855, and it's not cycling. I'm sure it's user error, no previous experience with adjustable gas blocks.
The complete JP system with bolt is first class as well, but I like just the spring set for the money.
ETA all 5.56.