"Marksman barrel" makes the Gen5 more accurate than any other generation according to Glock themselves. From Glock
https://us.glock.com/en/learn/glock-pistols/gen5:
"GLOCK Marksman Barrel (GMB) features a more aggressive polygonal rifling with a target-style crown and tighter chamber specs, which delivers improved accuracy."
Any google search seems to confirm by all makers (alienwear, bravo concealment, guns.com, etc)
Here is the Brian Enos forum asking the same question:
https://forums.brianenos.com/topic/2...more-accurate/