I’m trying to confirm if a barrel is a factory or aftermarket. It’s a 4.5” Gen I barrel that’s supposedly factory. Can someone take a pic of theirs with the flash hider attached, from the side of the handguard? I’m trying to determine how far from the front of the handguard it should protrude. Also, what markings are on the barrel? This one only says “9mm NATO” unlike my 8” Gen I barrel which says “9mm NATO 8” in a distinctive Sig lettering.

Got both 8" and 4.5" gen2 factory barrels/handguards. Markings are exactly as you said, with the "9mm NATO" marking running along the length of the 4.5" barrel, while the fancier "9mm NATO 8" marking runs around the circumference. With the flash hider tightened down on the shorter barrel, it extends exactly 1 1/8" from the handguard edge. Hope this helps.