so after this new factorio update the cannon turrets seems to not be hitting their max range with the regular cannon shell (they are fine with any other shell that doesnt have a range modifier stat)

https://imgur.com/a/7WtszZH
Heres an image of biters gathering inside of cannon shooting range but the shells never hit as they expire way before hitting the biters.

I'm going to download few recent versions and test when this started happening. This might be a vanilla bug.

EDIT: Those scattergun turrets in the screenshot will kill your flamers if biters get in range - shotgun pellets do friendly fire. If you want to use them, they need to go in front of the wall.

Found it. Since version 2.0.24, turrets receive the range buff from ammo range modifier (they didn't before). However, when turret uses target leading functionality, it causes a bug and projectiles detonate at base max turret range. This is a vanilla bug, I'll make a report on the forum. However, since Christmas is so soon, I don't expect this bug to be fixed until after New Year's. I'll publish an update to remove the range buff from the shells for a temporary fix until devs release the bugfix.