A few of the minor downsides to the M1 over a straight target turret.
1. Less area on the turret for engraving.
2. Larger size makes it more prone to accidental adjustment while traveling in pack or scabbard.
3. Larger size makes optic slightly more bulky and optic takes a few more bangs
4. The Shroud tends to hold debris.
5. No way to cover the turret in situations where you want a cover.
Nothing very earth shattering but I can�t find any advantage the M1 has over the Target Turret
