Although common because it was REQUIRED to promote proper eye relief behind A1/A2 rear sights, following this instruction ensures the shooter is in a relatively weakened position behind the rifle to accept the recoil, because it forces the shooter to blade their shoulders to the target, removing body mass from behind the rifle, and removing ergonomic strength and support from the line of the rifle (aka, linebackers don't turn their shoulders sideways to make hits, they keep their bodies - shoulders and hips - square). Conceptually, think about how far your nose really reaches in front of the plane of the chest... Personally, with my chest square, my nose with my neck stretched as far forward as possible without tilting my head down will only reach 6.25" in front of the plane of my chest... Comparatively, the charging handle of an AR-15 with an A2 stock is 11" from the buttplate... This means I have to turn my head and blade my shoulders to the target to make up for almost 5" of extra length to get my nose on the charging handle... But if I'm not shooting A1/A2 aperture sights, I really don't need to align my eye in that same position...
So instead, with non-A1/A2 type sights, we can realize a more powerful and better supported shooting position, retaining more body mass behind the rifle and keeping our spine better aligned to the target to catch the recoil and run the gun. A shooter can even bring the rifle buttstock inward on the chest rather than slid out onto the medial face of the anterior deltoid, and put even MORE body mass in line with the rifle with LESS leverarm afforded to the rifle to twist the spine in recoil - aka, better catch recoil and recover even faster...
So if you're shooting irons for Service Rifle Competition (and don't, because you'll get gut stomped by all of the dudes running 4.5x scopes now), then nose-to-charger works, but for any other optic, wanting to deliver rapid succession shots on target, stop twisting the shoulders and your body behind and in line with the recoil - which will mean your nose comes off of the charger a LONG ways.
Knowing nothing else, but simply observing their positions, the shooter in
@Ethan Verity's photo will catch recoil and recover on target MUCH more quickly than the shooter in
@Charlie98's photo.
Observing his uniform, and acknowledging the AMU programming, you might imagine Staff Sergeant Payne has been thoroughly instructed on proper operation of the AR-15/M16 platform. But to catch recoil, he’s not shooting nose-to-charger in this photo:
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Alternatively, it’s pretty simple to see how little of AMU shooter Sergeant Wannamcher’s body is behind this rifle to catch recoil, and easy to see how much torque around his spine he will experience when shooting with his nose on the charger.
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