So we all know the classic scene in Apocalypse Now where the soldier (I think I got that right, Air Cav, right? or were they Marines?) taps the M16 mag on his helmet. As I kid I remember asking why he did that. My uncle told me it was to clear out any sand or dirt than might have found its way into the mag, but he also said it was to seat all the cartridges all the way flush to the back. He said it would result in less feed issues. Is this true?

I ask because I just bought a new Glock 43, and after I rack a round and drop the mag, the next round is no longer seated all the way. Is this cause for concern?

It shouldn't concern you, it's a glock.
Just shoot it.

Many guns will do that, the bolt dragging over the next round in the magazine has enough friction to carry it forward.

Provided it's not an issue, don't worry about it. The round will probably get dragged back when the bolt cycles.

Often when loading double stack, double feed magazines, they will inevitably get bumped forward. A tap of the magazine spine on the wrist/helmet/table/tailgate will seat the rounds back and allow easy loading and feeding.

I've yet to have an issue with it, but I always smack my magazines at least after loading. Unless loading administratively, I don't look at the mag or smack it. Exceptions being when I've fumbled a mag into the dirt. Ones kept in a pouch outside extreme conditions should not be problematic.

When in the field, provided you can spare the noise and time, it would be cheap insurance.

I only do it if there is a round seeming to raddle inside the magazine. Seems to happen on my AR and Glock mags and sometimes AK mags. A firm smack usually gets rid of it.

It has never seemed to be a factor in reliability.

I’ve had no combat experience but I thought tapping the mags dated back to the straight 20s with the tilt followers. If mags were dirty or springs were weak a tap on the side of the helmet usually cleared them. But I thought that went out with the anti tilt followers and 30 round mags.

Never heard of any Mil or Leo training advising of rapping M9 or Glock pistol mags. Is that a thing?

My Dad served in Vietnam and only mentioned tapping AR mags, never for any other platform. Only time I ever saw it improve feeding was running 5.45x39 thru straight GI 20s but never had mag rattle with 5.56 or .300bo.

I’ve always tapped the back or bottom of magazines before I load the gun. I obviously think it makes a difference.

That’s how my Dad taught me back in the ‘70s. I do it, it makes me feel better.

Although, I have learned NOT to do that with some of my .22LR mags. A couple times I believe it caused a rim over rim malfunction.

ETA- Dad was a Vietnam Vet.

ETA2- I don’t wear a helmet. I just smack the back of the mag against the palm of my hand.

I might start doing it.

I did a carbine class recently using nothing but Wolf steel case, and had one failure the entire class- two of the rounds in my Pmag, about 10 rounds down, managed to wedge themselves directly next to each other like two fat guys trying to fit through a doorway.  All the rounds above the jam looked normal, but didn't have any spring pressure feeding them upward.

This was NOT a failure that I've ever covered in a malfunction drill, and I definitely spent way too long repeating the typical clearance approaches before just dumping the mag.