Odd dent on 5.56 cases.

[Ozzieman]

Odd dent on 5.56 cases.
A good friend just gave me 200 once fired cases. These are PMC and were new in the 20 round boxes so they were pristine when he shot them.
His gun is a new Bushmaster copy of the M4 and these were the first shot out of the gun.
The odd thing about the cases is that about 20% have these small but deep dents. When I asked him about the gun from what he said they were ejecting what I would consider normal and it was on grass so the chance of them hitting anything on the ground was very small.
This is not from the cases hitting the gun because most had the small dent from hitting the deflector just aft of the port.
Any one seen dents like this?
Thanks

[Kimber84]

Probably the brass deflector smacking them on the receiver. Mine both do the same thing.

I've heard of ppl trimming the ejector spring to throw them more forward. Dunno though, never tried it and never cared that much, next firing they disappear and a new one shows up elsewhere on the case.

[Geezerbiker]

There could also have been a piece of grit in the chamber that came out with that case.

Tony

[Metal god]

if the dent is in the same place on all the cases i'd say there is something up . What that is , I really dont know . check the chamber for a bur or something esle . check around the ejection port area for something they might have been dinging off of . not sure I'd reload those . the walls are pretty thin up there .

keep us updated i'd like to know what you find out .

[Rikakiah]

I got 2 entire boxes of "new" Winchester ammo with dents pretty exactly like that on every round.

[Metal god]

^^interesting^^

I would not think that would slip by QC but could happen . Maybe even more so with how hard it is to get ammo . They could be letting things get by that normally would not .

[Ozzieman]

Probably the brass deflector smacking
I don’t think so, many of the cases have the larger dent but much more shallow from the deflector. There is nothing on the deflector that will make a sharp dent like this.
piece of grit in the chamber
I would think that you would see some kind of stretching of the dent on the case from extraction. It could be your right but 20%?
if the dent is in the same place on all the cases
The dent is the same distance from the case mouth. I suggested that he fire a number of rounds dropping each in the chamber and mark the back of the case so he knows where the top of the case is on each firing.
You know, you guys just got me to thinking. What is the possibility that the case is hitting the deflector and some of them are rotating forward and hitting the small bar that sticks out from ether end of the ejection port cover??
As far as reloading them, rest assured they will end up in the scrap bucket.
Thanks for the great ideas.

[Coach Z]

I've seen some of my spent brass with a dent in that location but longer, I'd call that a dimple I guess. Have a look at the gun that he shot it from and the shell deflector as has been mentioned. Also if it is a carbine length gas tube that can make for a more violent ejection and lead to more heavily dented cases.

[Kimber84]

Originally Posted by Ozzieman

As far as reloading them, rest assured they will end up in the scrap bucket.
Thanks for the great ideas.

Send them to me!

[Sierra280]

Pretty sure it has nothing to do with the gun.

I think that is some sort of manufacturing mark on surplus ammo, it's more pronounced on some cases and not detectable on others. I went digging through my stash of plinkin' ammo, the one on the left is headstamped hp 76, the right is fnm 80-60. Again, not noticeable on all (or most) maybe in the ballpark of 10% +-5, I wasn't about to sort through it all.

I did not see any marks like this on the LC stuff or on the annealed SB ammo.

These are 7.62 BTW.


Aaarrrrggghhh, can't get picture to upload, will try again tomorrow, or would be happy to e-mail it to someone who knows what they are doing (apparently I don't)

[Sierra280]

There we go

[Ozzieman]

Sierra280 thay are not as deep but it sure looks just like them.

[Sierra280]

Same place too (on the fnm NATO ammo). It's worth noting all the fnm that has that is in the same place, other manufacture has it all on the same place too. What is the headstamp on the brass you are finding it on?

Edit-nevermind, you said pmc, sorry. Anyone else seen this??

[Sierra280]

Had a couple boxes of PMC bronze 147gr nato. same thing on 3-4 per box (about 20%).

Now I'm positive it is a manufacturing mark, as this stuff is less than a year old, new in box.

[sc928porsche]

Usually dents in loaded ammo are straightened out when fired in the chamber. Sometimes you can get a little too much lube on the case when sizing and put "oil dents" in them. They disappear when when fired. Your cases are probably hitting something when extracted.

[Sierra280]

I will try to post a pic tomorrow,the PMC ammo, like the NATO ammo, I've seen this mark on new, unfired ammo; definitely not the extractor. But once you blow it out, just full length size, fine to reload.

[Geezerbiker]

Those look like gunpowder dents from powder spilling in the loading machine.

Tony

[Hummer70]

I suspect it is from a ejector rod knocking the loaded round out of loading machine. I wouldn't worry about them.

[Buzzard Bait]

stepped on or damaged some way on the ground after it was ejected?
bb

[Ozzieman]

Ground damage?
Possible but 20% of 200 and all within several thousandths of an inch below the case mouth doubt it.

[Sierra280]

Did my pics not post??!! I have UNFIRED NATO ammo with the same mark, pretty much takes the ejector/extraction/chamber marks out of the equation. So we still don't have any answer. Except hummer70's theory.

Edit-I'm still not worried about it especially since its mostly berdan primed ammo (which I always bring but usually only shoot when there are brass scavengers at the range, lol)

[SteelChickenShooter]

One way to test metal hardness is to apply measured force with a small ball then measure the diameter of the dent it makes. I wonder if that could be a possible answer?