What caused my HD ammo to do this?

[Trekbike]

I currently use Federal Hydra-Shok 135g JHP for my house and sometimes carry gun. It's a full size M&P, 40 caliber. I keep two magazines fully loaded and so the ammo just stays in there. When I go to the range I just use different magazines and leave these alone. Yesterday I was doing some dry firing and when I was finished I went to go rotate some of the rounds out of the magazine to keep from chambering the same round again. I started noticing an odd ring indention on most of the rounds. I unloaded both magazines and most, but not all, have this indention. It's not all the way around the case but about 75% around. It appears to be right at the base of the bullet. I'm guessing it's from sitting in the magazine but haven't ever seen this before. I know they weren't like this when I originally loaded them in. The ring doesn't look to be in the same area of how the rounds nest of top of each other on the top rounds but can't tell what happens further down in the magazine.

These are factory unfired rounds and the ring is an actual indention, not just a wear ring. I checked the rounds and they go into my Wilson sizing gauge just fine. Does anyone have any ideas on what is causing this? Do you think they are safe to keep loaded in the magazines? The round on the right is one out of the ammo box that's never been in a magazine.

Edited January 22, 2012 by Trekbike

[TN-popo]

I know they weren't like this when I originally loaded them in.

I think you're wrong here.

I see this quite a bit in just about every box of premium ammo.

I'll let the knowledgeable bullet-builders (I'm not one) explain the hows and whys of seating the bullet.

[Garufa]

It honestly looks to me as the brass was just a little too tight when the bullet was seated.

A magazine will not do that.

[krunchnik]

Looks like the case was too tight on the bullet and when it was chambered it forced it back making it buckle a bit.I sometimes have my crimp too tight and it does that on my reloads.

[Trekbike]

I think you're wrong here.

I see this quite a bit in just about every box of premium ammo.

I'm pretty picky on my ammo and while I might have overlooked and not noticed it on 1 or 2, I would have seen it by the time I loaded 31. I went back and counted and out of 31 rounds only 4 didn't have the indention on the case. The 4 did have the ring marks though. Neither one of us will know for sure since we both didn't inspect them together before they were loaded. I did pull out 2 new unopened boxes from the same lot and none of the 40 rounds had the marks. I did have 2 rounds left out of the same box that were in the magazines and neither had he marks.

It honestly looks to me as the brass was just a little too tight when the bullet was seated.

I would agree that's what it looks like. As I mentioned, I'm picky on my ammo. If I have any show up that look like that while I'm reloading, I cull them out. So if I notice it during reloading, how in the world am I going to miss seeing 27 out of 31 on the factory loads?

I did have some additional things come to mind since I've unloaded and reloaded the magazines a couple of times this afternoon. During my original post I might have made it sound like I loaded the 2 magazines and never unloaded them until today. I have from time to time unloaded them for various reasons. As I mentioned, I like to rotate the rounds to keep from rechambering the same round again.

In the process of playing with them this afternoon, I noticed that during reloading when I push the next round into the magazine the rim of the entering round contacts the other case right in that area. Is it possible that the loading force would indent the case like that? I wouldn't think so but just wondering.

[Trekbike]

Looks like the case was too tight on the bullet and when it was chambered it forced it back making it buckle a bit.I sometimes have my crimp too tight and it does that on my reloads.

So I guess it's possible that maybe since I like to rotate the rounds in the magazine to keep them from being rechambered that might do the same maybe??? I did look at the factory rounds and they don't appear to have a heavy crimp.

[Rightwinger]

I have seen those indentations on rounds from rotation as well. Not uncommon and generally not unsafe unless it causes the case mouth to bell.

[RichardS]

In the process of playing with them this afternoon, I noticed that during reloading when I push the next round into the magazine the rim of the entering round contacts the other case right in that area. Is it possible that the loading force would indent the case like that? I wouldn't think so but just wondering.

That sounds possible to me, especially for the last few rounds that go into the mag where significant force is required to compress the spring. Maybe experiment with a near full mag and load/unload the last couple of rounds several times to see if this happens?