Finally got around to it and checked my stock and I have 400 rounds from this lot. I haven't shot any yet but I may do a small sampling to check. That's disappointing.

In my case, I had 500rds of the same lot.
Some of the boxes work fine and others do not. The problem is which are which.

If the blown primers didn't jam my trigger group and/or lock up the carrier group, I would use it as range ammunition.

Quick question for those in the know. As I understand it, the first numbers in the lot number (fc16) is the year of manufacture. Is that correct? If it is, why are all the cases marked with the year of 15? I have two boxes of this lot we are talking about and they are all marked 15. Is there something rotten in Anoka?

It appears that they load it really hot (duh!).

It is discussed > HERE and they confirm it is loaded hot but that does not mean it is defective.
At 3300fps out of a 16" barrel is about 10% too much.
So good lesson is to check ammo or it's specs if you can beforehand.
I understand the frustration, I went thru this on my 308 gassers before I was hand loading.
A lot to learn here.

OK, sometimes I have in the past fell victim to hotter is better. It must be the cool factor or something.
But if I use my batch for self defense, after the first shot and BCG lockup, all I have is a club to fight with.

For practice ammunition, I don't want extra stress on my rifle it doesn't need.

I am thinking either a primer size problem or defective primer pockets. Assuming it is not the firearm, what else about ammunition that would blow the primers.

quote:

Originally posted by orion5:
Quick question for those in the know. As I understand it, the first numbers in the lot number (fc16) is the year of manufacture. Is that correct? If it is, why are all the cases marked with the year of 15? I have two boxes of this lot we are talking about and they are all marked 15. Is there something rotten in Anoka?

I do not find it unusual that a run of brass would be used for loading the following year.

quote:

Assuming it is not the firearm, what else about ammunition that would blow the primers?

Too much or too fast powder.
It's da load!
It's why we chrono and inspect our loads when we hand load ~ carefully in increments.

quote:

Originally posted by lbj:
Assuming it is not the firearm, what else about ammunition that would blow the primers.

When a problem like this occurs out of the blue with a used gun, and especially with ammunition that worked fine in the past and seems to be limited to a specific lot or two now, there’s no reason to believe it’s the firearm’s fault. In fact, when teaching classes on AR-type rifles I ask, “If multiple malfunctions occur with different magazines, and occur with a specific type of ammunition, but not others, what’s the most likely cause?” Answer? The ammunition.

Although the detail and resolution of the photos make me a little uncertain, it appears that the bad cartridge cases show marks indicating that the case heads are flowing into the ejector hole when they’re fired. In addition to the blown primers, that’s another classic demonstration of very high chamber pressures.

As mentioned above, high chamber pressures can be caused by improper loads: too much powder and/or the wrong kind. Primers can affect chamber pressure as well, but I’ve never heard of their having enough of an effect to produce dangerous conditions by themselves.

Something else, however, that can affect chamber pressure is the length of the cartridge case. If it’s too long, the case mouth gets jammed into the rifling and retards release of the bullet on firing.* That can raise pressures to dangerous levels. I would measure the length of the unfired and fired cases and compare the measurements to other ammunition and cases. The maximum case length is also published in loading manuals and elsewhere.

High pressures can also result if the bullet itself contacts the rifling before firing. That’s unlikely with this ammunition, I believe, but measuring the overall length of the cartridge (bullet nose to case head) and comparing that to other ammunition would reveal any problems of that sort.

* The same sort of thing can occur when firing unjacketed lead bullets in some firearms. The lead builds up at the chamber mouth and keeps the bullet from being released properly when a round is fired. I’ve never heard of any sort of similar problem with jacketed bullets in guns chambered for cartridges like the 223/5.56 that don’t headspace on the case mouth. It couldn’t hurt to run a proper brush into the chamber to ensure it and the leade are clean, but if that were a likely cause, it would occur all the time. Many AR shooters don’t clean their chambers and barrels at all, it seems.

Here are some better photos of the Independence/Federal 5.56 brass with blown primers.
I also added them to the intro post on page 1.

I have about 1500 rounds of the stuff still. But, assuming the first two numbers are the year it was made, all mine come from 2010-2014.

I've shot several hundred rounds of the stuff with no issues - which I why I bought so much of it. I guess I won't buy anymore of it - but it's not available in my area anymore now anyway - it was around a lot when the last ammo scare went on.

Thanks; great photos

Definite very high pressure signs, including the case brass flowing into the extractor slot at 7:00 o’clock. The “smearing” of the brass is probably due to its still being back inside the extractor and ejector cuts while the bolt is rotating during the unlocking phase.



I would not fire any of that ammunition in my guns.

I am not shooting any more of this Independence lot I have.
I cannot in good conscience even give them away at this point after the latest photos I took.

I have 13 boxes of 20rds each left.

quote:

Originally posted by lbj:
I cannot in good conscience even give them away at this point after the latest photos I took.

Yeah, I agree.

Any chance of measuring the cases?

Do you mean before or after?
I did some caliper comparison of unspent rounds between the PPU, the 1999 IMI and the Independence and everything was similar, nothing odd found.

The PPU shot fine and looked fine afterwards.
The 1999 IMI shot fine, have slight marks and look to be right at the maximum.
The photos of the Independence tell a different story.

I was primarily referring to measuring the length of the cases before firing in reference to the possibility that excessive length was hindering bullet release and causing high pressure that way. That’s actually less likely than an overcharge or the wrong powder, IMO, but it was something I was curious about.

Mistakes happen.

The OAL are the same between all 3 brands tested.
Also the overall length of the unspent NIB cases of all 3 brands are the same.

The shoulders look similar to my eye but are difficult to measure properly.

What I was thinking about wouldn’t be affected by the headspace (shoulder to case head length), only the overall length of the case from mouth to head. If the headspace length of the cartridges was too great it could prevent proper bolt locking I suppose, but that’s not what’s going on here.

Can you give a box or two to someone who loads and have them pull the bullet and dump the powder?
Then apply a known load?
No sense to waste good components.
They should also take good measurements to make sure the case is in spec.
Then retest.

If a member in the Northern Colorado front range area were to speak up and want them, I would give them to them.

Otherwise, the local PD around here will take unwanted ammunition and either dispose or use them.
I will include some spent cases with them though.
I wish to make certain the local PD is aware of the problem in case they want to use them.

quote:

Originally posted by lbj:
If a member in the Northern Colorado front range area were to speak up and want them, I would give them to them.

Otherwise, the local PD around here will take unwanted ammunition and either dispose or use them.
I will include some spent cases with them though.
I wish to make certain the local PD is aware of the problem in case they want to use them.

I would be interesting to see a few of them fired from a bolt gun, say a R700 with a free bore that runs into tomorrow, just to see whether the exhibit pressure signs as well.

RMD

quote:

Originally posted by rduckwor:
I would be interesting to see a few of them fired from a bolt gun, say a R700 with a free bore that runs into tomorrow, just to see whether the exhibit pressure signs as well.

As discussed in this excellent and comprehensive article, chambers cut to SAAMI specs for the 223 Remington cartridge are usually somewhat smaller in some critical dimensions than those typically found in 5.56mm chambers. That’s the basis for the common belief and claim that it’s unsafe to fire 5.56mm ammunition in 223 Remington chambers. The article points out that the claim is generally untrue, and I regularly fire 5.56mm ammunition in my 223 Remington Tikka T3 myself with no signs that excessive pressures develop as a result.

Despite all that, however, if a cartridge/load shows excessive pressure signs in a 5.56 chamber, I definitely would not then fire it in a rifle marked 223 Remington to see how it did there. I imagine it’s possible that a long freebore might keep pressures down to safe levels, but I wouldn’t bet the rent (or my rifle and eyesight) on the assumption.