Question about 556 brass


February 24, 2012, 08:18 PM
Been reloading 556/223 for a couple of months now, after loading 45 ACP for 8 months or so. No real problems with 45 ACP but I have noticed a problem (?) with my 556 brass.

I bought 1000 pieces of new, uncrimped Lake City 556 brass to load. I sized all of the brass, trimmed it all, and passed each piece through a Lyman max case gauge before loading any of the brass. As I expected, nearly all of the new, sized brass (except for a handful) slipped easily into the case gauge, and fell out of the inverted gauge.

After loading and firing several hundred rounds using the LC brass, I am finding that after one firing, the cleaned and sized brass often will no longer fit into the gauge. Some of the cases will insert all the way to the rim and stop, as though the diameter of the rim has increased.

I thought that maybe an over-pressure load might be flattening the rim of the case, but I am loading at the very low end of the Lyman/Hornady load data, and do not see any signs of over-pressure on the primers or brass (no excessively flattened, mushroomed, or pierced primers, no ejector or extractor marks on the case head, no signs of imminent (or incipient) case head separation).

Any thoughts on what might be causing this condition?...and is this something I even need to fret about?

If you enjoyed reading about "Question about 556 brass" here in archive, you'll LOVE our community. Come join today for the full version!
February 24, 2012, 08:30 PM
No idea, but having just purchased 500 brand new LC brass, very interested to see what the answer might be.

February 24, 2012, 09:35 PM
Is the shoulder of the case set back properly? And did you Fl resize the cases or neck size only?

February 24, 2012, 09:35 PM
Extractor dings on the rim? Put the head in the gage backwards to check.

February 24, 2012, 09:58 PM

Full length re-sizing. Regular rifle dies (not small base).


I have tried putting the cases into the gauge "head first" and they do not fit, which in my mind eliminated the shoulder variable.

I just found out at another forum I frequent that the Lyman max case gauge may be undersized (apparently a common problem with the Lyman gauge), so I measured the inside diameter three times and got .376, which is .002 smaller than the SAMMI of .378. So you could have a case that was within SAMMI specs that would not fit into the gauge. What bother me though, is that the brass fits when new, I load, fire, clean, re-size/de-prime, and the case no longer fits - so it is changing dimensionally even though I'm using low-end load data.

Edit: I just want to point out that I also checked all of the new brass in the Lyman gauge after loading (before the first firing) and all of the completed rounds fit perfectly. So the change appears to be induced at some point after the first firing. I'm wondering if the case rims are expanding in diameter to conform to the bolt face? That seems unlikely, since not all of the once-fired cases exhibit this characteristic.

Maybe I'm over-thinking this?

February 24, 2012, 10:27 PM
Any thoughts on what might be causing this condition?...and is this something I even need to fret about? If your shooting an AR15 type, the brass has an extractor ding. Remove the high spot with a file to make it fit the gage. Your rifles chamber is the "real" gauge. Does the brass fit the rifle? If so, not a problem.

February 24, 2012, 10:38 PM
Yes, it's an AR15. I haven't checked to see if the cases in question chamber properly. I'll load some up and try. If the rounds chamber and the bolt closes, I'm not going to lose any sleep over it.

Thank you. :)

February 24, 2012, 11:06 PM
See if the FL sized brass will chamber before you load it.

February 24, 2012, 11:30 PM

This not necessary you issue, but something to consider.

I have one full length 223 Rem sizing die that with cases fired in one of my ARs and resize in that particular die, the cases will not chamber in one of my other ARs.

The cases will chamber in the Ar that they were fired in.

I have another full length sizing die that I do not have issues with and I do not have problems with cases sized in small base dies.

I figure that the tolerances of chambers and the die are at the extremes which results in poor chambering.

There seems to be a wide variety of 223 Remington AR chambers out there.

Hope this makes sense.

February 25, 2012, 07:13 AM
I have the same issue with range brass and it's not all LC. They will not fit in the lyman gage but they chamber and fire fine in the AR. Most of the cases that wont fit in the gage have dings or gouges on the rim. I get bored from time to time on cold days and use a small flat jewlers file on the rough spots. If they go all the way down until the rim touches the top of the gage they should shoot fine.

February 25, 2012, 09:21 AM
As I posted on the other forum, your Lyman case gauge is out of spec.

February 25, 2012, 09:04 PM
Here is one possibility.

Brass hardens as it is fired over and over. If you do not adjust your sizer to size a bit more on the work hardened springier brass, it will no longer push the shoulder back far enough, especially if you were barely pushing it back enough with once fired softer cases.

February 26, 2012, 10:46 AM
I had the same problem with a Lyman case gauge in .223 Rem. Sent it back for a refund and bought a Dillon gauge. No more problem.

If you enjoyed reading about "Question about 556 brass" here in archive, you'll LOVE our community. Come join today for the full version!