.223/5.56 case lengths

[bigjake]

There isn't a forum for just plain brass. This isn't about forming cases, so I came here.

I collect a lot of range brass. most of the rifle brass is .223/5.56 The thing is factory cases vary in length by a lot and I don't understand why.

I find a lot of FC brass. Its the shortest. It can be as short as 1.730. I just picked up about 300 WCC once fired brass. It was long, like 1.770 not all of them that long but long none the less. These cases aren't cheap commercial ammo. it is military ammo, the primers are all crimped, the projectiles are crimped. and there is NATO markings on them.

Why do these cases vary in length so much? They go off, they don't misfire. All the preaching about case trimming!? why do we bother to trim? It seems soldiers don't need common sized cases for their ammunition.

[243winxb]

Why do these cases vary in length so much? Difference in rifle chambers headspace is one. Chambers can be .015" longer than others, if with in specification . The other is some come from the factory at the minimum of 1.730" others may be at maximum of 1.760" before being fired.

[bigjake]

I can see your second reason, but what does the chamber have to do with the Federals' and Winchesters sorry specs.



Difference in rifle chambers headspace is one. Chambers can be .015" longer than others, if with in specification . The other is some come from the factory at the minimum of 1.730" others may be at maximum of 1.760" before being fired.

[runfiverun]

the cases stretch to fill out the chamber under pressure.

also if the timing of the powder is off a bit in an AR type rifle the case is still gripping the chamber walls while the extractor is jerking it out.
this will stretch the case a bit.

[243winxb]

http://www.saami.org/PubResources/CC_Drawings/Rifle/223%20Remington.pdf On firing, the shoulder of the cases stretch filling the rifles chamber. The difference between a tight and loose chamber is .015" Add this to the factory brass length that are as much as .030" = 1.775"

[GabbyM]

Much of the old Federal had short cases. Not a big deal because by the time you FL size down a case that was fired in a 5.56mm NATO chamber it will be over length and need trimming.

We trim cases for two very serious reasons. First just for consistency. 2nd because the chamber is cut with the case neck at a given point. If our case gets long it will be swaged into the bullet by the neck throat juncture causing high pressure from holding onto the bullet. If you load for just one rifle. You can buy a gage to measure just how far your chamber is cut then make your case length off that. Going to that trouble for an AR or any other gas gun is a joke.

For my AR's I use an RCBS X die set up and follow those directions. Works out great so far.

[Jupiter7]

Factory FC brass is still short, can fire multiple times before needing trimmed. Not sure why, but confirming anyhow. Winchester (WCC 5.56) usually needs trimming after firing factory loaded ammo in my experience, regardless, this is my favorite brass for full house 5.56 loads in my AR's.

[Larry Gibson]

Much of the old Federal had short cases. Not a big deal because by the time you FL size down a case that was fired in a 5.56mm NATO chamber it will be over length and need trimming.

We trim cases for two very serious reasons. First just for consistency. 2nd because the chamber is cut with the case neck at a given point. If our case gets long it will be swaged into the bullet by the neck throat juncture causing high pressure from holding onto the bullet. If you load for just one rifle. You can buy a gage to measure just how far your chamber is cut then make your case length off that. Going to that trouble for an AR or any other gas gun is a joke.

For my AR's I use an RCBS X die set up and follow those directions. Works out great so far.

GabbM nailed it. Neither brand is "sorry" nor out of spec for 5.56 NATO. That falling within the established "spec" for 5.56 case length does not meet our reloading criteria is not one of their concerns......they could care less.

Larry Gibson

[bigjake]

I know why we trim. I just thought the military would want their cases accurate. FC cases are short to begin with. WCC cases are long from the factory. I just wanted to know why, and I found out, their within the governments specs.



Much of the old Federal had short cases. Not a big deal because by the time you FL size down a case that was fired in a 5.56mm NATO chamber it will be over length and need trimming.

We trim cases for two very serious reasons. First just for consistency. 2nd because the chamber is cut with the case neck at a given point. If our case gets long it will be swaged into the bullet by the neck throat juncture causing high pressure from holding onto the bullet. If you load for just one rifle. You can buy a gage to measure just how far your chamber is cut then make your case length off that. Going to that trouble for an AR or any other gas gun is a joke.

For my AR's I use an RCBS X die set up and follow those directions. Works out great so far.

[warpspeed]

Mil spec / NATO spec stuff is designed to be shot through either a M4 , M16 or M249 and the result is a case that is almost always on the upper end of the spec. They want the max neck length possible to insure the bullets have enough neck tension for those rounds that are not crimped on the canalure. Also, the same case is used for blanks and I'm guessing the longer neck might be better for that.

The commercial stuff, especially the FC headstamp, always seems to be close to the SAMMI minimum spec.

[Larry Gibson]

I just thought the military would want their cases accurate.

bigjake

Therein lays the difference; they make the cases "accurate" enough to meet their accuracy requirements.....not yours.

Larry Gibson