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Old 01-26-2011, 04:44 PM   #11
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5.56MM brass can absolutely be resized and reloaded to .223 pressures/ specs. The exterior dimensions of the cases are no different. The difference is in the length of the leade (chamber throat). The .223 chamber is usually cut to .085", where as the 5.56 is usually about .162". The shorter leade in a .223 chamber causes higher chamber pressures if 5.56 rounds are fired in it and *may* damage the rifle.

Some 5.56 brass *may* be thicker near the base, but not always. .223 in a 5.56 chamber may adversely effect accuracy due to the free bore.

If a rifle has a really high round count (like tens of thousands of rounds) swapping the bolt into and out of different uppers isn't advisable. For a new bolt and new barrel, the chances of having a head space problem are slim. As JD mentioned, if it bothers you, you can purchase go and no go gauges for your chamber (.223 OR 5.56). They will only tell you that you're head space is within certain parameters. To adjust head space the barrel extension needs to come off and the chamber re-cut or the barrel set back or both, depending.
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Old 01-26-2011, 05:59 PM   #12
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Okay, quick time machine travel back to my first attempted post from last night.

The information thus far has been correct and thanks for the extra explanation Jeeper.

The AR receiver has a shoulder pre cut and all AR barrels (well, 98% of them ) come precut with a lip that fits on that shoulder and your headspace should be A-ok.

Many people will tell you that you can slap an AR together and never worry about headspace. And they are right too, but to a smaller extent.

With the loose tolerances of the chamber ( 5.56mm ) and the fact that people shoot different ammo out of the weapon ( .223 Civilian ) unless you are building a long range, serious target gun or varmint rifle, this minimal space is not going to affect you.

Operator/Mall Ninja A; Builds a 14.5" barreled ( 2" flash hider to make it legal ), clam shell front end, A2 sights, A2 carry handle and his own lower. Head space is not going to be in issue with 95% plus percent of the ammo he is ever going to fire.

Operator/Mall Ninja B: Builds an 18 inch factory, chrome lined barrel, free float tube, muzzle break, flat top, puts a collapsible stock and $650 worth of glass on it. Still not really going to have problems with headspacing. He will be fine with off the shelf.

Tango: Builds a 22", White Oak armament bull barrel, YHM free float tube, BUIS, on a matching billet Upper/Lower with a Leupold fine duplex 4.5 x 14 on Badger Ord rings and has the chamber of the barrel cut to a specific cartridge length/spec in the .223 caliber that he reloads too and wants to use for his varmint gun. Tango makes sure to get his weapon headspaced properly as he is building a long range target model and not a SHTF rifle.

See the difference??
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Old 01-26-2011, 06:21 PM   #13
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So on the .223 what is the part of the cartridge that stops forward movement in the chamber? The length of the case neck?
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Old 01-26-2011, 06:34 PM   #14
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I am not sure I understand the question.

Do you understand the difference between a rimmed and rimless cartridge and how each sits in a chamber?
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Old 01-26-2011, 06:46 PM   #15
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I do understand the difference between a rimmed and rimless cartridge, yes, but how rimless cases sit in the chamber is something I have never really contemplated till this point. Duh for me. I am just trying to understand the importance of case neck uniformity in relation to head spacing and pressure issues, not just case neck tension.
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Old 01-26-2011, 06:49 PM   #16
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Quote:
Originally Posted by Dillinger View Post
Okay, quick time machine travel back to my first attempted post from last night.

The information thus far has been correct and thanks for the extra explanation Jeeper.

The AR receiver has a shoulder pre cut and all AR barrels (well, 98% of them ) come precut with a lip that fits on that shoulder and your headspace should be A-ok.

Many people will tell you that you can slap an AR together and never worry about headspace. And they are right too, but to a smaller extent.

With the loose tolerances of the chamber ( 5.56mm ) and the fact that people shoot different ammo out of the weapon ( .223 Civilian ) unless you are building a long range, serious target gun or varmint rifle, this minimal space is not going to affect you.

Operator/Mall Ninja A; Builds a 14.5" barreled ( 2" flash hider to make it legal ), clam shell front end, A2 sights, A2 carry handle and his own lower. Head space is not going to be in issue with 95% plus percent of the ammo he is ever going to fire.

Operator/Mall Ninja B: Builds an 18 inch factory, chrome lined barrel, free float tube, muzzle break, flat top, puts a collapsible stock and $650 worth of glass on it. Still not really going to have problems with headspacing. He will be fine with off the shelf.

Tango: Builds a 22", White Oak armament bull barrel, YHM free float tube, BUIS, on a matching billet Upper/Lower with a Leupold fine duplex 4.5 x 14 on Badger Ord rings and has the chamber of the barrel cut to a specific cartridge length/spec in the .223 caliber that he reloads too and wants to use for his varmint gun. Tango makes sure to get his weapon headspaced properly as he is building a long range target model and not a SHTF rifle.

See the difference??
So if I understand right, if I have a White Oak .223 varmit upper assy., in order to get good groups @ long or short rsnge I need to shoot .223 ammo? And the same if it were a 5.56 + 5.56 ammo? Is this correct?
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Old 01-26-2011, 07:15 PM   #17
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Quote:
Originally Posted by Squirrel_Slayer View Post
I do understand the difference between a rimmed and rimless cartridge, yes, but how rimless cases sit in the chamber is something I have never really contemplated till this point. Duh for me. I am just trying to understand the importance of case neck uniformity in relation to head spacing and pressure issues, not just case neck tension.
Okay so you understand on a rimless case that shoulder is what is set against the tapered chamber of the barrel and that the bullet itself is free floating in the chamber and not jammed right into the lands and grooves. Correct?

When you hear of shot cases being "fire formed" what is happening is that the pressure, and heat, on the brass is expanding rapidly to push the walls of the cartridge case against the chamber that was cut by the barrel reamer.

Generally it (your chamber) will be just a couple of thou off/over the spec of the round so that you can get the catridge in and out.

Too much pressure causes the brass to misshape in the chamber and is one of the things that cause a case to get stuck after firing.

In an ideal chamber, the brass is a perfect fit around everything but a small portion of the area right around the bullet, before that bullet enters the lands and grooves to generate rifling and transfers that explosion of primer and gunpowder into torque.

Improperly applied, the explosion of primer and gunpowder creates gas that has time to push the bullet forward, but also build up back pressure as the round that is traveling straight is forced to start rotating. Too much pressure and you get a blowback situation.

This is one of the key reasons you hear of locking lugs and lug lock when talking about quality rifle actions. If those locking lugs are not tight against the action, or weak in any stretch, that pressure has to go somewhere.
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Old 01-26-2011, 07:17 PM   #18
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Quote:
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So if I understand right, if I have a White Oak .223 varmit upper assy., in order to get good groups @ long or short rsnge I need to shoot .223 ammo? And the same if it were a 5.56 + 5.56 ammo? Is this correct?
At the very basic level, yes, you are 100% correct.

You have to define "good" groups and you also have to factor in harmonics and outside influences on the barrel in question. Not to mention the lock up between the bolt face and the chamber, but yes, you are correct.
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Old 01-26-2011, 11:56 PM   #19
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Couldnt he go w/ the Wyld (spelling) chamber for better accuracy over the board?
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Old 01-27-2011, 12:38 AM   #20
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Couldnt he go w/ the Wyld (spelling) chamber for better accuracy over the board?
Yes. I was waiting who would ask that question first. Cupie doll for you.

Here's the problem with the Wylde. It allows you to shoot both 5.56mm and .223 with reasonable accuracy. However it shoots NEITHER of them with great accuracy until you fire form some brass and reload for that specific chamber specs.

Now the same can almost be said to be true for any 5.56mm rated chamber, except that it will give better accuracy for it's 5.56 round and slightly less accuracy for the .223 when compared to the Wylde.

Since 5.56mm is FAR more common across the mainland of our current occupied terror-tory, it is the smarter choice in MY humble opinion.

YMMV

JD
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