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Posted: 11/2/2009 9:57:17 AM EST
Hey there guys, I recently gained an interest in building a retro rifle and am trying to figure out how to go about this project, there are alot of great resources here.

Few questions:

I have been told that 5.56 barrels can shoot .223 but not vice versa, were all retro M16s 5.56 or were there different variants? Im just confused on what route I should take between 5.56 / .223

some parts kits out there have barrels "in the white" that require machining where can I look for individuals that can finish it for me?

Thanks,
Link Posted: 11/2/2009 10:17:52 AM EST
If you are referring to the Century arms kits,(Barrel in the White) For the price, you can check the EE here (Best Bet) and find a complete Original USGI Upper with Original USGI Barrel. and still have money to buy other components.

You cant shoot 5.56 out of a .223 marked rifle because the .223 chamber has tighter tolerances and i believe the neck is longer on a 5.56? if im wrong i'll be corrected

Not sure if any Military rifle was designed just for .223 although you will find lowers and Mags marked .223

Ethan
Link Posted: 11/2/2009 10:45:01 AM EST
It's my understanding that Colt does not differentiate between .223 and 5.56. You can use either. .223 markings on Colt magazines and lowers shoot either. If you are using another manufacturer you want to be sure.

I saw a C MP C barreled 604 upper on the old EE last night for a great price. Check in the used parts section.

The kit that requires finishing off the barrel looks like it is more trouble than it's worth considering you can still find original parts for decent prices.
Link Posted: 11/2/2009 11:09:36 AM EST
thanks for the replies guys, ive been trying to get in contact with gunnyssurplus regarding their usgi m16a1 uppers to determine if it is 5.56 or .223 but no luck, do most people put effort into getting a true 5.56 barrel or is settling for a .223 acceptable?
Link Posted: 11/2/2009 11:28:08 AM EST
The Gunny's one is an original and it's 5.56.

It's really easier to find a 5.56 than it is to find a barrel that shoots only .223, especially when dealing in retros. Any Colt barrel is going to be 5.56 and the commonly used Bushmaster LW is also 5.56. I'm sure you could run across an A1 profile barrel that is only .223, but that would be unusual. (I can't think of any right now, but someone will know if they even exist).
Link Posted: 11/2/2009 11:29:54 AM EST
And welcome to the site!
Link Posted: 11/2/2009 11:49:33 AM EST
[Last Edit: 11/2/2009 11:52:07 AM EST by MarkRSims]
Hornady Website:
What is the difference between 5.56 NATO and 223 Rem ammunition?
Differences between the two are small but can have a large impact on performance, safety and weapon function.

The first difference is the higher pressure level of the 5.56 NATO cartridge which runs at approximately 58,000 psi. A 223 Remington is loaded to approximately
55,000 psi.

The second and most important difference between the two is the fact that a 5.56 NATO chamber has a .125” longer throat. This allows approximately one more grain of powder to be loaded into a 5.56 NATO cartridge; this is what gives it higher performance than its 223 Remington cousin.

The biggest problem with these differences is when firing a 5.56 NATO cartridge in a rifle chambered for 223 Rem. Due to the longer throat that the NATO chamber employs this combination will cause a 223 chambered weapon to run at approximately 65,000 psi or more. This is 10,000 psi higher than the 223’s normal functioning pressure of 55,000 psi. This is NOT safe and will cause primers to back out, or worse, cause harm to the operator, the rifle, or both.

The reverse of this is firing a 223 Rem cartridge in a 5.56 NATO chambered rifle. Due to the throat difference between the two chambers a 223 Rem cartridge may not work optimally in a 5.56 NATO chambered weapon. The cause of this is the lack of pressure built by a 223 Rem cartridge fired from a 5.56 NATO chamber. The 223’s 55,000 psi will not be attained and therefore velocity and performance are hurt. Problems start occurring when this combination is fired out of a 5.56 NATO chambered rifle with a 14.5” (or shorter) barrel. The lower powder charge of the 223 round coupled with the pressure drop that occurs when it is fired in a the 5.56 NATO chamber will cause the rifle to cycle improperly. NATO chambered rifles with barrels longer than 14.5” should function properly when firing 223 Rem ammunition.


That all being said, all of my AR's are marked 5.56, or have military barrels and I've run commercial .223 through each of them at one time or another with no problems.

'Course, then you can get into .223 Wylde chamberings too. But that's another story.

ETA: OH yeah! Welcome to the site!
Link Posted: 11/2/2009 1:18:48 PM EST
No one can ever come up with an example of a rifle suffering any damage because of .223 /5.56 mixup.

Not one on repeated challenges. Go forward and don't worry
Link Posted: 11/2/2009 1:39:42 PM EST
My understanding is that 5.56 and .223 'Wylde' chambered rifles can handle both 5.56mm and .223mm ammunition without any problems.
That said, assuming that your bolt locks up OK with 5.56mm ammunition in a .223 barrel, I doubt that it would cause any problems. My understanding is that AR-15 type rifles are usually marked ".223" purely for political reasons.

HOWEVER...If your rifle was a civilian marketed sporting rifle, THEN I would consider looking into the details much more closely.
Link Posted: 11/2/2009 1:57:09 PM EST
Originally Posted By Der_Hans:
My understanding is that 5.56 and .223 'Wylde' chambered rifles can handle both 5.56mm and .223mm ammunition without any problems.
That said, assuming that your bolt locks up OK with 5.56mm ammunition in a .223 barrel, I doubt that it would cause any problems. My understanding is that AR-15 type rifles are usually marked ".223" purely for political reasons.

HOWEVER...If your rifle was a civilian marketed sporting rifle, THEN I would consider looking into the details much more closely.


Stay up all night tonight trying to find 1 documented example of a rifle failure caused by 5.56. Then tomorrow don't try to scare people anymore
Link Posted: 11/2/2009 2:05:07 PM EST
Originally Posted By ranchhand:
Originally Posted By Der_Hans:
My understanding is that 5.56 and .223 'Wylde' chambered rifles can handle both 5.56mm and .223mm ammunition without any problems.
That said, assuming that your bolt locks up OK with 5.56mm ammunition in a .223 barrel, I doubt that it would cause any problems. My understanding is that AR-15 type rifles are usually marked ".223" purely for political reasons.

HOWEVER...If your rifle was a civilian marketed sporting rifle, THEN I would consider looking into the details much more closely.


Stay up all night tonight trying to find 1 documented example of a rifle failure caused by 5.56. Then tomorrow don't try to scare people anymore


Hold on there buddy! How am I trying to scare people?
Read what I posted and tell me how that's scary. I'm agreeing with you on AR-15's, I'm pretty much certain that all of them are build tough enough to handle 5.56mm NATO loadings.

I DON'T necessarily agree with you on stuff like Savage or Remington made bolt action sporting rifles. I think that given my unfamiliarity with those types, telling someone to look closer is pretty reasonable and not 'scary'.
Link Posted: 11/2/2009 2:13:11 PM EST
As noted above the difference is the slightly longer leade in the 5.56mm.

I also agree that you would be hard pressed to ever find an AR-15 damaged by firing 5.56mm in a .223 chamber, in part because there is probably as much difference with the range of .223 and 5.56mm chambers as there is between them. If you use a new .223 reamer you will get a larger chamber than if you use a .223 reamer at the end of it's useful life and the same applies to a 5.56mm reamer or any other caliber reamer.

The other part of the no accidents caused by 5.56mm in a .223 chamber equation is that the AR-15 handles higher than SAAMI pressure fairly well with in the bounds of reason.
Link Posted: 11/2/2009 2:13:41 PM EST
Find a Remington, Savage, or something made in South America that has ever blown up. There aren't ANY.

You added the vailed warning
If your rifle was a civilian marketed sporting rifle, THEN I would consider looking into the details much more closely.


Don't feel like I'm singling you out though, I have challenged everyone for years to find an example for me and no one has yet.

Therefore I'm calling BS on the 5.56 scare.
Link Posted: 11/2/2009 2:18:09 PM EST
Originally Posted By ranchhand:
Find a Remington, Savage, or something made in South America that has ever blown up. There aren't ANY.

You added the vailed warning
If your rifle was a civilian marketed sporting rifle, THEN I would consider looking into the details much more closely.


Don't feel like I'm singling you out though, I have challenged everyone for years to find an example for me and no one has yet.

Therefore I'm calling BS on the 5.56 scare.


It may be BS..but those companies still put .223 on their rifles instead of 5.56..its just like with old 1903's...low serial number...bad to shoot...might blow up..but people still shoot them..cause "hey ive never heard of one blowing up" i still wouldnt..and i wouldnt advise someone to shoot 5.56 out of a .223 chamber even if i myself dont think its a big deal..of course i wouldnt either..
Link Posted: 11/2/2009 2:26:51 PM EST
Originally Posted By ranchhand:
You added the vailed warning
If your rifle was a civilian marketed sporting rifle, THEN I would consider looking into the details much more closely.



That 'veiled warning' is not veiled, and not a warning. It's an instruction to look into the damn details more flipping closely!

This goes right back to what I said about the AR-15's. If the bolt locks closed without having to be forced, and the chamber pressures that will be produced are within tolerance for the rifle (Guaranteed true on AR-15's), I don't see a problem.
But because I don't know the limits of every single rifle produced, I choose to instruct shooters/owners to investigate the details for their particular firearm on their own, and determine the safety from there.

This is like the .308/7.62mm in Spanish Mausers debate...
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