Bought a Colt AR-15 CAR-A3, HBAR Elite and need some help! (Vanity)

Freerepublic ^ | 11/20/08 | Self

[Dead Corpse]

55k CUPS for .223 SAAMI. 62k CUPS for 5.56. LOA spec for both .223 and 5.56 are both 2.260 in every reloading manual I've seen. As noted, the difference is in bullet to land/grove engagment as the primary difference.

Got my info from Here.

So yes, a stainless bull barreled match grade .223 that could probably handle even the SAAMI safety net of 78k CUPS can handle the extra pressure from 5.56.

Now, since an AR newbie probably isn't going to be all that interested in dotting every "i" and crossing every "t" on their first purchase, a simple warning about the very real differences in pressure seemed warranted without going into 11 pages of techno-babble.

Capice?

[Dead Corpse]

Design of the barrel is everything. From how much chamber pressure it can safely hold, to the final numbers on the external ballistics, to how much heat it'll dissipate under sustained fire.

Metallurgy, machining tolerance, heat treating, etc... all are parts of it.

Again, it all comes down to how much pressure a given design can deal with. 5.56 chambered pencil barrels will have the looser tolerances. They also lack accuracy because of it. The same pencil profile in .223 match chambering would indeed come apart under sustained 5.56 diet. The same .223 chambering with better steel and a bull barrel profile can eat 5.56 all day long, even if you end up ironing a few case heads.

[RetiredNavy]

Absolutely understand your point about barrels and the differences between them. As long as the pressure vessel (chamber) portion in your bull barrel is larger than those with a “pencil” barrel your comparison may work well. As many bull barrels simply carry the chamber portion forward to the end of the barrel this comparison doesn't always hold true. Additionally, even the “pencil” barrel is only thin well past the chamber of the firearm, where pressures rapidly decrease.

You also have to consider the other parts in the equation, bolt strength, lug strength, and gas pressure in gas powered actions (AR 15 for example). Exceeding the recommended pressure in the barrel also causes increased stress on all of these components. Do it often enough and you have potential for breakage of supporting components like those mentioned.

As previously mentioned, the concern using 5.56 in a .223 chamber has nothing to do with the barrel profile, rather jamming the 5.56 in a tight .223 chamber basically means that you are shooting a proof load every time you pull the trigger. Not a good situation.

Thanks for the discussion.

[RetiredNavy]

Absolutely agree that design of the barrel is critical to safety and accuracy. Also agree that 5.56 chambers are different than a .223, having a longer leade being the main difference and causing the concern at hand.

As posted previously, a 5.56 round designed for the longer leade of the 5.56 chamber will often be jammed into the rifling of a firearm chambered for the .223, causing increases in pressures of up to 20,000 psi, making every shot a proof load.

Thanks for the discussion.

[Dead Corpse]

As previously noted, both the 5.56 round and the .223 round are exactly the same length. The tighter chamber tolerances on .223 don't lead to anything being "jammed" anywhere. You just have a decreased distance to the beginning of the rifling.

As for bull barrels, the extra material absorbs shock better. Where thinner barrels "flex" a lot, bull barrels don't. At all. It's what makes them inherently more accurate. Not having that flex prevents them from splitting ahead of the barrel nut as you see with thinner barrels shooting over-pressure loads...

Further, stainless barrels are made of... stainless steel. Arguably "tougher" metallurgically speaking than the steel used in most unlined and chrome lined barrels.

Also, the estimates I've seen for 5.56 causing an overpressure condition max out at the 15k CUPS range. Not good for your bolt face at all, but keeping an eye on what you are shooting, where you got it from, and how your rifle "eats" it can go a long way to avoiding a "kaboom".

Finally, the Winchester white box 55gr 5.56 I mentioned earlier isn't loaded to NATO 5.56 specs and is commercially available almost everywhere. At best, you'll see maybe 54k CUPS out of it. It's good for plinking and practice, but for best accuracy, handload your rounds for your rifle and shooting style.

[Lurker]

To add to the confusion one company I know of is marketing what they call the Wylde Chamber.

As if there weren't enough confusion already.

L

[RetiredNavy]

Dead,

I really don’t have a brand in this fire as I have not shot commerical or military ammo in any of my guns (.22lr excepted) for 10 years. Like you I reload and measure OAL to ensure both accuracy and safety.

The issue I have is providing partial or misleading information to newbies, which can decrease their safety significantly. As to this discussion, I, like you, have research this issue pretty extensively and try to make sure folks have as much information as possible so they can make their own decisions.

There is a lot of confusing information out there about this issue and hopefully this discussion has cleared up some of it.

One of the sites I found is Fulton Armory:

From Clint McKee of Fulton Armory (builder of high end AR-15s) - http://www.fulton-armory.com/556-vs-223-Chambers.htm

“What’s the difference between 5.56MM and .223 Remington chambers in the AR-15®-type rifle?

Would someone care to comment on shooting 5.56 mil spec ammo in a .223 SAAMI chrome lined AR? I’ve heard everything from yea to nay on other lists and am looking for the voice of reason here. I have an Armalite M15A2 on order that I was told by Armalite would have an M16 Nato chamber (I specifically asked this before I ordered). Now they say all their guns have SAAMI spec chambers but they are going to switch the chrome lined ones to Nato in the future due to customer demand. I know that SAAMI says not to shoot 5.56 in a .223 chambered gun, but Armalite says it’s fine. —Chance

---

If we are talking about .223 Remington SAAMI-spec chambers in an AR15, OH NO!

Do NOT use such a chambering if you EVER plan on shooting any military NATO 5.56 ammo, which happens to be only the most common, least expensive and most widely used AR15 cartridge available in all the world. In other words, NEVER buy/use a SAAMI-spec chamber in a battle rifle, especially if the barrel and chamber are chromed, as you cannot fix it!

Here’s the problem. Many NATO cartridges have bullets that will become jammed into the rifling of a SAAMI chambering (the throat is too short). This is VERY DANGEROUS, for a great number of reasons....(deleted info about his 5.56 match chamber)....

Hope this helps.

Best regards,

Clint McKee”

As far as barrel vibration, there is an interesting video here - http://www.youtube.com/watch?v=xxB_ZrZJQoA - that shows a M1A match rifle (usually have heavier barrels than standard issue) in slow mo. Watch the end of the barrel, it really whips around.

Not sure I believe your contention that bull barrels don’t flex at all, don’t have video evidence either way. A good test would probably be to add a vibration dampener to it somewhere and see if it changes POI.

Thanks for the discussion, I hope folks have learned a little something from ie, I have have certainly enjoyed it.

[RetiredNavy]

Lurker,

I have seen the Wylde chamber described as an attempt at a “5.56 Match” chamber. Basically an attempt to improve both .223 and 5.56 accuracy when used in the same chamber.

[Lurker]

I know my rifle is chambered for .223 but I've had no issues with Lake City Mil-Spec green tip through my Rock River.

It's the 'heavy barrel', so I'm not too concerned about the pressure differences.

I now reload using .223 dies and a 62 gr. soft point bullet for 'social' work.

L

[Lexinom]

Ho Ho Hoooo!

[smokingfrog]

C MP 5.56 NATO 1/9 HBAR = Colt Magnafluxed, in 5.56 NATO, 1 in 9 twist, with a HBAR profile

If your barrel is stamped like this you can shoot NATO 5.56 ammo.

[Spatha]

mmanager, as for quality mags, you might want to consider Magpul’s PMags...If you can find them!

Here’s a link that might give you an idea of the PMags durability.
http://www.youtube.com/watch?v=UCFXcOOb4jc

I have several and love them.

Virgil Tripp makes some very good mags as well.
Good luck!

[Jim Noble]

I'd really like to help, but in the spirit of all Americans getting along, hope, and change, I gave away all my guns.

Used to have lots in the house, but no more.

Nope.

Peace out, bro.

[mmanager]

Good luck in the coming years :)

[mmanager]

Thanks

[mamelukesabre]

all alluminum mags bend when you squeeze them. Unless you’re a sissy.

[Shooter 2.5]

Take the time to buy good quality magazines. They’re out there. You just have to keep looking. There’s no sense in buying a fifteen hundred dollar rifle and using a ten dollar magazine.

[mamelukesabre]

Mine work fine. Some are stamped “colt”, some “BFI”, some “Kay”. All aluminum 30 rounders. All can be squeezed. I think you’d have to buy steel mags to pass your squeeze test. Guess what? The military uses aluminum.

[Shooter 2.5]

I just tried my 20 and 30 round magazines and they can’t be bent with my fingers and I used enough force to be reasonable.

Yes, they are aluminum Milspec and marked Adventure Line Inc. See if you can find these magazines at a gunshow.