Exploding M-16's ????

[Tom in GA]

I was at the range a couple of dys ago shooting my Colt HBAR (1:7 twist)when one of the other shooters at the range told me that I was shooting dangerous ammo. The ammo was standard 55 grain NATO stamped ammo made in Isreal. He said that the bullet was too long for a commercial chamber and it would cause excessive pressure and ...kaboom!!! I have not seen any warnings or articles on this problem. Am I missing something?

[limazulu]

5.56 military ammo fits military chambers that are typically larger than .223 chambers. So, theoretically you could end up jamming a hot loaded military round in to the rifling of a .223 chamber which would significantly increase pressures.

Discussions of this have occurred in the past on Jouster and I don't think anybody came up with an example of that happening. But rather than guess, just take a magic marker to the bullet of one of your cartridges, chamber the round (preferrable not indoors), remove the round and see if there are any marks on the bullet. That will tell you if it's touching the rifling.

[jjroth]

is it 5.56 or.223.
Colt Hbars are NORMALLY the NATO (MilSpec) chamber.

If .223 then chambered per SAAMI specs.

Contact Colt with SN and confirm chambering.

[Jim K]

The bullet has to be forced into the rifling in any event, and there is no significant pressure difference whether there is a long leade or none. In fact, most match barrels are made with a short or no leade so as to minimize the "skid" when the bullet hits the rifling. Bullet skid can cause inaccuracy.

The amount of leade is usually determined by the ogive of the bullet(s) to be fired in that barrel, not out of concern for pressure.

Jim

[Tom in GA]

The Colt HBAR in question is marked .223 and was purchased new in 1990.

[KarlKW]

I think that your shooting colleague was trying to warn you that Israeli 5.56 x 45 mm has a reputation for being loaded "hot." The only split case that I have ever shot was an Israeli round. You may never have a problem with it, but I did. HTH, Karl

[Col. Colt]

As a Colt Armorer, I have never heard of a Factory Colt HBAR shipped with a .223 commercial chamber. If Colt ever did use a commercial .223 chamber, it would have been long ago, in the very beginning - although I do not believe they did. The reciever marking may have been an attempt to "Commercialize" a controversial "Assault Weapon" and make it seem "less military". On the top of the barrel in front of the front sight should be a stamping with the military designation - 5.56, C (chrome) and MP (proofed and Magnetic Particle inspected) and 1/7 (twist) - in which case it is totally safe to shoot with any NATO spec 5.56 Military round. I would assume that the Israelis would adhere to that spec, and what the commentator saw was a bright muzzle flash and sharp report from a real, full power 5.56 NATO load. Most US commercial is a little light.

Colt's chambers have long been MilSpec, and they did not offer a "Commercial chamber" as did some of the clones. You could ask over on AR-15.com if anyone there knows of an exception. How is your barrel marked?

And the only way I know to "explode" a Colt AR is to leave out the bolt cam pin on assembly (DON'T!!!!!) or plug the bore.

[drshame]

I had a squib round unknowingly block the bore of a Colt USGI A-1 upper.
The next round blew out the bottom of the magazine from the back pressure.
Got my attention.
The barrel's fine and still shoots great with no apparent ill effect..
It was a testament to a very good design and my need to greatly improve my reloading.
AR's don't blow up unless idiots don't pay attention to what it's being fed.

[Brad in Idaho]

On the top of the barrel in front of the front sight should be a stamping with the military designation - 5.56, C (chrome) and MP (proofed and Magnetic Particle inspected) and 1/7 (twist) - in which case it is totally safe to shoot with any NATO spec 5.56 Military round.

Colt's chambers have long been MilSpec, and they did not offer a "Commercial chamber" as did some of the clones. You could ask over on AR-15.com if anyone there knows of an exception. How is your barrel marked?


My Colt H-BAR is marked as you describe except it is 1/9 twist. My question is, when you reload for a 5.56 chambered rifle, should the overall length of the finished cartridge be longer than for a commercial chambered .223?

Sorry if it's a dumb question, I'm a novice at handloading.
I'm getting components and tools together to start reloading for my H-BAR and I want to get it right.

[Col. Colt]

Brad, there are no dumb questions - it's only dumb when you fail to ask and get yourself in trouble due to pride!

Many Match handloaders tailor there accuracy loads to the individual chamber by seating the bullet to the "most accurate" length. You would want to be pretty advanced in your handloading knowledge and practice before you attempt this, and special tooling is recommended.

I suggest you read up on the subject extensively and talk to some advanced loaders, but until you feel competent, stick with the specs in the Handloading Manuals. (Also, an AR has a maximum length due to the magazine itself to consider.) Get ahold of Zeddiker's (sp?) book "The Competitive AR15" and give it a read - it will explain. Cheers, CC.

[DaveE]

I also have an old Colt SP-1 in the 57K serial number range. I have owned this rifle for quite a few years and never fired it. On the side it says .223 and the barrel is only marked C MP Chrome bore. I was always told the at the SP-1s were really .556 no matter what it said on the side of the rifle. I now have the urge to fire it but not sure what caliber ammo to buy. My local gun shop has 400 round cases of .556 for less than $200 which seems ok in today's market. I just want to make sure i am getting the correct fodder for the rifle. Thoughts?

Dave

[Col. Colt]

Dave,
Colt produced the SP1 right alongside the M16 - the parts (except for the full auto fire control group) were the same. Colt once did an ad joking as to how their inspectors had to look closely to tell the differance in the factory!

Your barrel is marked the same - and is the same, as an M16 from the same era - and has a 5.56MM chamber. Go to AR15.com and read in their Retro forum about SP1s. Cheers. CC

[DaveE]

Dave,
Colt produced the SP1 right alongside the M16 - the parts (except for the full auto fire control group) were the same. Colt once did an ad joking as to how their inspectors had to look closely to tell the differance in the factory!

Your barrel is marked the same - and is the same, as an M16 from the same era - and has a 5.56MM chamber. Go to AR15.com and read in their Retro forum about SP1s. Cheers. CC


Thanks much, I appreciate the info.

Dave

[bblake]

most Colt 7 twist barrels had overly long chambers. You can purchase a gage to measure throat length that aids in seating your bullets to a given length short of or into the lands and grooves of the barrel. It isn't uncommon to have a throat so long on a colt barrel that an 80 grain sierra bullet seated out to a few thousandths off the lands barely has enough neck tension to hold the bullet. Most of the 7 twist colt barrels shoot well, and more than one person has made master or high master with them, that being said, the throat was a weak point.

Brig Blake

[edlmann]

The Colt HBAR in question is marked .223 and was purchased new in 1990.

Colt has been somewhat inconsistent about this. Is the .223 marking on the lower receiver or on the underside of the barrel? THe barrel marking is more important.

FWIW; AFAIK; IMHO; YMMV; yadda, yadda, yadda.

Regards, Ed Mann (edlmann@embarqmail.com)

Bobby Bowden is doing a fine job - just leave him alone.

Albert says, "Click here (http://www.ufalumni.ufl.edu/gatorspirit/wallpaper) for free Gator wallpaper."

http://i192.photobucket.com/albums/z111/edlmann/FlaGators2.png

[Jim K]

I have heard that using GI ammo in a "civilian" rifle will blow up the gun. I have also heard that using civilian .223 ammo in a GI spec rifle will cause the rifle to explode like an A-bomb, complete with mushroom cloud. I have even heard that using GI 5.56 ammo in a .223 Remington 700 will destroy it - one of the strongest rifles ever made!

Now one would think that rifles blowing up right and left from using the "wrong" ammo might have come to the notice of the various gun and ammo manufacturers, and suitable warnings issued. Since I have seen neither blown up guns nor any warnings about nuclear bomb ammo, I tend to think the whole thing is nonsense, fed by ignorance and misunderstanding. (Note, I didn't say that all 5.56/.223 ammo will be accurate or even function perfectly in all guns of the caliber; I am addressing the "guns blowing up" issue, not accuracy.)

Jim

[limazulu]

I have heard that using GI ammo in a "civilian" rifle will blow up the gun. I have also heard that using civilian .223 ammo in a GI spec rifle will cause the rifle to explode like an A-bomb, complete with mushroom cloud. I have even heard that using GI 5.56 ammo in a .223 Remington 700 will destroy it - one of the strongest rifles ever made!

Now one would think that rifles blowing up right and left from using the "wrong" ammo might have come to the notice of the various gun and ammo manufacturers, and suitable warnings issued. Since I have seen neither blown up guns nor any warnings about nuclear bomb ammo, I tend to think the whole thing is nonsense, fed by ignorance and misunderstanding.
Jim

I'm beginning to wonder about this myself. :dunno: Even tight chambers have to accept ammo that fits the magazine so if your ammo is no longer than magazine length there shouldn't be any problem from that. The bullets are the same diameter so the only problem would be in case headspace and possible slamfires. :runaway:

[ClaudeH]

I'm no expert at all, but I am at least a thoughtful sort. ;) I believe the differences between the chamber specs and loading specs for .223 and 5.56 are way overblown. Real, but overblown. Yes, the pressure spec for 5.56 is nominally higher and the chamber is nominally larger, but I really believe the differences are moot in modern firearms. The breeching of an AR-type rifle or a Model 700 is more than adequate for anything marked 5.56.

I think you should be a little more cautious if you have a firearm of more marginal design strength such as a break-action Savage M24 or a some old one-lug bolt action rifle, so you can't dismiss the differences entirely. But it sure seems to be an overblown issue in regard to AR-type rifles and modern bolt actions.

[Col. Colt]

Guys, I think that there can be a problem, but that it does not usually involve blown up rifles. Claude, you right about the action strength of most designs. But - if you use a "Match" tight .223 chamber with "long throated and hot" 5.56MM GI round you can "pop a primer", letting gas flow back at you and possibly cause some erosion at the firing pin hole. I believe the book, "The Competitive AR-15" by Zeddiker Publishing covers this pretty well.

In the original questions, the worry was about whether a Colt AR marked .223 had a .223 chamber or a 5.56MM chamber. To my knowledge, all standard Colt ARs have the more generous 5.56MM NATO chambers/throat length, regardless of markings. (They did make a few in .222 for export to "No Military Cartridges allowed" countries.) Other makers, I believe, offered a choice of chambers, for those that wanted "tight" Match chambers for the last little bit of accuracy.

So I agree that strength is not a problem - but high pressure can still cause troubles and/or blow hot gas in your face - not a safe or pleasant experience! And so I would want to know which chamber I had, and load accordingly. But "Exploding ARs?" - Not Likely. CC

[Jim K]

I well remember the hoopla and hype when the .223 and the AR-15 were first marketed. Colt bought the rights from Armalite, and launched a high intensity campaign to sell the general public on the gun, so they would pressure the mililtary to buy it. Among the claims for the little round were that a hit anywhere on the body meant instant death; that the bullet would penetrate helmets at 1000 yards, and 1" armor plate at 500; that the shock of a bullet passing close to an enemy soldier would incapacitate him, and on and on. All nonsense, of course.

At one of the NRA conventions, a Colt rep gave me the sales pitch. I told him I would indeed like to try out the cartridge but didn't have a .223 caliber rifle. I said that if I could get hold of some FMJ bullets, I would load my .22-250 down to .223 velocity and experiment. The guy went berserk! "Load DOWN!?" he screamed. "This is the most powerful cartridge in the world, the most powerful round ever developed!" I replied that it looked to me like a medium power varmint cartridge (which it is) and that a .30-'06 made it look pretty sick all around. He almost ran away, presumably to report my heresy to his bosses. I didn't encounter him again.

In fact, the only reason for the existence of the 5.56mm and the M16 is that the combination is reasonably controllable in full auto fire, which is not true of most full power rifles; the M14 is about uncontrollable, the FAL better, and most other guns hopeless. (The AK-47 is not really full power.)

Jim

[irishsteve]

I was looking at one of Patrick Sweeneys AR15 books,and it said that all chrome bores are 5.56 chambered so If you have a C stamped on your barrel you should be good to go with mil spec ammo.

[gew98]

Most of all of this sounds like bunk to me. I fired up oodles of M16's while in uniform , mini14's ( yuk ) and wads of other223/5.56 rifles. The only ammo problem I encountered was the A2 rifling twist (1-7) did not stabilize the M193 bullet and the A1's (1-12) did not like the M855 bullet. And for that matter I don't care for the "product improved" M855 bullet either. I see a 1-9 twist AR and I still think of it as "compromise twist".
The only AR blowup I have seen was an H&K video on how they could submerge their 416 piston upper in water pull it out and immeadiately shoot it. While they did the same thing with a standard A2 and it literally blew the upper into scrap - big pieces lost there !.

[Col. Colt]

gew98,
It's not bunk because some AR makers (not Colt) have offered "Match" barrels with the tighter, .223 Commercial "Bolt Action" spec chamber - having a much shorter throat than military spec. If you take a 5.56MM round, loaded to max pressure and with the bullet set out to the proper length for a military throat and chamber it in a .223 Commercial chambered rifle, the bullet may be forced into the rifling upon chambering, creating much higher than normal pressures. With the .223/5.56 cartridge, the result is sometimes a blown or pierced primer and gas released into the shooters face - not good for either the gun or the shooter! The specs are not quite the same, period. The good news is that the military 5.56MM chamber is in the vast majority of ARs - and it works with both ammo types just fine. But there is always the exception...... CC.

[limazulu]

gew98,
It's not bunk because some AR makers (not Colt) have offered "Match" barrels with the tighter, .223 Commercial "Bolt Action" spec chamber - having a much shorter throat than military spec. If you take a 5.56MM round, loaded to max pressure and with the bullet set out to the proper length for a military throat and chamber it in a .223 Commercial chambered rifle, the bullet may be forced into the rifling upon chambering, creating much higher than normal pressures. With the .223/5.56 cartridge, the result is sometimes a blown or pierced primer and gas released into the shooters face - not good for either the gun or the shooter! The specs are not quite the same, period. The good news is that the military 5.56MM chamber is in the vast majority of ARs - and it works with both ammo types just fine. But there is always the exception...... CC.

The more I read these posts the more I question them. The magazines are the same for the .223 commercial and the 5.56 cartridge so if it fits the magazine then how can it get jammed into the rifling? The tighter cut chambers still won't cause a round to go into the rifling if the cartridge is magazine length.

I thought the problem had more to do with headspace issues and the potential for slam fires.

[Col. Colt]

Throat length, guys. Period. And the mag has lots of room and has nothing to do with it - we are talking in a few thousanths of an inch making a major difference in pressure. Hugo has another post regarding Olympic arms ARs on this board with a diagram that shows the difference in the throats. It isn't the "chamber", it's the distance between the bullet and the rifling created by the relationship of the loaded round and the throat, the angle of approach, etc. And it Matters! As an LE AR Armorer and a former Service Rifle shooter, trust me on this. Or read about it in Zedeker's "The Competitive AR-15".

[AKA Hugh Uno]

actually tends to mean a more GENEROUS length (to ensure the feeding of 69+ grain bullets). Usually this is a Wylde chamber or variant. Again, I doubt that ANY major manufacturer of AR rifles has ever shipped one out that has a true 1960's era bolt gun SAAMI chamber. In fact, the bolt guns made post 1970's also tend to have longer chambers also. All have decent amounts of freebore and very shallow leade angles (i.e. 1 degree vs. 3 degrees).

Frankly, I don't even think it is POSSIBLE to "blow up" (or even get pressure problems/warnings) with ANY commercially made AR rifle from a "name" manufacturer. This INCLUDES so-called "match" chambers as this virtually always means a LONGER throat and shallower leade angle.

Bushmasters "match" chamber is 1 degree, 30 minutes and allows OAL of from 2.450+ compared to SAAMI OAL of 2.250-2.30. Bottom line, if the GI or commerciaL round GOES IN, SHOOT IT.

[lyman1903]

Brad, there are no dumb questions - it's only dumb when you fail to ask and get yourself in trouble due to pride!

Many Match handloaders tailor there accuracy loads to the individual chamber by seating the bullet to the "most accurate" length. You would want to be pretty advanced in your handloading knowledge and practice before you attempt this, and special tooling is recommended.

I suggest you read up on the subject extensively and talk to some advanced loaders, but until you feel competent, stick with the specs in the Handloading Manuals. (Also, an AR has a maximum length due to the magazine itself to consider.) Get ahold of Zeddiker's (sp?) book "The Competitive AR15" and give it a read - it will explain. Cheers, CC.


+1 on Zediker's books, both the AR15 (the mouse that roared) and his match handloading book are , IMHO, must reads,

try zediker.com for info, and he has some good articles there too,

[Jim K]

So a bullet pushed into or against the rifling before firing will cause a gun to blow up? So thousands of competive shooters with other rifles have their barrels chambered and/or the bullets set out to do just that. (A long leade will allow the bullet to skid when it takes the rifling, affecting accuracy.)

But the AR-15 is different? What works for other rifles causes an AR-15 to blow up in a mushroom cloud?

At the pressures involved, a normal bullet acts like silly putty; it will move into the rifling with no problem. The only thing that can raise pressures would be too tight a chamber neck that would not allow the bullet to release properly. And that should not differ between commercial and military ammo.

I think some "experts" are off the track.

Jim

[gew98]

I have to agree Jim. A buddy I knew in the peoples republik of new jerky used to do benchrest . He called it "soft loading". That is he would seat his bullets out further and not crimp. When the round was chambered the bullet would meet the rifling and get slightly set in it and the rest would be pushed back in the case as the bolt closed home. It does cause a bit of a pressure bump , but nothing alarming. I have seen overlength rifle brass with crimped bullets that were more dangerous than softloading by far when chambered tight for obvious reasons. If someone is too lazy or casual to be bothered by trimming their brass to length they deserve what they get.

[AKA Hugh Uno]

between the barrel, barrel nut, and extension, plus the locking lugs on the bolt, it can handle any normal pressure with ease.