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AR goes Ka-Boom

3K views 29 replies 17 participants last post by  roundball 
#1 ·
I was at the shooting range yesterday and the guy two tables over was shooting an AR in 5.56 he just finished building. He had a chronograph set up and was shooting reloads out to 50 yards. The loads were 55gr, FMJ over light to mid range H335 with new Winchester brass and Winchester small rifle primers.

I've known the guy for a couple of years and he has been reloading for about ten years and is very meticulous. He keeps records of every shot he fires. The gun was a high end AR I don't remember all the parts he told me about except the barrel was a White Oak, it had a Timney trigger, and a high end red dot sight. His routine was to fire one shot, record the velocity, and mark the impact point of the bullet on a sketch. He had the powder weight marked on each piece of brass and I think he started out at 24.5gr and went to 26.5gr.

He shot about ten rounds and the last one literally blew the rifle apart. One side of the lower was gone, the barrel was cracked, and the magazine was in a dozen pieces. He was lucky because carrier was split but the bolt stayed in place. He was not hurt very bad but had a couple of cuts on one arm and a nick on his cheek.

The chrono recorded a velocity of 1,150 fps for the last shot. The one before that showed 3,166 fps. I've loaded .223 with H335 and the case would not hold a double charge without spilling out. Since the shot before the ka-boom registered a normal velocity a squib load causing a plugged barrel did not seem likely.

There were three other guys shooting at the time and all are long time shooters, reloaders, and a couple had built more than one AR. The only thing we could think of was a head space issue with the bolt, but there is no way to know for certain.

We will never know the real cause, but it sure got everyone's attention.
 
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#4 ·
yikes!

and if the chrone was recording speeds for each shot, then you know a projectile was leaving, and if he was recording impact marks, that's a double check.

if you hear any more or have pictures, post them.


was he feeding 1 at a time or a full magazine?

if full mag, were all other cartridges accounted for?

any possibility of a feed and then another round fed on top causing a primer ignition?
 
#5 ·
I've known the guy for a couple of years and he has been reloading for about ten years and is very meticulous. He keeps records of every shot he fires. The gun was a high end AR I don't remember all the parts he told me about except the barrel was a White Oak, it had a Timney trigger, and a high end red dot sight. His routine was to fire one shot, record the velocity, and mark the impact point of the bullet on a sketch. He had the powder weight marked on each piece of brass and I think he started out at 24.5gr and went to 26.5gr.

He shot about ten rounds and the last one literally blew the rifle apart. One side of the lower was gone, the barrel was cracked, and the magazine was in a dozen pieces. He was lucky because carrier was split but the bolt stayed in place. He was not hurt very bad but had a couple of cuts on one arm and a nick on his cheek.

The chrono recorded a velocity of 1,150 fps for the last shot. The one before that showed 3,166 fps. I've loaded .223 with H335 and the case would not hold a double charge without spilling out. Since the shot before the ka-boom registered a normal velocity a squib load causing a plugged barrel did not seem likely.

There were three other guys shooting at the time and all are long time shooters, reloaders, and a couple had built more than one AR. The only thing we could think of was a head space issue with the bolt, but there is no way to know for certain.

We will never know the real cause, but it sure got everyone's attention.
It could be a head space issue, but I will go with a pressure issue (aka over charge). Here's why I say this. I have burned over 60lbs of H335 over the last few years. I worked up loads for all six of my ARs, and my wife, and kids ARs. I started showing pressure signs using 25.3gr of H335 under 55gr bullets with primers starting to flow, and pretty good bolt face marks on the heads. My go to load is 24.8 gr under 55gr FMJ BT. I can, and have loaded 25gr, but accuracy was no better, and it's harser on my brass.

Here's Hodgdon's data. He was 1.2gr over charged on his max load.





 
#6 · (Edited)
I'm confused on a few levels - and I'd very much like to see if more comes out of this situation so I can learn.

* hodgdonreloading.com doesn't have a 55gr FMJ bullet. Why?
* My Speer reloading manual has min/max H335 loads for 55gr FMJ as 24gr/26gr. (This load is with a magnum primer.)
* Should I expect hodgdonreloading.com to have the same data as the Speer manual?

What a bummer of a story! I'm glad the guy is OK.
 
#8 ·
I'm confused on a few levels - and I'd very much like to see if more comes out of this situation so I can learn.

* hodgdonreloading.com doesn't have a 55gr FMJ bullet. Why?
* My Speer reloading manual has min/max H335 loads for 55gr FMJ as 24gr/26gr. (This load is with a magnum primer.)
* Should I expect hodgdonreloading.com to have the same data as the Speer manual?

What a bummer of a story! I'm glad the guy is OK.
As to expecting one to have the same data as another, no. It will depend on several things, one being what type of barrel they performed the test in.
For example, I have a bunch of Remington 55 gr bullets. Nobody has data for these so I search my manuals and find something clse in profile and the same weight. I'll use that data but start at the minimum and work up. There's just no way that they could test every bullet/powder combination out there.
 
#7 ·
i don't have a manual in front of me, however will comment that when relaoding i usually browse 3-5+ manuals, and it's not uncommon to see a max listed a gran higher than another.

look at older manuals and see higher loads than today too.
 
#9 ·
My pet load for 55gr in .223 using IMR 8208XBR is .2 over their max charge, but I worked it up from 23grs to 25.5 and have absolutely no signs of primer flattening or any other signs of overpressure, my velocity is around 200FPS less than their listing (16" barrel versus their 24" I presume.) and the brass isn't stretching much as one would think at an over-max load. I've seen a lot of people say that many of the manufacturers purposely post lower then actual max charges for liability purposes.
 
#10 ·
Years ago I developed a load for my Browning A-Bolt in 223 that showed no signs of high pressure and was not above the max loads listed at the time. I used that same load in a Thompson Contender 14 inch barrel also with no signs of pressure. It was a H335 load. H335 is one of my stocked powders that is always one of the powders I test when developing almost any new load for almost any common caliber.

When I shot that successful load through my Browning 1885 single shot I got signs of excess pressure and had to back the load down significantly.

The point: Rifles vary and effect pressures, and stay away from max loads. There is almost always a lesser load that will shoot as well.

As for this kaboom AR story: We don't know all the facts and may never know them. Was it sloppy reloading, wrong powder, gun malfunction (??), or ????. Was the ammo not crimped and the bullet had been seated too far by recoil? This can not be typical of AR's as this is the first of such stories I have heard like this, after millions of these guns have been fielded by the military and sold commercial for nearly 50 years. Someone made a mistake along the way that we will never uncover because of the destruction of the evidence. The shooter may even be hiding his mistake to avoid the embarrassment. Loosing a $1000+ gun and getting hurt as well is an embarrassment and adding a personal failure to it all can be humiliating.

LDBennett
 
#14 ·
I have hesitated to say anything because I haven't been able to relocate my sources. Just a few days ago I read in an FAQ that this one particular company generated load data using a minimum spec chamber and barrel bore so as to create the highest pressures possible while still being within SAAMI spec, ensuring that your firearm will run at the same or lower pressure. I've also read elsewhere that older methods of pressure measurement were not as reliable and missed short duration pressure spikes. As a result some loads have been adjusted to bring them within pressure limits.

Maybe it is about liability, but if either of the above two reasons is true then it is prudence regarding a very exacting and detail oriented hobby. When I compare loads from my Hornady 4th to 9th edition manual I don't see an across the board equal percentage reduction of maximum loads. In fact, in the 150gr 30-06 load data four powders (IMR 4064, Win 760, IMR 4350, and H350) have a higher max in 9th edition and only one (H414) has a lower max.
 
#15 ·
Might be kind of a 'goofy' question, but with all of the different max-loads published for the same bullet wieght, and this being a new build rifle, could it be that the rifle's chambering was .223 Remington and not 5.56mm NATO, or that the new barrel had a defect? I suspect the problem was with the rifle and not the load. The higher-than normal 2nd to last shot velocity and the very low velocity for the last shot seems to indicate that something was 'letting go' in the rifle.
 
#16 ·
SteveM:

The "Crusher" method of pressure measurement worked like this:

There was a hole in the pressure barrel with a short length of round copper inserted and captivated. The pressure would collapse the the copper. Each one cam with a calibrating table that related "Copper Units of Pressure" or CUP's to the amount the copper was crushed. So it measured the peak pressure and nothing else.

Today "Pressure Transducer" method of pressure measurement works like this:

The transducer is attached to the barrel. When the cartridge is fired the output of the transducer goes to a capture device like a storage oscilloscope or a computer that can measure the voltage out of the transducer against time. The transducer comes with a calibration table that relates voltage out to "pounds per square inch" or PSI. Along with a more accurate measure, you get to see the peaks and valley of the pressure curve including spikes in the pressure if there are any. CUP's and PSI are not directly convertible to each other. So only compare CUP's to CUP's and PSI to PSI in the reloading manuals.

Some loads developed before PSI measurements were found to be dangerous and manuals reflect that by a reduction in pressures allowed. It was not an across the board reduction in all loads.

LDBennett
 
#18 ·
some people endlessly chase fps. I'm not one of those. Vi agree with your reasoning, if you are operating in the upper 5% of your capability to get what you need done, it may be time to step up to a different cartridge or platform.

I can shoot flies on a 199yrd target with my 218 bee bolt gun all day, but if I had to take medium game with it, I'd be depending solely on perfect shot placement. Stepping up to a 223 for instance would give me lerway in case I missed the eyeball, etc
 
#19 ·
I test loads in one grain intervals from minimum to max. More often than not the max load never turns out to be the most accurate. I may not even shoot the pre-loaded max load if I see anything that indicates too much pressure in lesser loads. My reloading generally is about accuracy, not max velocity. Chasing velocity is dangerous and usually not beneficial.

LDBennett
 
#24 ·
oldgunfan said:

"a half charge??"

I think not. The pressure is generated when the cartridge is confined by the chamber and the gun. If the gun was coming apart as reported the cartridge never would be able to generate full pressure to give full velocity. It may have been a partial charge but the low velocity is not enough evidence of that.

It might have been a slam fire where the cartridge was not all into the chamber. But for the whole of the gun to come apart says excessive pressure for a reloading error to me. But I am only guessing. This was a new gun, as I understand it, made by the owner. Did he make a mistake in the build?? Was there a bad new part? Was the headspace correct? Again, we'll probably never know for sure.

LDBennett
 
#25 ·
Some years ago I was shooting a Ruger Mini-14.I had a full mag and was shooting away and about half way through the magazine I heard a strange sounding, Whoooop noise.A bullet was stuck half way down the barrel and I stopped before firing off another round.I had to pound it through with a cleaning rod.Thank God I stopped in time,it could have turned out badly!It must have had little powder or just a primer only,I'm not sure.Do you think a primer would be strong enough to push a .223 bullet half way down the barrel?
 
#27 ·
A primer only case will propel the bullet into the barrel where it will stick. The lack of a normal loud noise is the evidence that the powder was missing or did not ignite. I have had it happen to me when the primer hole in the case was blocked by tumbler media mixed with liquid case polish.

LDBennett
 
#28 ·
There is no mention in the original post of case condition, the last fired round and the failure round should have told more of the story. I do not reload, and while we can all guess till the end of days there is the clue of the condition of the brass that is missing.
Also, what bullet was used? Full jacket or what, could the bullet fail or separate in the barrel or did a case neck fail and lodge in the bore? Guessing, but no opinion; at least the shooter was not seriously harmed.
 
#30 ·
I'll share a personal experience concerning overloads-not related to the AR. I was shooting a S&W 38 Special revolver with handloaded rounds using Unique and 158 gr. SWC bullets. One report was extra loud and found the cylinder bulged. Had the gun repaired by having cylinder replaced. Finally decided the operator error, me, may have been the powder measure still had a partial charge of a faster burning powder making for a dangerous duplex load that damaged the revolver. Glad the AR shooter was not seriously injured. May be helpful to see if the locking lugs had sheared or the lug seats in the barrel were damaged.
 
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