M1 Blows Up!

[Longcruise]

A member at my club had an M1 blow up while shooting the commonly available Korean 30-06 ammo.  So far the conclusion is that it was probably an undercharge that detonated.

Thats all I know and it's posted here FWIW.

[Airsporter]

Has this rifle been examined by a firearms expert familiar with the M1?  

In my experience, as a former high-power shooter, many M1 blow-ups are the result of slam fires.  That is, something (e.g., dirt, fouling, a metal fragment from the case or primer, etc.) jams the firing pin in the protruded firing position.  The next round fires as the bolt (with the protruding firing pin) slams the cartridge forward into the chamber, before the bolt locks.

[Longcruise]

airsporter, That could have been the cause.  I have not had a chance to talk directly to the owner/shooter of the rifle but may be able to do so at the March Service rifle match at my club.  If I can shed any more light on this, I'll bring the topic up again.

[CAV Trooper]

So far the conclusion is that it was probably an undercharge that detonated.

Since they are built to withstand greater pressure than that developed by a round with a full powder charge, there's no way an undercharged round can hurt a rifle.

What a severely undercharged round (having very little or no powder) could do is to stick the bullet in the barrel. If that happens, the next round fired will KB the rifle. As was also suggested, a slam fire (with the bolt out of battery) is also a good possibility. Glad your friend wasn't hurt.

Just out of curiosity, does the M1 in question have a receiver built by Century?

[Longcruise]

Since they are built to withstand greater pressure than that developed by a round with a full powder charge, there's no way an undercharged round can hurt a rifle

There is a known phenomenon of undercharged cases detonating.  I don't know which powders are included in the suspect list, but one example is H110 and W296.  Granted, these are not rifle powders but the detonation scenario may not be exclusive to pistol powders.  I don't know the answer.

Glad your friend wasn't hurt

I don't even know the guy.  This is from my club newsletter.  I'll be seeing the guys who examined the rifle after the fact at the next service rifle match and will question them at that time.

Just out of curiosity, does the M1 in question have a receiver built by Century?

Will aks about that too.  Didn't know Century made M1 receivers :?

[CAV Trooper]

There is a known phenomenon of undercharged cases detonating

I've been shooting for close to 50 years and hadn't heard about that. I'll have to look into it.

example is H110 and W296

I realize the guy was using Korean surplus ammo but anybody who would use pistol powder in a 30-06 reload is a moron.

Didn't know Century made M1 receivers

Unfortunately they did. Then they added surplus parts kits to make up complete rifles. The majority of their receivers were way out of mil spec and the end product rifles ran the spectrum from barely functional to down right dangerous. Nearly all well known garandsmiths refuse to work on them.

Take a look at the M1 FAQ on the Fulton Armory web site for a real eye opener on M1's built by CIA. If the rifle that KB'd was a Century, that could be the answer right there.

[Airsporter]

Actually, the free floating firing pin design in the M1 can contribute to a slam fire under certain conditions. It doesn't have to get stuck.

I heard they lightened the firing pins in the early 40's to lessen the frequency of this happening

I hope its not due to something like sensitive primers in the Korean stuff cause I bought a bunch of it!

[Longcruise]

I realize the guy was using Korean surplus ammo but anybody who would use pistol powder in a 30-06 reload is a moron.

Of course, but you seem to be missing the point in that the 110 and 296 powders are cited as examples of powders that are known to detonate in undercharges.  The point is that they are not the only powders that could detonate.  Go ask around the cast bullet forum about undercharges and detonation.

Unfortunately they did

Wonder how many laswsuits were inspired by those receivers? :eek:

[willysjeep134]

The military uses primacord as an explosive by lighting both ends, so I am told. When the two flames meet somewhere in the middle it makes the primacord detonate instead of burn. (this is just what I have heard)

What happens in a firearm, supposedly, is if the powder fills less than half the case, the primer flash shoots over the top of the powder charge and ignites both ends of the charge. When the two flame fronts meet it makes a detonation instead of just burning, which can blow up rifles.

This is all just repeated from what I heard on line at some point. I haven't researched it or anything, so it might not be true. If it is, it makes sense how an undercharged case could cause a rifle to blow.

[CAV Trooper]

The military uses primacord as an explosive by lighting both ends, so I am told. When the two flames meet somewhere in the middle it makes the primacord detonate instead of burn.

Primacord (aka detcord) is actually a plastic high explosive (PTEN, RDX or some others) that is first encased in a textile yarn and then covered by a plastic and yarn sheath for waterproofing. It only needs to be initiated at one end by a blasting cap and burns (detonates) at about 25,000 fps. I've used a bunch of it. Neat stuff and very safe. A few wraps around a tree and it's better than a chain saw. Faster and more fun too.   :-D

What happens in a firearm, supposedly, is if the powder fills less than half the case, the primer flash shoots over the top of the powder charge and ignites both ends of the charge. When the two flame fronts meet it makes a detonation instead of just burning, which can blow up rifles.

What about the fact that when reloading, there are many proper charges in which the powder doesn't come any where near to filling the case? Smokeless powder burns very rapidly and produces gas. It can't be made to detonate like a high explosive. If it could, we wouldn't be allowed to buy it.

The amount, type and burn rate of the powder determines how much gas is produced which determines the internal pressure on the chamber. IMR4895 is the standard powder in .30 caliber (30-06) military ammunition. How could a 10 grain charge possibly produce more gas (ie: pressure) than say a 25 grain charge?

I won't state for a fact that there aren't other ways, but the only things I know of that can KB a rifle are either a massive overcharge of powder (unlikely due to case capacity), the wrong powder (very possible), a plugged barrel (definitely), completely FUBAR headspace or a round firing with the bolt out of battery (both possible).

[GGaskill]

The rifle powders that have a reputation of "detonation" with low power charges are the real slow burning ones used primarily in magnum cartridges.  Stuff like 4831, 5010, 7828 maybe, 785.  They shouldn't be used for light loads period.  In an M1, even full charges of these powders shouldn't be used because they cause excessive port pressure and operate the mechanism too fast, bending or breaking the operating rod.
 
If a reload was the cause of the "blowup", I would suspect a high primer before anything else.  If there is any ammo of the lot used left, check it for high primers.

[Longcruise]

The rifle powders that have a reputation of "detonation" with low power charges are the real slow burning ones used primarily in magnum cartridges. Stuff like 4831, 5010, 7828 maybe, 785.

That's my understanding too.  In talking further with some of the cast bullet shooters it seems to be thought that even the medium speed powders can detonate in reduced charges.

If a reload was the cause of the "blowup", I would suspect a high primer before anything else.

As stated earlier, it was the korean surplus ammo that is commonly available these days.

[GGaskill]

There have been a few reports of "detonation" with medium burning rate powders in reduced loads but the analysis I have seen implies that the maximum pressure reached is substantially less than that reached with the slow burners.

The real problem with investigating this phenomenon is that it happens in uncontrolled situations with little reliable information reported and the few experiments that have been conducted have not found the extreme high pressure events that occur in the field.

For the Korean ammo situation, I would check all the ammo readily available for high primers.  I would also check to see if the cases are "full" (I know .30-06 is never loaded to capacity in military loads but you should be able to tell a case only half full by shaking.)  Since I am guessing the ammo is government surplus, I would be highly surprised if defective ammo would not be destroyed as soon as a lot was found to be defective and condemned.  For it to escape to the world market would also surprise me.  

It would be interesting to examine the remaining rifle parts.  A "not full" case is not going to be something that can be a reasonable suspect unless unfired rounds are found which are undercharged.

[Dan Chamberlain]

The phenomenon has not been duplicated on purpose.  So the jury is still out.  All investigators have to go on is the word of the people who loaded the rounds.  Some of the people are pretty believable, but everything I've read indicates that labs were not able to discern a dangerous level of pressure spike with under loaded rounds.  I developed a theory many years ago after reading about this that perhaps the primer was unseating the bullet causing it to move forward and stop just as the powder was expanding.  This might cause what might be called an obstructed bore.  I wrote to Mike Venturino about it.  Some time later, I heard the same theory offered by another writer.  It's hard to say.  But I know that the phenomenon is still just that, a phenomenon and not a proven fact.  

Cast bullet rifle shooters fire hundreds of thousands of light loads of magnum pistol powders like 2400 with powder loads of 16 grains in large rifle cases like the 06 and 8mm and .303!  I've never heard of a detonation or read of one that was reliably documented.

Dan C

[GGaskill]

I, too, believe in the "obstructed bore" explanation for this phenomenon.
 
One of the more interesting reports I have read was reported by either C. E. Harris or William C. Davis (cut me some slack here as I am writing this from memory) about a long term test at Savage.  The cartridge was .243 Win and the experiment recorded pressure readings from every shot beginning with the first shot through a new barrel on up to 300 or so.  The interesting part was that around shot number 250, there was a high pressure event with the pressure recorded in excess of 75,000 psi.  Neither case nor gun failed and the experiment continued. One other high pressure shot was encountered.  There seemed to be a correlation between pressure and bore/throat erosion.