High Pressure Event

[Pirate69]

It appears that I experienced a high pressure event with a Garand and I am having difficulty understanding what occurred.

A clip was being fired when lots of smoke came out of the action. Round was number six of the eight round clip. I retracted the bolt to inspect and found the case was stuck to the bolt face. The extractor had been pushed back by flowing brass as well as the ejector. A perfect mold of the extractor and ejector hole was formed by the flowing brass on the case head. The primer had also been blown out of the primer pocket. The brass that flowed into the ejector hole formed a peg which maintained the case attached to the bolt face. I measured to brass flow, from the case head, into the ejector and extractor area and it measured approximately 0.038”. Two nice little bumps on the case head.

The prepared rounds consisted of:
Boolit: 212 grain power coated and GC boolit sized 0.311” to 0.312”. Boolit is seated just deep enough that a clip can be inserted into the receiver. GC is at the very bottom of the neck.

Powder: 32.5 grains of IMR 4895 pulldown.

Case: military surplus. Cannot read stamping since it was pressed out during event.

Rounds preparation:
Small number, 20, were loaded to test a load. Cases were staged in a loading block. Powder was dropped by a calibrated RCBS powder scale and individually poured into the cases. After powder dropped, Q-tip with tape flag used to verify that powder was in each case and same level. At this point a 0.7-1.0 grain square of Dacron filler was added. An issue should have been detected during these steps. And, I have verified that a double charge will not fit in a 30-06 case to begin with. I think I can rule out a double charge.

Possible causes
GC came off the boolit and remained in the barrel. Could have happened but do not think that this could result in a pressure build-up of this magnitude.

Boolit pushed into the case during recoil. Not sure how this would affect the pressure. Seems that this would allow gases to vent more freely and lessen pressure.

I cannot say that I noticed any difference in recoil from this round and the round before it. The action had worked properly and eject the prior case. Squib load can be ruled out; I think. Noticed problem only because of the smoke from the action.


The rifle did not suffer any damage and I continue to shoot it without any indications of any problems. Operating rod appears okay. Vented gas plug may have helped. No stock damage, no bolt damage, no receiver damage. As stated earlier, I do not understand what happened. Anyone have any insights?

[Pirate69]

The 32.5 grains of IMR4895 is the minimum amount that will work the action. The Dacron helps to hold the powder against the primer. Some people choose to use a filler at these reduced load levels and others do not. The filler only adds approximately 1 grain to the projectile load.

why was the Dacron filler needed?

[Larry Gibson]

Pirate69

I suspect, given the excellent detailed explanation you've provided, what occurred was a near SSE. With normal loads of 4895 in an 06 case such as you used fired single shot or even fed from the magazine of a bolt action the .7 - .10 gr Dacron filler is quite sufficient. However, given the fact that it just barely may actually "fill" the airspace, the Dacron filler of rounds still in the magazine can get jarred around by the recoil and slamming of the action back and forward. The powder can migrate around and into the filler. This can cause a "hang fire" which may not even be noticeable causing the bullet to briefly stick in the leade. That can really raise pressure before the bullet gets moving again. In your case the heavy PC'd bullet may have caused it to stick in the leade easier.

I suggest you change to a 1 - 1.5 gr Dacron filler for use in the M1 to ensure it is actually a "filler" that, under the recoil impulse of the M1, will cause it to actually hold the powder in place.

[runfiverun]

too little Dacron could have allowed everything to shift forward and compact at the front of the case.

the other thing that could have happened was you got a soft headed [over annealed] case.

[dubber123]

How is that a reduced load though?

And some forums seem to think, after a quick google search of 4227 and m1 garand, that the powder is not safe for a garand.

Did I miss something? He is not using 4227

[Kestrel4k]

[...] Case: military surplus. Cannot read stamping since it was pressed out during event.

Would perhaps be good to keep records ID'ing the cases used for the loading; certainly assists the forensics on a destroyed case.

I've seen a typical number of examples of case failures (all from others or online, fortunately); the headstamp info could always be read relatively easily.
To remove the headstamp entirely - that brass sounds way too soft to me.

A defective case could be more probable if it was foreign-mfg; Korean 'PS' is the first that comes to mind.
But even a defective USGI case is a possibility (and were most likely connected to the 'low-number' '03 situation, for example).
** Were these cases fired by you before, or did they come to you from less-known sources ?

Since milsurp '06 brass is plentiful & inexpensive, it is relatively straightforward to segregate cases for batch loading - even LC vs HXP vs xx.
Accumulating a sufficient supply of trusted cases makes it relatively straightforward to surplus/dispose the misc headstamps, which is what I've done.

[earlmck]

I'm with Kestrel4k on this -- defective (waaay too soft) brass. To do that kind of damage to a proper case would take -- I don't know, but probably 150k psi? Which would have caused some real rifle damage. And I also have seen some high-pressure events that caused something similar to the case heads and have never seen the headstamp "ironed out". That also would seem to suggest very soft brass.

But if these were once-fired (or several-fired) cases that would eliminate the "very soft brass" theory and Mr. Kestrel and I will have to return to the drawing board.

[Wayne Smith]

One other possible issue. Loading some mixed military brass I noticed that some had less neck tension than others, probably thinner brass. Less neck tension means a boolit could slip back in the case under recoil. I have no idea if this would cause that much damage, though.

[Pirate69]

This case had 3-4 reloads on it.

[Pirate69]

With the help of a magnifying glass, I may have identified the case. I can see a W (270 degrees and a T (0 degrees) at 90 degrees to each other. Found a similar case with four marks at 90 degrees. They are W, 3, 5, T. Starting with the W at 0 degrees and progressing each mark by 90 degrees. Could be the same case.

[tomme boy]

Sure the bolt was fully in battery? Could have fired with the bolt not entirely locked????

Larry would be the person that can say whether that can happen or not on a Garand.

[samari46]

Sounds like twin cities 53 or TW53 for the headstamp. Many years ago was given a sealed tin can of TW44 ap ammo all 520 rounds of it. Pulled the bullets averaged the powder weight, reprimed with non corrosive primer and shot a lot of it. Still have about 40 primed cases. Frank

[Hick]

You said the boolits were just seated enough for the clip to go in the garand. Could it have been that the case was overlength? If the case was too long the lip of the neck can hit the shoulder in the chamber. This puts a very tight crimp on the boolit which prevents its release until the pressure goes waaay up. The max 30-06 case is something like 2.494 (don't have the book n front of me). In my Garand a case of 2.510 hits the shoulder in the chamber and locks up the bullet (I have to watch case growth).

[Pirate69]

This case was one of a batch of mixed cases that was trimmed to minimum length before starting round development. 3-4 reloads since trimming.

[Larry Gibson]

Sure the bolt was fully in battery? Could have fired with the bolt not entirely locked????

Larry would be the person that can say whether that can happen or not on a Garand.

If the M1 Garand is within spec it will not fire out of battery.

However, the OPs example is definitely a high pressure event. Any rifle firing out of battery is not a high pressure event. Yes damage to the rifle can occur but you will not see brass flowing as in this example.

[tomme boy]

Thats what I figured Larry. I was thinking out loud. I was thinking that the brass might have been slammed back against the bolthead like if it was bad headspace.

I find lots of 308 win brass with ejector hole swipes and impressions all the time. Yet the ammo is perfectly safe in a bolt gun and no swipes or impressions. Too high of port pressure.

So I am guessing that the port pressure was low enough to not damage the op rod? With the gas port being where it is on the Garand the spike had time to go down before the bullet passed the port.

I can definitely see the action causing enough force to migrate the powder with the amount of Dacron he was using. I was using 1-1.3grs of dacron in my 308 as I did not want this to happen.

Pirate69 I am really glad you did not hurt the gun! I would be ditching all this MIL brass and get some newer commercial. One less thing to worry about. I have run into lots of military brass that has some age on them. And they all seem to be harder than newer brass.

[runfiverun]

the odd thing is the case getting all jacked up but not enough op-rod pressure to bend it.
high pressure is usually high pressure everywhere.

I'm kind of thinking the boolit got shoved back in the case then had to fight it's way back out.

[vzerone]

Art Tuttle was the "Main Troubleshooter" for manufacturing M1 Garands at Springfield Arsenal during WWII. Mr. Garand wrote that he had designed the M1 and then had to redesign it for mass production. Art Tuttle was the "Go to Guy" who figured out a lot of the problems and solutions on mass producing the Garand. Mr. Tuttle passed on a lot of insight and experiences he ran into and they were published in the early years of the Garand Collectors Association Journal. I can not begin to tell you how fortunate that was. OK, now that I have "set the stage," then on to Ted Brown's quote.

"Mr. Tuttle also held that the receiver bridge design has the primary function of withdrawing the firing pin to allow the bolt to rotate on opening. The fact that it also prevents the firing pin from forward movement untill the bolt is nearly locked was concidered insignificant since the hammer interaction with the bolt was designed to prevent slam fires. The receiver bridge also acts to re-enforce the receiver and support the rear of the bolt, but should not be concidered a high stress area."
Springfield Arsenal was usng firing pin springs as far back as the Allin Conversion to Civil War Muskets and of course in the Trapdoor rifles. The spring was a safety device to ensure the firing pin did not remain forward and puncture the rim of a rimfire or the primer in a centerfire cartridge prematurely upon closing the trapdoor block. From a manufcaturing point of view, it also protected the nose of the firing pin and kept it retracted so it would not interfere with loading the rifle. So depending on who you spoke with, depended on what the person thought was the most important aspect of the firing pin spring.

The M1 Garand and M14 do not have a firing pin spring in them to keep the firing pin retracted UNTIL it is the proper time to fire the rifle. The "foot" of the firing pin hitting the safety bridge keeps the firing pin back and allows some of the transfer momentum energy of the bolt and firing pin going forward to be "bled off" by hitting the bridge. The firing pin STILL hits the primer every time you load an M1 or M14 and you can easily see that if you eject a cartridge without firing it. There will always be a small indent in the primer when you do that. Now, IF there was no foot on the firing pin, the firing pin could still have enough energy to set off a primer when the bolt goes home.

The very early firing pins for the Garand were fully round in the body and did not have that long milled relief cut in them. One reason they modified the firing pin from full round to that long milled cut was the full round firing pin STILL had enough mass/weight that it set off the primer during loading occasionally. NOT a good thing. The other reason was that long milled cut gave room for "gunk" to get into the bolt and the firing pin would not freeze up. So depending on who you talked to, would depend on what they thought was the most important feature of the fring pin modification from full round to milled extensively.

So when the firing pin was designed WITHOUT a spring to keep it back to ensure firing pin would not set off the primer prematurely, they had to do something with the firing pin so it would not do that. The tail hitting the safety bridge kept that from happening along with the lightened/long milled firing pins.

Yes, the safety or receiver bridge also causes the firing pin to cam/rotate so it clears the receiver and the bolt can go to the rear during firing or disassembly. BUT if the firing pin did not have a tail and had a firing pin spring, there would be no reason to have a tail on the firing pin and thus no reason to have something that caused the firing pin to be cammed so the bolt could be brought to the rear.

This of course doesn't mean a slamfire can't happen.

[Larry Gibson]

A design/spec feature is also the rear of the bolt and face of the hammer. There is a bridge on the rear of the bolt and a corresponding recess in the face of the hammer. If the bolt is not rotated into locked position the bridge is not vertical and the hammer will hit it instead of the firing pin. The cartridge will not fire.

Additionally the face of the bolt and front of the extractor push the cartridge into the chamber. The firing pin can not reach the primer until the case is headspaced and the extractor snaps over the rim of the cartridge as the bolt rotates closed. If the bolt does not rotate closed an inspec firing pin can not reach the primer until the bolt is closed and locked.

Those are two additional safety features in addition to the receiver bridge that prevent out of battery firings in inspec M1s.

An out of battery slam fire can not happen either for the same reasons. In an inspec M1 the bolt must be closed for it to fire. The bolt face can not even smash a protruding primer with out the bolt being at leased partially closed/locked.

However, an out of spec firing pin (broken, stuck, etc.) protruding from the face can cause a "slam fire" prior to the bolt closing. In some cases a soft or weakened primer may also be fired by the inertia of the firing pin. In either of these cases an out of battery firing usually does not occur because the rifle is either partially in battery or fully so when the cartridge fires.

[Larry Gibson]

the odd thing is the case getting all jacked up but not enough op-rod pressure to bend it.
high pressure is usually high pressure everywhere.....

Not necessary, as it all depends on the actual rise of the time/pressure curve. Some pressures rise to peak pressure very quickly and also let off quickly so by the time the bullet exits the barrel the pressure is pretty low. A good example would be a max load to 60,000 psi of Bullseye.....the pressure would peak very quickly and by the time the bullet passes the gas port of an M1 there is not enough pressure nor volume of pressure (functioning requires both) to function the action.