7mm Rem Mag Catastrophy

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pcar916

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7mm Rem Mag Catastrophe

About 20 years ago I did a bad thing. I accidentally put an 8mm cartridge in a 7mm Rem Mag Mauser and pulled the trigger. The bullet made it out of the barrel.

Fortunately God, the gas relief hole on the receiver, and eye and ear protection saved me from anything but a stinging face and arms. After a serious sit-down with myself on stupid procedures I corrected the problem of having two guns (and calibers) on the bench at the same time and put that particular gun away until this morning. I still have all of the metal parts. What's left of the stock is hanging on my office wall as a constant reminder to concentrate. No amount of flames can beat me up worse than I already have folks. Now...

1. How many gunsmiths can MagnaFlux the receiver and bolt to see if they are still viable? Will I have to find an industrial machine shop to do it? The barrel is a massive varmint version, not a hunter.

2. I can't tell any difference in the lugs but don't have a good way to check the front lug engagement areas in the receiver. So if I get a good headspace are the lugs ok assuming the MagnaFlux results on the bolt are good?

I've bought the Jerry Kuhnhausen's Mauser shop manual but before I start into it this afternoon I thought a forum question or two would be a good thing to do.
 
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I've not had a reciever examined by magneflux, but you don't want cracks, so that's a perfectly reasonable thing to do. I would expect, rather simply, if there are no cracks and if the receiver dimensions are still correct, the yield of the steel was not exceeded and it is fine.

Headspace should tell you about the lugs. Did you get any gas cutting on the bolt? If you remove the barrel and mount the receiver in a lathe or upright on an X-Y table on a mill or even on a drill press, you should be able to use an indicator with a dogleg probe to tell if the receiver was pushed back by the bolt lugs.
 
With the shape and small intricate angles etc., I don't know if Magnaflux will tell the story, the powder may give false indications. Dye penetrant applied correctly and inspected very closely may be more accurate.
If it were mine I would talk it to a testing company and see what they recommend, x-ray would probably be the most thorough.
Good luck with it!
 
Thanks folks,
Never mind about the bolt. The attached image shows it's tongue ahead of the split lug is broken off. So now the receiver is to be tested and find a replacement bolt and bolt-release for a Mark X. Sure wish this was going to be as easy as the "screwable" headspace on my Enfields!
 

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That's why I asked about the gas cutting. Usually if a case head lets go, the bottom of the bolt is either cut or has part blown off, just as you've discovered. New bolt time, at the very least.
 
Most large welding shops have Magnaflux equipment, but not all will use it on other than their own work. You might call around and tell them what you want done and that it is on a gun. Or ask a local gunsmith if he does it (probably not) or knows someone who does.

Remember that when the bolt is closed, that part is up, so the brass and gas may have escaped without getting into the left lug raceway. If it did, then the left receiver rail may be bent or even cracked, and that is the area you especially want to check. I doubt the bolt lug seats are damaged, but it is possible; a headspace check should tell you that.

I assume the 8mm you mention was an 8x57. If so, the smaller case likely let go before pressure had built up very high, or there would be more damage than that.

Jim
 
Thanks,
I'm also glad that wasn't a stronger case. I'll check the lug areas and rails (best I can without removing the barrel) then and include a picture of the 8x57 brass (still have it) inserted back into the bolt in the position it blew out. It was still stuck in the chamber after I pulled out the bolt

Before I wire-brushed the bolt earlier today to get a better look at the broken piece, the carbon deposit on the bolt face showed clearly that the case blew out directly toward the broken area. The pressure didn't only escape out the vent hole in the left-front ring, but also into the magazine. The magazine bent out sideways and broke the stock on both sides. At the same time the door flapped open and dumped the remaining cartridges onto the bench.

At the time I had no idea the 8x57 cartridge would chamber in that rifle, but I remember that it took a tiny bit more effort to get the bolt closed on that round. I thought that was a bit odd, but it didn't raise a red flag then. I was experimenting with bullet-seating depth at the time and had intentionally tried to seat those 7mm bullets a little closer to the landings based on the cartridge mic I had used in that chamber. Attention to detail at that point would have saved my rifle. All things considered it was a cheap lesson, but a painful one.

I looked online for some sources for a bolt, but none turned up yet, Sarco doesn't have them that I can find either on their website or in Shotgun news. I'll have to make some calls on Monday unless I can find one before then. I have a K-98 bolt (not a spare) that seems to work smoothly in this receiver. I'll look up the case dimensions and mic the two bolts tomorrow.

From my reading so far am I correct that, unless I can find a long bolt that's already a belted magnum caliber, I'll have to open up the bolt face, head-space the gun, and tune the extractor?
 
I have a portable magneflux machine, it works on receivers like the M1917 Eddystone and LN Springfield, other receivers that are subject to stretch are not likely to crack.

As to what happened to the bullet, not the first time a large diameter bullet was chambered in a small diameter barrel, a man was asked to zero a rifle for a friend, he perchased 308 W for a 25/06, long story, the rifle survived, my opinion, the bullet did not exit the barrel 2"+ long, the bullet came apart at the throat, the lead core was stripped from the jacket. the jacket left after the lead core. No one was interested in walking the range.

Any one can take a receiver to a machine shop to have it magnefluxed.

I am the only fan of knowing the length of the chamber before firing, without knowing when the rifle is rendered scrap the shooter does not have anything to compare the before and after with, the next best thing is a fired case.

Not something anyone else would do but the minimum start would be to remove the barrel and then check case head protrusion on the barrel (.110 + or - very little) then compare the case head protrusion measurement with the distance from the front receiver ring to the bolt face, and the shank shoulder at the end of the threads should contact the fromt receiver ring when the barrel is secured. I bottom out the barrel face to the seating ring then measure the gap between the front receiver ring and shank shoulder with a feeler gage.

I purchased 5 receivers that were suspect, I had four bolts, I compared the effect each receiver had on head space, I compared each bolt for the effect each one had on head space, regardless, any bolt with any receiver resulted in a maximum of .0015 difference. I used one barrel to test fire all five receivers.

In an effort to reduce head space on an 03 Rock Island I offered to measure the effect each bolt had on head space, the Rock Island had .0075, I have 30 plus Springfield bolts, he has 70, I told him it was a waste of time, the 03 period correct bolt has a straight handle, I have one, he had one and was not going to settle for a rifle that was not period correct for 1911 and he was not going to move the barrel back 1 thread.

Point? The bolt face must be opened for use with the 7 Remington Mag, the effect the bolt has on head space can be measured, finding someone that is willing to take the time to measure is another matter, they will send you three in hopes one will work, then there is a good chance there is not .001 thousands difference in all three.

F. Guffey
 
I don't have a barrel wrench or action vice so, at least for now, I don't have the right tools to remove or reinstall the barrel. But I might be able to get my hands on a bore scope to inspect the chamber and throat area.
 
Just a thought, the case failed, not the receiver or barrel. The case was too small in diameter for the magnum chamber, the case was too short for the Magnum chamber, the bullet managed to escape but not before the pressure exceed the ability of the poorly fitting case to hold the pressure, not a design but the case head compresses, yields, and or crushes when exposed to high pressure, we do not know 'by how much' but when the case head compresses the effect it has on case head separation is the same as excessive full length sizing, we know the case was not held to the rear and we know it could not head space on the shoulder of the chamber, so the compression of the case head due to the obstruction and the poor fit between the case and chamber caused the failure.

The question, did the case head expand because of excessive high pressure, did the case upset, expand or yield. ? Did the primer pocket expand enough to allow the primer to fall out, did the flash hole increase in diameter??? As to the last question about the flash hole, I know of one person that measures the diameter of the flash hole, then drills them, all, to the same diameter, he is just north of you.

Without the tools it could turn into 'starting over' for you.

F. Guffey
 
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im just glad you came out of it safe. as the saying goes in school we give you the lesson then you take the test, in life you take the test and then get the lesson.

im glad you came from this test with the right lesson and i hope your honest story permits others to do the same.
 
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