Got this from Mims, he got it from a gunsmith friend of his. Here is what the gunsmith told Mims.
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Shooting normal reloads. .264 Win Mag.

It's not the ammo. Pressures sufficient to do this would have turned the brass into Play-dough. It's a metal failure but I've no clue why. This is a commercial FN Mauser that has been in service for many years.

Customer found a new receiver/bolt and I'll rebuild his rifle with those parts.

Thank God for the Mauser third "safety" lug.

This is the first time I have ever seen such a thing. I couldn't "see" it at first and spent a few moments checking headspace to determine the cause of the head separations.

WOW!

that's all i an say.. and not a failure mode I've ever seen before, and hope to never again
jeffe

Lets here it for the 3rd lug.

Now I'm going to be checking bolts half the night...

Frank DeHaas wrote of this FN Mauser failure in his book "Bolt Action Rifles". It is on page 176 and his description sounds just like this photo.
I agree with his analysis of the of the failure. In his example the failure occurred with a 300 H&H configuration which has the lower shoulder partially cut away. Basically he says the receiver yielded until the upper lug (the split lug) was carrying most of the load and it cracked.
In the photo shown here the shooter might not have noticed the failure early on and shot it until the bottom lug cracked too.
You will notice the upper lug is damaged far worse than the lower. I have always thought the corner of the locking lugs and the bolt body needs a bit of a fillet radius to help prevent this on all bolt guns.

Because of this I would not use any standard Mauser with a large diameter case at high pressure especially if it were to planned for hard use.

Ireload has a good point except the .264 Mag didn't have the receiver cut away like a 300 H&H chambering would have had.
That said it does appear that the lower lug wasn't in contact with the receiver and the upper lug was carrying the weight...just as predicted....just a guess.

I drew some arrows for discussion.

The Red and blue arrows are typical of heat treat fracturing. I've never seen it on a bolt but on many other parts where the failure actually started in the quenching of the heat treat process and shows up later in the life of the product......not saying that's what this is....but those two cracks are easy to understand as they always start at a corner (fillet)!!

The black arrow points to a crack that just plain defies logic!!!!

So, if I understand this correctly, it seems that, according to DeHaas:

1. Too much metal was cut away behind the lower lug recess.
2. As a result, the lower lug set back the lower lug recess to the point that the upper lug began bearing all of the burden.
3. As a result, the upper lug cracked.
4. Firing with the cracked upper lug caused the lower lug to again begin bearing on the set back lower lug recess.
5. At this point, the lower lug was bearing all the burden and it, too, finally cracked.

Makes sense, I suppose.

But, as vapodog has indicated, DeHaas was talking about a "long" magnum like the .300 H&H Mag.

The pictured bolt was supposedly from a .264 Win. Mag. - one of the original "short" magnums. So, metal removal from behind the lower lug recess shouldn't have been a factor.

Or are FNs so different from other '98 Mauser derived actions that they are uniquely susceptible to this kind of thing?

quote:

Or are FNs so different from other '98 Mauser derived actions that they are uniquely susceptible to this kind of thing?

The FNs are nearly identical to todays Zastavas with the possible exception of metallurgy.

The Zastavas are also seriously undercutting the front ring for 375 H&H rounds. They seem to get away with it!

mrlexma,
Your 5 points are correct.
DeHaas' example was the FN factory H&H version.
The FN H&H length version was manufactured with the lower shoulder relieved for the longer cartridges.
I will add that the FN 30-06 length actions that I have messed with have slightly less metal behind the lower lug than the original German design though as I remember it is only about .050.
I think that relying on the short magnum version providing safety compared to the H&H version might be a case of splitting hairs. That is, I would just pick something stronger for a fat high pressure round.

The FN commercial is identical to a 98 except for the thumb cut and the charger guide features (and the magazine length noted above). Military FNs are identical in design to the German military receivers.
Later versions of the FN commercial action have the double cut collar instead of the C collar.

Mausers wheather FN, German or Czechs rely on a hard skin and a soft core. The hard skin is not very thick. This permitted the use of less expensive steel. I am not sure any of them are adequate for hard use with reloads just below the limit of primer pocket expansion... with the belted magnums. Add oil in the chamber say once in about 10 to 20 rounds due to cleaning and you might get one to break.

quote:

Originally posted by vapodog:


Ireload has a good point except the .264 Mag didn't have the receiver cut away like a 300 H&H chambering would have had.
That said it does appear that the lower lug wasn't in contact with the receiver and the upper lug was carrying the weight...just as predicted....just a guess.

I drew some arrows for discussion.

The Red and blue arrows are typical of heat treat fracturing. I've never seen it on a bolt but on many other parts where the failure actually started in the quenching of the heat treat process and shows up later in the life of the product......not saying that's what this is....but those two cracks are easy to understand as they always start at a corner (fillet)!!

The black arrow points to a crack that just plain defies logic!!!!

The black arrow crack might have started in the fillet on the other side and cracked across the lug on a crooked line. Other than that it makes no sense to me either.

Thats not uncommon with Mausers. A member PM'd me that the bolt lugs sheared off of his Mexican Mauser.

quote:

Originally posted by Bill Soverns:
Lets here it for the 3rd lug.

That's why it's there!

The 3rd lug is an expensive band aid that would not be necessary with better quality steels, process controls, heat treat and a little bit more design work.

quote:

Originally posted by ireload2:
The 3rd lug is an expensive band aid that would not be necessary with better quality steels, process controls, heat treat and a little bit more design work.

I'm sure I'll be corrected if I'm wrong here.....but all bolt actions have a third safety lug. It's just that it's often the bolthandle engaged into the rear of the receiver and isn't shaped like a lug as the Mauser is.

M-98 bolt handles do not engage the receiver!

quote:

Originally posted by vapodog:

quote:

Originally posted by ireload2:
The 3rd lug is an expensive band aid that would not be necessary with better quality steels, process controls, heat treat and a little bit more design work.

I'm sure I'll be corrected if I'm wrong here.....but all bolt actions have a third safety lug. It's just that it's often the bolthandle engaged into the rear of the receiver and isn't shaped like a lug as the Mauser is.

M-98 bolt handles do not engage the receiver!

Yeah, I'll buy that, Vapo. But do you really want a Remington bolt handle for your third lug?
And how about that big ugly-ass gap around the post 64 handles?

quote:

Yeah, I'll buy that, Vapo. But do you really want a Remington bolt handle for your third lug?
And how about that big ugly-ass gap around the post 64 handles?

stir

are we having fun today or what?????

quote:

Originally posted by vapodog:

quote:

Yeah, I'll buy that, Vapo. But do you really want a Remington bolt handle for your third lug?
And how about that big ugly-ass gap around the post 64 handles?

stir

are we having fun today or what?????

I don't know about you, but I sure am!

Regards,

Don

quote:

I don't know about you, but I sure am!

Regards,

Don

dancing

quote:

Originally posted by vapodog:

quote:

Originally posted by ireload2:
The 3rd lug is an expensive band aid that would not be necessary with better quality steels, process controls, heat treat and a little bit more design work.

I'm sure I'll be corrected if I'm wrong here.....but all bolt actions have a third safety lug. It's just that it's often the bolthandle engaged into the rear of the receiver and isn't shaped like a lug as the Mauser is.

M-98 bolt handles do not engage the receiver!

Vapodog,
You are correct with the exception of the double ugly Lee-Enfield and MAS which are of no importance in the context of this discussion.
The 3rd lug on most bolt guns is one of convenience adding little to no cost. They have little to no value when the bolt and receiver are made of materials that do not fracture or set back.
The 98 mauser style 3rd lug adds extra an extra operation to the bolt to leave the lug and hog off the other material. Probably the equivalent of $5 in today's world on the bolt alone. But it can be done with standard equipment. The locking lug recess would be twice that much and would require specialized dedicated equipment to do it in any quantity. I know an extra $15 does not sound like much but it adds up and I would prefer it be spent on a little better steel and heat treat if I was working on a belted magnum.

I had a FN 264WM,now I have FN/Douglas 264WM.The FN barrel chronyed real slow,max 2950 or the primers dropped out.When it was rebarreled ,only one lug was found to be touching.Mine came out of a an estate,"as new" ' 68.It was,the extractor was a .473.Could have been the same time frame.

New Photos and more info from the gunsmith.









The Blue arrow points at a scuff -- not a crack.

The lower locking lug abutment is not unusually lowered or reduced in length. The receiver appears undamaged.

There was at least one shot fired after the initial problem of head separation/ hard bolt lift. It's certainly possible that the lugs fractured sequentially.

The "safety" lug of a '98 Mauser does not normally make contact with the receiver until and unless the primary lugs fail. I'd guess that in this case, after the first problem shot, it was all that kept the shooter from sporting a new "hood ornament."

I don't know about rebuilding the rifle with another bolt. When do you figure that a given rifle action has used up all it's good Karma? For me it would be the first time it broke without me getting hurt!.............DJ

Too many high pressure rounds. Metal fatigue. Considering some of the reload velocities people put up, I am not surprised this doesn't happen more often.

Without serious analysis it is all speculation anyway.

Please post pics of the handle area particularly the root if you have them. That may tell us some additional info about the nature of the failure.

quote:

Originally posted by ireload2:
The 3rd lug is an expensive band aid that would not be necessary with better quality steels, process controls, heat treat and a little bit more design work.

I'm sure the Mauser brothers would be happy with your report.

How many actions have you designed and built, and were they produced in the numbers that the Mausers were.

Those actions are theoreticaly 108 years old. Think you'll get that old without any parts failures?

quote:

Originally posted by vapodog:
......not saying that's what this is....but those two cracks are easy to understand as they always start at a corner (fillet)!!

Maybe nothing to do with it, but my bolts show some sort of cutting work around the rear base of the lugs. Worries me a bit seeing as cracks like to start in corners.
And I don't think the M96 Swed has any 3rd safety lug.

I'd have to agree with nitroman.Lots of variables -machining [radius at fracture point, machining quality ] heat treatment [ case depth ,hardness ,decarburization etc] how many hot loads .A guess -fatigue failure from too many hot loads with other factors adding to it.

I have seen the same happen on a FN in our area. The action was "new" and the caliber was also 264. The bolt face failed in the same manner. Later inspection found the bolt body over all was way to hard when tested on the "C" scale. The owner developed his maximum in the winter and then shot the same loads in late June. After the failure I was asked to check the action for lug-seat set back and found none nor any other damage to the action or barrel. A retro-fit bolt was installed and properly head spaced and he is shooting the rifle to this day. He no longer tries to drive 140gr bullets at 3300fps. I have seen more heat treat issues with FN actions than any other comercial 98. I have even seen some in the white actions to be completely soft. You should check every action and bolt before you begin a project. This could save you some hassle.

We don't know what this rifle's owner considers "normal reloads," do we?

An interesting and informative reply by Mr. Echols.

I was going to ask if there was a chance the bolt had been replaced when the rifle was converted.

As pointed out, there are 100 years of mauser bolts floating around out there, some made under worse conditions than others, and in a non-factory build there is always the chance they came from different manufacturers.

quote:

Originally posted by STINGER:

quote:

Originally posted by ireload2:
The 3rd lug is an expensive band aid that would not be necessary with better quality steels, process controls, heat treat and a little bit more design work.

I'm sure the Mauser brothers would be happy with your report.

How many actions have you designed and built, and were they produced in the numbers that the Mausers were.

Those actions are theoreticaly 108 years old. Think you'll get that old without any parts failures?

I am sure the Mauser brothers would not use their original specification for a belted magnum today. Would you?

The FN receivers that I have owned all had a brinnell test indent on the right side of the recoil lug.

Just from looking at the photos that bolt started out as a .473 bolt face and was opened up to the .513 magnum size. It looks to be new--nothing like a bolt that has seen hard use.

I have seen this before on pressure testing of different action,when trying to blow them up.All metals stress and change characterestic through time and can weaken.Has anyone checked its Rockwell hardness at different points? This is truely a rare occurance,but it can and did happen. thanks for sharing this with us. van

I have never seen a Mauser or any other bolt action crack like the above pictures.

I have seen on TV how an oil platform sank from a crack that grew.

Interesting note:

This lug (area in red) only contacted the receiver on about 1/2 of it's face and it caused a bulge of the lug OD.....see the area in blue.

Further.....the lugs must have been faulty as they should have withstood reloading excesses until the case melted and certainly the receiver should have shown setback before this failure happened.

It makes me wonder if the bolt was rehardened with the receiver as part of it's project build.

quote:

Originally posted by DArcy_Echols_Co:
The bolt face failed in the same manner. Later inspection found the bolt body over all was way to hard when tested on the "C" scale.

This is the most likely cause of all those suggested. I agree, the bolt should be almost the last part to fail.

quote:

Originally posted by duikerman:

quote:

Originally posted by DArcy_Echols_Co:
The bolt face failed in the same manner. Later inspection found the bolt body over all was way to hard when tested on the "C" scale.

This is the most likely cause of all those suggested. I agree, the bolt should be almost the last part to fail.

It would not take more than 10 mins to test this bolt and find out what it is.

i just noticed it, but in the first picture, in the extractor groove, there appears to be a crack that is about to seperate the head from the body of the bolt.

It makes me wonder if this bolt was made late in the war when rifles were being made from melted-down alarm bicycles from Holland and when the slave labor running the factories was doing whatever possible to sabotage the product.