FN Mauser Strength

[Old Ugly]

I have an opportunity to buy an FN Mauser rebarrled in .338 Win Mag. But I am hesitant to make the purchase because it is a surplus military action which means it has the thumb cut on the left side of the action which weakens it, and since I have heard stories of this, on occasion, leading to problems, I fear that a hard kicking round like the .338 my be a bad choice to use with this action. What do you guys think, am I just being to paranoid?

[PetahW]

.

I think that, if I wanted a .338 Mag, and the Mauser was both in good condition (have the bolt lugs & action checked for cracks) & inexpensive enough, I'd scoop it up.

For proud money, though, I'd let it go to the next guy.


.

[Bart B.]

That thumb cut weakens the receiver where it's at, not up front where the locking lugs are.

[Slamfire]

I have an opportunity to buy an FN Mauser rebarrled in .338 Win Mag. But I am hesitant to make the purchase because it is a surplus military action which means it has the thumb cut on the left side of the action which weakens it, and since I have heard stories of this, on occasion, leading to problems, I fear that a hard kicking round like the .338 my be a bad choice to use with this action. What do you guys think, am I just being to paranoid?

Many rifles were sporterized from old military actions for cartridges that I do not think appropriate for the action or the materials. That action was designed and built for the bolt thrust of an 8mm Mauser. As such, a new receiver is perfectly adequate to hold the cartridge thrust of a cartridge in the range of the 8 mm Mauser. However, a 338 Win Mag is a much larger diameter cartridge and owners want magnum level performance, which means, high pressures.

Based on a look of the materials used in these things I don’t think these Win Mag or Weatherby Magnum conversions are appropriate.

I know some are going to point that the following data is on WW1 rifles, but based on an examination of Hatcher’s Notebook, I think the Germans used the same steels all the way through WW2, and so would, I expect, FN.


Rifle & Carbine 98: M98 Firearms of the German Army from 1898 to 1918 Dieter Storz

Inside Dieter’s book are the material specifications for the M98 Mauser.

The material looks to be a manganese steel alloy, with copper added for easy machining.

I assume the material is in the normalized state, but the property requirements were

Ultimate 78.2 Ksi, Yield 36.9 KSI, elongation 15%.

Carbon LT 0.40%
Manganese LT 0.90%
Copper LT 0.18%
Silicon LT 0.30%
Phosphorous LT 0.04%
Sulphur LT 0.06%

Closest I can find is 1038 Carbon steel,

Carbon 0.35-0.42%
Manganese 0.60-0.90

Typical uses include machine, plow, and carriage bolts, tie wire, cylinder head studs, and machined parts, U-bolts, concrete reinforcing rods, forgings, and non-critical springs

Could not find data for heat treated 1038 steel, which makes me think this steel is no longer used in severe applications that require heat treatment.

For AISI 1030 Carbon Steel

Carbon 0.270-0.340
MN 0.60-0.90
1 in round bar, water quenched from 1600 F, 1100 F temper
Ultimate, 84,800 psi
Yield 63,100 psi


Many of today’s receivers are made of 4140. I picked a mid range heat treatment for comparison. For a 1 in round AISI 4140 Steel, Heat treatment normalized 870°C (1600°F), reheated 845°C (1550°F), oil quenched, tempered 595° (1100 F)

Hardness, Rockwell C 34 Converted from Brinell hardness.
Tensile Strength, Ultimate 148000 psi

Tensile Strength, Yield 132000 psi

Elongation at Break 19.0 %

If that receiver was made from modern alloy steels I would say, hey it probably has the margin of strength to reliably hold the bolt thrust of a 338 Win Magnum. But, this receiver is not made of modern materials, has been through one service lifetime, and I am of the opinion that these belted magnum conversions are not appropriate for these military actions. Whatever load it is carrying exceeds original design limits and given the age, material technology, I would say, it is a risk. While I am certain the rifle has fired a number of rounds, who knows how many more rounds it will take to crack the lugs.

Unless you could buy the rifle for a pittance, I would look for a 338 Win Mag in a more modern action.

[Jimro]

An FN K98 action in 338 Win Mag is just fine. The FN's are among the better actions to build on, along with Czech and pre-war German actions.

The comparison to 1030 steel isn't exactly a good one, as you aren't looking at the actual thicknesses of steel used. But k98's will be proofed above 70k psi, which is supposedly above the burst strength, but since the receiver is thicker than the referrence thickness it holds together just fine.

Jimro

[Paul B.]

The only difference between that milsurp (?) FN Mauser action and the FN Brownings made in the 60's and 70's is basically cosmetic with the Browning having a different but not better bolt release and better cosmetic finish like shiney bluing and a fine metal polish. I have several rifles built on milsurp Mauser action including a WW1 Oberndorf action on my .35 Whelen My .280 REm. is based on a DWM 1909 Argentine Mauser and I load both round well above SAAMI specs. I would trust that FN Mauser the OP is talking about a hell of a lot farther that any 1903/1903A3 Springfield Most of my sporters are based on Mausers of one type or another but most are on FN's and they're just fine.
Be nice if we could see pictures of the subject rifle.
Paul B.

[csmsss]

Slamfire, do you have any evidence that FN used the same steel as German manufacturers? Wouldn't it be far more likely that they used the same steel in their Mauser-licensed receivers that they used in their other rifles?

[Mobuck]

The "thumb cut" doesn't weaken the action so much as make it somewhat more flexible causing a potential accuracy degradation.

[Old Ugly]

Paul B., the gun is for sale on gunsamerica so providing photos is easy. Here's the page.

http://www.gunsamerica.com/976498753...STER_MAGNU.htm

Just click on the image and there will be more photos.

[Old Ugly]

Crap, someone just sumbitted an offer to buy it. Well, there probably goes that. Sorry to bother you guys.

[44 AMP]

FWIW. I have a .458 Win Mag built on an Argentine 1909 action, and its handling the recoil just fine.

Done right, and FN does them right, its not a problem.

[Jim Watson]

The crest is Venezuelan.
As best I can Google, they bought bolt action rifles from FN from 1930 up into the 1950s until replaced by the SAFN 49 automatic and then the FAL.

It looks like a nice sporterizing job, but $795 seems a bit high. Somebody is willing to pay it, though.

[Paul B.]

OK, the crest is from Venezuala and I'd bet money the gun was originally 30-06 or maybe 7.65x53. Just my not very humble opinion but FN makes very good guns. The thumb cut probably won't hurt squat. My very expensive (to me anyway) .280 Rem. is bases on a DWM made Argetntine Mauser and that rifle is sub-MOA as is my custom .35 Whelen on an original Oberndorf action. I also have two rifles based on Steyr Mauser actions in .308 Win. and another Steyr military in 7.62 NATO. The all have thumb cuts. Makes the rifle infintesimatly lighter by maybe a half ounce. Nice looking rifle but I do think the price is a bit high. However, I have been known to pay way more that a rifle was worth if I wanted it that bad. I hope you know that a .338 Win. Mag. does have a bit of recoil. I shoot a Ruger #1 in .416 Rigby with that assine little piece of red rubber Ruger calls a recoil pad and that gun hurts me less than the two Winchester M70s I have in the .338 Mag.
Paul B.

[Slamfire]

Slamfire, do you have any evidence that FN used the same steel as German manufacturers? Wouldn't it be far more likely that they used the same steel in their Mauser-licensed receivers that they used in their other rifles?

I have not seen any metullurgical data on FN, CZ, Mausers except for the Swedish Mausers. The Swedish M1896's were made of plain carbon steels through out production. I have not seen any documentation that any pre WW2 or WW2 bolt actions, except for the nickle steel 03's were made of alloy steels.

The actions were not designed or built to take any cartridge loads except for issue ammunition. However, people are welcome to explore, push bounderies, and shoot any cartridge they want through their old military action.

Sometimes nothing happens beyond design limits, sometimes unfortunate things happen.


To chamber and shoot these old actions in cartridges they were not meant or built to handle, is after all, an individual decision. My decision is to stick with something I feel comfortable behind.

The comparison to 1030 steel isn't exactly a good one, as you aren't looking at the actual thicknesses of steel used. But k98's will be proofed above 70k psi, which is supposedly above the burst strength, but since the receiver is thicker than the referrence thickness it holds together just fine.

I don't have better data. The data comes from places like mat web and I chose data for the same size of article. To get load you multiply psia by crossection, and these things were designed to carry load. It is just easier to discuss things in psia. Actual receivers and bolts are of different thicknesses and I am not going to take actual measurements and try to reverse engineer the design margins. Maybe someone out there with a FEM wants to do that, and I hope they share the information.

I really doubt that any proof test was made at pressures or loads above the ultimate tensile. Proof testing is a historical artifact, back in the 1600's, steel and quality was so varible that proof testing made sense. By the time you get to the 1940's, I believe a proof test something they did because they always did it. Now, I consider individual proof tests in the same context as an appendix. It had a function at one time, but, why is it there, what does it do? If the assembly process control is so bad that each firearm has to be tested at extreme limits, or bad ones might go out the door, then the factory needs to be shut down.

[RC20]

The only proof test that works is if you follow it up with a NDT, i.e. magnaflux like the military does on the M16/M4 bolts.

A proof test means it did not blow up. It may have weakened the item, so that each subsequent standard load stresses it a bit more.

If it weakened it but in its normal life not shot that much it may never fail

On the other hand it could go over the edge on the next shot.

Statistically its probably valid but there will be the odd outlier that slips through the cracks figuratively and literally.

Personally if I wanted a 338 magnum I would buy a used one, old Rugger 77 or the like or one of the new low cost options.

[George4376]

Roy Weatherby used FN Mauser Actions when he first marketed his rifles,and Weatherby Magnum line of ammo. He had no problems with the action that I have heard of.

[Bart B.]

A ballistics engineer at Lake City Army Ammo Plant told me decades ago that anyone making proof tests firing proof loads certified to produce spec'd proof pressures in pressure barrels, had better make some measurements after firing each proof load.

Why?

Well, the rifle may not explode but its headspace may open up a thousandth or more. Which is proof the bolt or receiver is too soft and subsequent firing of proof loads will probably stretch it more. Some folks proofing barrels even mic the barrel diameter around the breech; too soft a barrel will expand, too.

The object of proof loads is to test the rifle's metal to ensure it doesn't stretch at all. Exploding barrels and actions is not part of the proofing process; that only means the barreled action should never have been proofed in the first place. Few people measure anything to see if the barreled action stretched at all using loads way over normal maximum.

[Paul B.]

It would seem to me that if those ex-military Mausers, I'm talking the M98 now and not the weaker 93 and 95 Mausers, that if they were such poor choices, why would anyone use one to make a custom sporter out of one?
Why would prestigious custom gunmakers use those Mauser actions if they were no good and unsafe?
I would buy a sporter based on a milsurp 98 Mauser way quicker than one on the vaunted and revered Pre-64 M70 Winchester and yes I've over several of the Pre-64s.
I doubt that any company is going to build a firearm designed for war to build a piece of junk. That would ruin their reputation and the country ordering would not accept them nor would they pay for them.
Paul B.

[reynolds357]

In time of war armies will buy junk if that is all they can get. The Mausers are as a whole good actions. The MarkV Wby is the best non custom high pressure action, and the good quality 98's are not too far behind.

[Hawg]

I've seen Mausers rechambered to .338 and 30-338 and the only issue I've heard of is sometimes feeding issues if the feed rails aren't reworked properly. I'd be more concerned about that than any pressure issue. Ask me and I say you're being paranoid. BTW I have an F.N. I've been shooting hot 30-06 loads out of for over 30 years.

[Mobuck]

Judging ALL similar make/model rifle actions by the capabilities of some can be dangerous.
I determined that the American Enfield (P17) was one of the stronger actions and had a 257Wby built on that action. Unfortunately, mine had been over-annealed during the drill and tapping process. After about 100 shots, it disintegrated and nearly killed me.
This is the hazard of ANY unknown 75-100 year old action that has seen no-one knows what abuse. After surviving that incident, I vowed to never own or shoot a rifle that is chambered for a round producing more pressure than it's original chambering. There are plenty of modern rifles that usually dollar out cheaper than "building" a surplus clunker.

[Jimro]

I don't have better data. The data comes from places like mat web and I chose data for the same size of article. To get load you multiply psia by crossection, and these things were designed to carry load. It is just easier to discuss things in psia. Actual receivers and bolts are of different thicknesses and I am not going to take actual measurements and try to reverse engineer the design margins. Maybe someone out there with a FEM wants to do that, and I hope they share the information.

I would like to see that data too.

However decades of both custom and factory m98 actioned rifles in 338 Win Mag and 458 Win Mag give me a pretty good idea that an M98 action is perfectly adequate for the task.

Obviously if the action is damaged somehow that is obviously not the case, but that is true of any action.

Jimro

[Slamfire]

Roy Weatherby used FN Mauser Actions when he first marketed his rifles,and Weatherby Magnum line of ammo. He had no problems with the action that I have heard of.

So why did Weatherby develop the Mark V action? Weatherby was using post War, commercial made FN actions, not military actions that had gone through one or two rebuilds. I suspect Roy did not want to publish the number of FN actions that came back to his shop with cracked bolt lugs and developed the Mark V action because there was no commercial action on the market that could hold up to the constant pounding of Weatherby cartridges. Frank De Haas, in his book “Bolt Action Rifles” did not consider the post war FN #5 action suitable for belted magnums. Actually he sort of qualified it, it was suitable for low pressure factory 300 H&H and 375 H&H, but not for reloads. One customer of his, with 300 H&H reloads, cracked the rifle lugs.

Why would prestigious custom gunmakers use those Mauser actions if they were no good and unsafe?

Prestigious assumes a lot of things. I am not going to assume the education level of any prestigious gunmaker, nor am I going to assume the guys warrant their work. You supply the action, they build it into a rifle, if you blow up one of their creations, it’s your problem, not theirs.

I have read a number of threads posted by “gunmakers” who have totally bought into the mystique of “old world craftsmanship” with old obsolete military actions. They don’t have a technical basis to support their emotional outpouring for old actions. They will however, take your money.

I doubt that any company is going to build a firearm designed for war to build a piece of junk. That would ruin their reputation and the country ordering would not accept them nor would they pay for them.

FN built military actions that were perfectly suited to the cartridges for which they were chambered. I am certain FN does not warrant their old military action 70 years after manufacture and decades after being junked as obsolete military equipment. Nor do I expect will they recommend that their old military actions be in continuous use, or be used in belted magnum applications.

I am not going to do it, but I would be interested if anyone will take the time and effort to contact FN and ask them “Will you replace at no cost one of your WW2 era military actions if it breaks in use?”, “will you cover any medical costs if an injury results?”, and “are your military actions suitable for conversion to belted magnums?”

Here is contact information for

FN Herstal
Voie de Liege 33,
B-4040 Herstal,

Tel +32 4 240 8111.

Email: [email protected]

Let me know their reply.

[Slamfire]

I determined that the American Enfield (P17) was one of the stronger actions and had a 257Wby built on that action. Unfortunately, mine had been over-annealed during the drill and tapping process. After about 100 shots, it disintegrated and nearly killed me.

This is interesting and I am glad you recovered. We are in agreement over your point about the questionable condition of old military surplus rifles and for not using them for cartridges that are overpressure and have more bolt thrust than for which they were designed.

But I would like to ask some questions, if you have the time. I have heard that many Eddystone receivers were brittle due to being overheated in the forge room. Are you sure it was due to annealing?

A bud of mine purchased a M1903A3 that had been converted to a drill rifle. I got to examine the receiver and it was mint looking, no evidence of a tiny tack weld that had been on the bottom. But, the receiver ring had been heated in the process and lost its heat treatment. He shot it with a new barrel and the headspace increased. He put on a new bolt to take up the headspace and after firing, the headspace increased more. If he had continued to shoot the thing he would have developed indications of excessive headspace. There is no guarantee his action would have failed gradually, but I think it is probably that would have been warning signs, such as difficult bolt lift or case head issues, before it would have blown. However, a failure due to a brittle receiver would be sudden. So, what did you see and how did it happen?

[George4376]

Slamfire When did all these unfit Weatherby actions start blowing up? Sounds strange to me,If FN Weatherby actions had a problem I'm sure someone other than you would have heard of it.