? about pressure in 7x57 95 Chilean Mauser

J

jmstr

New member
Hello all,

I have an 1895 Chilean Mauser chambered in 7x57, with the original barrel [as far as I can tell]. It is an Oberdorf factory run.

It has been in my family since the mid 1960s, at least, so I know its condition, and has been completely sporterized.

I understand that reloading for this round requires a combination that does not generate more than 44,000 CUP, according to most listings. I'm ok with that.

What I have a question on is the issue of what limits the CUP: chamber or action?

What I mean is that I have the factory gun [which loves 175grain rounds]. I also an Adams and Bennet small ring Mauser barrel I bought a few years ago [when I thought my chamber/barrel were toast].

I was wondering if changing the barrel, which would change the chamber [or am I not understanding the system correctly], would allow for an increase in chamber pressures?

Or, is it the strength of the action around the barrel/chamber, and the strength [or lack there of] of the bolt system?

I understand that the Model 98/Large Ring Mausers had a 3 tab locking system on the bolt that makes them safer than the 2 tab locking on the small ring Mausers.

I love the model 95 Chilean though, as it has a notch in the action that the bolt drops into that seems to make it a significant step up in strength from a 1893 Mauser that has no such notch to contain the bolt from moving to the rear.

Again, I am NOT arguing that the 95 Chilean's notch makes it the equivalent in strength of the 98 3 tab locking system. I just feel safer with the 44,000 CUP pressures than I would with a 1893 Mauser.

BUT, isn't the chamber part of the barrel? And, if so, would changing the barrel increase the allowed pressure for the round or not?

Keep in mind I would NEVER dream of even thinking to change the CUP pressure in an 1893. And I was only daring to DREAM about raising the 7x57 pressure from around 44K CUP to around 46K CUP, not anything like 48K or higher. AND that was a DREAM.

I have a LOT of mil surplus ammo to burn up first, and then a LOT of bullets pulled from mil-surp ammo to use before I change barrels to one that handles 150gr better.

But, I was curious about if the barrel change might make my gun stronger/safer?

Any thoughts?
 
jmstr said:
I am NOT arguing that the 95 Chilean's notch makes it the equivalent in strength of the 98 3 tab locking system.
I just feel safer with the 44,000 CUP pressures than I would with a 1893 Mauser.
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FWIW, there's NO practical differences, other than very slight cosmetics, between "cock-on-closing" M-1893 & M-1895 Mauser's - AND, they're both made of metal over 120 years old, with God only knows what sorts of stress' placed on them over those years before any of their present owners were even a gleam in their Father's eye.

A Mauser rifle is an integral system, of both barrel design/material, action design/material/hardening (or not), and bolt material/hardening/etc.

Changing the barrel doesn't help a 120+ y.o. action or bolt stay together in front of a shooter's eyes/face.

Yes, we've all shot older guns x-many times w/o incident - but in reality, NOBODY can reliably predict what will happen the next time the trigger's pulled on a live round.



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1893's /7x57 mauser

I have two of them, one is a 1893 Pattern long rifle with a mfg date of 1931 and the other is an 1893, Spanish Carbine, 1916 Pattern, with a mfg date of 1932.
I would guess that the metallurgy of the 30's would be a great improvement over the 1890"s or even the early 1900's, but I still keep pressures low just to be safe.
They are both decently accurate (2"-4" @ 100) and my hand-loads are just a slight improvement over the 30-30 in power.
They are a pleasure to shoot, and plenty good for deer or black bear.
If I need more power or distance, I have other rifles in bigger calibers.
It doesn't make sense to push those old guns beyond their limits, just enjoy them for what they are.
 
They are both decently accurate (2"-4" @ 100) and my hand-loads are just a slight improvement over the 30-30 in power.
Click to expand...

Aye, slightly better than the 30/30 in power .....at the muzzle ....but if they can be made to shoot a sleek 7mm BT bullet ...... then it doubles the effective hunting range of the .30/30.

A bullet with a .500 BC launched @2500 f/sec, and sighted 3" high at 100 will still allow you to hold in the hair at 300, and still be packing well over 1200 ft/lbs of energy when it gets there ....... and if you can make it shoot under 3" @100, it's still pie plate accurate at 300, if you do your part.
 
What I have a question on is the issue of what limits the CUP: chamber or action?
Click to expand...

What is the weakest link?: It is going to be the action.

A M1895 made of modern materials on a modern production line would be as “strong” as many modern actions, minus the better breeching methods that protect the shooter from gas escape from a blown cartridge. Pre M98 actions have virtually no shooter protection features.

People today just do not appreciate how primitive were the manufacturing processes around 1900 and just how limited the knowledge of the properties and characteristics of steel. Post WW1 steel technology advances very quickly and by the time you get to WW2 it is a mature science.

This link is a good review, the M1895 action described here was so poorly made the receiver seats set back:

http://dutchman.rebooty.com/1895Chile.html


This will also give you an idea of the low pressures these early actions were proofed at:

Rifle Magazine Issue 159 May 1995 Dear Editor pg 10

http://www.riflemagazine.com/magazine/PDF/ri159partial.pdf

Ludwig Olsen

Mauser 98 actions produced by Mauser and DWM were proofed with two loads that produced approximately 1000 atmosphere greater pressure than normal factory rounds. That procedure was in accordance with the 1891 German proof law. Proof pressure for the Mauser 98 in 7 X57 was 4,050 atmospheres (57, 591 psi). Pressure of the normal 7 X 57 factory load with 11.2 gram bullet was given in Mauser’s 1908 patent boot as 3,050 atmosphere, or 43, 371 pounds.

While many Mausers in the 1908 Brazilian category will likely endure pressures considerably in excess of the 4,050 atmospheres proof loads, there might be some setback of the receiver locking shoulder with such high pressures.

Even in 1936, Phil Sharpe was warning shooters about early firearms:

There has been a great deal of improvement in steels, whether they be ordinary soft steels or various forms of nickel steel. No attempt with be made here to describe steels, as the subject would require and entire book. Thirty years ago, very little was known about heat treatment..

If you had a Winchester Model 1892 manufactured in 1905 and an identical model manufactured in 1935, assuming the original gun to be in perfect condition inside and out, you might place them side by side and notice absolutely no difference at firs glance. Careful study, however, will reveal that the later gun is manufactured better, with a minimum of tolerance, slap, looseness or whatever you may choose to call it. That, however, is the minor part of the of the whole thing. There will be little laboratory resemblance between the material of which the two gun are manufactured. Changes and improvements are being made constantly, and where changes in the quality of steel or the strengthening of certain parts through heat treatment are made, the factory rarely, if ever, makes any announcement. If these same Model 92 rifles were fired with a Magnum .38/40 load, it is quite possible that the earlier gun might go to pieces, while the later one would be perfectly safe. These facts must always be considered in handloading.

Complete Guide to Handloading by Philip B Sharpe. First Edition 1937, Chapter XXX, Magnum Handgun and Rifle Possibilities. Mr Sharpe was born in 1903, died 1961.


This post provides excellent information on the variability of Swedish M96 actions. Even though some fan boys worship Swedish actions, (a cultural memory from the days when Swedish iron was the best iron) this shows ithere is no reason to put these plain carbon receivers on a pedestal.

http://castboolits.gunloads.com/showthread.php?181256-Channeling-P-O-Mauser-blow-up-project

Variation in M96 Swede Actions

Quite a few years ago another fellow and I bought 60 of those Sweedes when they could still be had quite cheap. We decided we were going to do a quick "sporterising" on them and make a fortune. Took the whole pile and bent the bolts, drilled and tapped, cut down stocks, installed Weaver mounts, the whole banana.

Learned a lot on that one, 60 bolts to low forge and polish is one heck of a lot of work for one, not all Sweedes are heat treated the same for another.
Noticed a lot of variation when we started to drill and tap. Some seemed like butter, some hard as glass. Started to put them on the Rockwell machine and it proved out so. Some receivers would not hardly register, some were as high as 42. Bolts also were all over the place.

It didn't seem to make any difference as to year of manufacture, they just varied. Most seemed to follow the standard Mauser heat treat with a case hardening but a few came along that seemed to be hard all through.
Interesting project. I think in the long run if we would have stopped to figure our time we lost our butts. Made no difference, in our minds eye we made one heck of a killing.

http://www.practicalmachinist.com/vb/gunsmithing/input-gun-project-259589/

I have a Swedish 96 action almost blown in half.

Bolt remained locked and in position, ~ 1 sq in of right sidewall of receiver has been blown completely off, Right rail fractured right in front of rear bridge. Stock was broken in 2.

No overpressure load.. Factory..

Case failed at primer pocket.. (probably a seam in case blank)

Expanding gas has nowhere to go.. The thin wall of early Mauser actions where locking lugs must rotate, is the weak point. A couple gas relief holes (like on modern bolt rifles) Might have saved action...

Since an overpressure action failure, is not involved in ALL rifle failures. Why bother testing for action strength when the cartridge brass, as posted above, is almost always the point of failure in a rifle?? Main things to worry about are, gas/debris going to rear, and gas handling at front of action. Testing how an action handles that might be worthwhile.. Testing action failure mode with an overload of improper powder is a waste of time...

The military has experimented with, and deployed enemy caliber ammunition designed to blow up a rifle... High explosives instead of powder seem to provide a sure fire action test to failure load.. This looks pretty likely... AK-47 blows up in the hands of a terrorist - YouTube

Bad brass, Excessive (extremely) headspace. Extremely loose chamber, all cause problems

There is not an action out there, that provides ANY support for the extractor groove on a rimless cartridge.

Case base (yes fairly thick usually) has an extractor groove that is supported only by air.. Rimless cartridges of course..

Loading test rounds that exceed the strength of the weakest part, (the brass) is only going to cause the problems Speerchucker has already brought up..


The materials used in these older rifles were simple carbon steels with hardly any alloying elements and the steels of the period tended to have a lot of slag and impurtities in them.

As a comparison of material properties, keep in mind the yield strength of early receiver steels against 4140.

Inside Dieter’s book Rifle & Carbine 98: M98 Firearms of the German Army from 1898 to 1918 are the material specifications for the M98 Mauser. This is the proof: 2 round proof at 4,000 atm gas pressure, 1 atm = 14.6 psi, 4000 atm = 58, 784 psia.

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 a heat treated 1038 steel.




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


Incidentally Dieter records that at Amberg Arsenal, temperatures were judged by eye in the retort ovens used till 1905. Period Amberg bolt lugs broke at the rate of 1 per 1000 rifles!.


Post WW2 receivers are usually 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
.
Tensile Strength, Ultimate 148000 psi

Tensile Strength, Yield 132000 psi

Elongation at Break 19.0 %

I was told the following heat treatment for 4140 was too hard for firearms applications, but I am putting down for reference.

For a 1 in round AISI 4140 Steel, normalized at 870°C (1600°F), reheated to 845°C (1550°F), oil quenched, 260°C (500°F) temper, ultimate strength 270,000 psi, yield 240,000 psi, elongation at break 11%, Rockwell C53.

For decades gunsmiths and part manufacturer's have been drumming up business by making outrageous claims about the "old world craftsmanship" of these old guns, and many have believed them, but looking at the state of the art of that period, these old actions have their risks.
 
THis is all very interesting. However, a few years back Kimber was selling sporterized 1893 mausers chamber to the .308 Win. Guns were actua;ly chambr to the 7.62 NATO round in their military configuration. Kimber cut the barrels back, put them in what looked like Ramline stocks, altered the bolt handles for scope use and IIRC put a cheap scope on the guns. At least the one I handled was scoped. Further research showed Kimber had the guns proof tested to insure they were safe shooting .308 Win. ammo. They passed with flying colors.
The problem with the 93, 95 and 96 Mausers is not their structural strength but their inability to handle scaping gas should a cartridge case rupture or a blown primer occur. There is a simple fix. have a competent gunsmith mill two holes in he bottom of the bolt just like what is found on the 98 mausers and drill a hole in inr right side of the receiver ring like is found on modern sporters. The only thing you can't do is make some sort of flange ot the rear of the bolt to deflect the gas but the holes mentioned will handle most of them. The .308 is what, a 52KPSI cartridge?
I remember looking at one of those Kimbers and thinking it would make a neat truck gun but was leery of that 1893 design action. Further reseaarch brought the above info and by then I couldn't fine one to save my life.
FWIW, the 1895 is stronger than the 1893 and the 1896 Swede is the strongest of the three.
I did once have an 1893 Mauser in 7x57 that was made into a sporter by some small British gun shop. It looked just like a Rigby and was one of the sweetest handling rifles I've every owned. Been kicking myself ever since for selling it. Currently I have three rifles chambered to the 7x57 and one load that is supremely accurate in all three is 44.0 gr. of W760 for 2400 FPS at 44.500 C.U.P. according to the Winchester loading booklet I have. One of my rifles, a custom 98 Mauser with 23" barrel will put three shots into .375" and five shots into .50" consistantly provided I do my part. Brass is Winchester as is the primer and the bullet is the Hornady 175 gr. round nose. I also like the 170 gr. Sierra round nose but they're awfully hard to find since Sierra discontinued them. :(:mad: I got lucky and found a coupe of boxes at a gun show and I guard then closely.
Paul B.
 
My recollection of the Kimber rifles is a bit different.
I think they started with Swedish Mausers, 1896 and 1938 in 6.5x55.
Some they left in the original caliber with shortened barrel but Mauser steps still visible, in the plastic stocks.
Some they rebarrelled to .308, .243, and .22-250. Presumably they proof tested them in the hotter US calibers.

I once had a Carl Gustav target rifle in .308 built on an 1896 with 1912 date stamp. I had no worries about its strength, and it shot fine. I traded it off because I did not then appreciate the long heavy barrel and European idea of peep sights. Darn.
 
Thanks all. Regardless of if I re-barrel, I'll be sure to keep pressures down below 44K CUP.

Some GREAT information that was very helpful in understanding the gun and issues.

One question though: if I have a gunsmith drill the bolt/action to allow escaping gases, will this decrease overall strength at all? I was just wondering, as the design wasn't set up for those holes.

Thanks again.
 
Well, the Spaniards drilled vent holes when upgrading to the model of 1916.
I guess they thought the vent would help get gas out from a blown primer or split case better than the slight reduction in metal.
 
I'm going to bump this thread rather than starting a new one, as it touches on this subject.

I recently saw a nice m.1895 Chilean Mauser which was converted to .308. There are no markings on the rifle indicating when this modification was done. I have no knowledge of the if,when,where the Chilean government did this themselves.

My question is: Is this action strong enough to accommodate the load and pressure of .308?

Thank you.
 
I sold several of the "Kimber rebuilds" while they were being produced. My recollection is that those were built using late production Swedish 96 type actions, NOT 93/95 actions.
I'll add this as FYI.
The fact that some governments rebarrelled, rebored, or rechambered certain types of military bolt actions does not mean that those conversions were/are safe or prudent. Some were quite safe and effective but ALL were expedient solutions during time of need. If 5000 rifles were converted and 5% failed in the hands of a soldier, that was likely acceptable. In addition, many of those conversions were only meant to provide a temporary solution-not last forever.
Personally, I'd prefer a little more safety margin. I own 3-4 of the 1916 Mausers in 7.62x51 and a couple that have been rebarrelled but don't use commercial ammo in them. Only handloads at a safe pressure level go in those rifles.
 
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Keep in mind that, if a soldier's safety was desired, they wouldn't be sent into battle.

If there were rifle failures, so what ? There's always been an acceptable (to the top brass) casualty rate.



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Well, the Spaniards drilled vent holes when upgrading to the model of 1916.
I guess they thought the vent would help get gas out from a blown primer or split case better than the slight reduction in metal.
Click to expand...

Its my understanding the Spanish 1916's were rechambered for the NATO 7.62x51mm which isn't as hot as commercial .308. I had one and my gunsmith, actually a master builder told me the receiver would eventually stretch using factory 308 loads.
 
The 7.62x51 NATO and 308 Win operate in the same pressure ranges, the idea that the NATO operates at 50k PSI and the commercial load operates at 60k PSI comes only from a government manual where the "psi cup" had the "cup" dropped off in a rewrite. You cannot reliably interchange between piezo calculated PSI and copper units of pressure (CUP), but you can look at the load data for each, and see that the government load data for the 7.62x51 falls in line with the commercial 308 Win loads for the same muzzle velocities. You can't have the same powder charge and same muzzle velocities and not also have the same pressure.

And pressure is the real reason to be careful with those old Mauser bolt actions. The steel used was designed to be case hardened, and generally this was done by a "pack hardening" method which was more art than science some times. I had a gunsmith gas carbuerize a Turk K.Kale "large ring small shank" action for the basis of my 9.3x62 rifle, simply because the steel was so soft that lug setback was inevitable with any cartridge over about 48k psi.

Jimro
 
In the old days, heat treating was done by eye. It all boiled down to the experience and judgment of the craftsman to determine the "right" color to heat the steel to, for the desired result. This was not something done by apprentices, but even a master craftsman's judgment can be affected by a number of factors.

There is a story, (possibly true) that Springfield turned out a batch of bad heat treated receivers after someone cleaned decades of grime from the shop windows.

Swedish Mausers were considered the best around the turn of the century (1900) because Swedish steel was considered the best, because their ore was the best...certainly Swedish steel was better than some others, but in those early days it wasn't often clear why it was better.
 
Swedish Mausers were considered the best around the turn of the century (1900) because Swedish steel was considered the best, because their ore was the best...certainly Swedish steel was better than some others, but in those early days it wasn't often clear why it was better.
Click to expand...

Swedish iron ore was remarkably free of phosphorus. Bessemer was only able to get his process to work, because, through serendipity, he used Swedish iron. When others used different ore, his licensed process failed. He was sweating that one out, even more than President Obama is doing over his failed health care website, because if his process did not work, Bessemer was going to go personally bankrupt. It took chemistry to solve Bessemer’s problems, and that started the steel age.

http://metals.about.com/od/properties/a/A-Short-History-Of-Steel-Part-Ii.htm

Today, they understand the chemistry and thermodynamics of steel, so the starting ore is not that critical. The cultural memory remains, even if it is about as relevant as Captain Ahab hunting the white whale.
 
Amazing. I logged in to ask some questions about these rifles and the ammo. The answers are already posted! Thank you.
 
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