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What I have a question on is the issue of what limits the CUP: chamber or action?
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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/magazin...159partial.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/show...low-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...roject-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
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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.