Action Rockwell Hardness

[Hogpatrol]

Modern chrome-molly alloys are often chosen for actions specifically because they rate highly for strength and toughness.

Can add machinability and weight to that equation.

 

[John P.]

And you can adjust the tensile strength of alloy steels by manipulating the hardness. Thus the requirements for heat treating in the modern machine shops.

 

[BC.Pat]

Thanks for posting, a very very interesting topic.
regards
Pat

 

[nztimb]

An interesting topic to follow with thanks for the insightfull questions thata have bought some easily understood answers to the table. It is no wonder this is the best site on the internet bar none.

 

[fourfive8]

458, I have a 36 Mexican. Put it on the tester last week and got low readings. Tested it in three places. I will test it again this weekend.

PS we both were posting at the same time, I will merge both posts and print and put in my notes. Good info you put in your post!

Thanks! appreciate it. Always been curious about that action. I wouldn't doubt the pressure of that destructive test of the Mexican Mauser may have exceeded 100,000 psi. Even now, after looking at various burst chambers and actions, it remains a mystery to me why that action/chamber didn't burst. I currently load for an older Loewe Chilean Mauser, so have an interest in all such info on these older actions.

The other day, I was looking at some of the alloys, trace elements and heat treatments of the steels used for actions and mercy!! the complexity of describing or predicting the parameters of the relative "strength" potentials among them is overwhelming! Way beyond my level.

 

[Stompbox]

Thank you for the information.

 

[DG Gunsmith]

Very interesting, Mate...

 

[Ray B]

I'm sending a PM regarding the possibility of checking the hardness of the barrels on my 1910 Rigby double rifle. I'm wondering how the Rockwell scale compares to the Vicker scale.

 

[fourfive8]

Here's a link to a site that has a comparison calculator and tables for some of the scales

Steel Hardness Conversion Table

Steel hardness conversion chart: Shows equivalents using Brinell, Rockwell B and C and Vickers scales. These values are approximate and for guidance only. Also hardness ranges for heat treated steel

www.steelexpress.co.uk

 

[John P.]

Finally finished up the big machining projects and ran a couple of actions across the Rockwell tester today.

1936 Mexican. Hmmm. 17 on the Rockwell C scale.

Mark X (CZ) Whitworth. 53 on the Rockwell C scale. Should be a strong action if it is 4140 as rumored.

 

[Bob Nelson 35Whelen]

I have been running Rockwell Hardness Testing on various actions (M98, M70, Ruger 77, BBK).
The results are very interesting. Any interest here? I will be running more tests over the weekend.


View attachment 381153View attachment 381154

@John P
Very interested especially in older rifles like the M17's and P14s and comparisons between old ones new models like the pre 64, post 64 and new Winchester and savages.
Bob

 

[Bob Nelson 35Whelen]

^^ Best question/comment in this whole thread.

I looked over in the Acc Rel forum where this all started and seemed to be too many experts over there. A good study is that of the history of the 1903 Springfield action (both Springfield and RIA) as it pertained to serial numbers/dates of manufacture and the hardening issues those actions evolved through. It would be worth the time to look at that history. Hatcher's Notebook has quite a bit of info about it.

Best hardening for an action seems to me to be a lot more complex than simply a measurement of hardness. That engineering science at any depth is well above my mastery and level of understanding for sure. Basically what I gather is that some steels can be so hard as to become brittle. While an action that is considered modern and very hard, if the basic yield strength is exceeded, it can become a fragmenting grenade. Conversely, a relatively softer action may fail and yield to pressure or stress that exceeds yield strength, chances are better it won't become a fragmenting grenade. It may simply deform or rupture but not fragment. Some actions are soft enough to deform from the cumulative effects of repetitive stress. These literally incrementally yield to the point of becoming unusable but never really catastrophically fail. While a "soft" action may be deemed unworthy of modern loads or consideration, it may still be very safe... in effect "giving" instead of fracturing with explosive effect. The word on the street for example and I have no reason to doubt it is that many old forged Mauser actions are somewhat "soft". Some of these deform or wear out over time. It's also my understanding many Mauser actions have case hardened skins to resist friction wear while maintaining their resilience or as some say "toughness" by not being too hard (brittle) internally. Which is which within the "Mauser" group I have no idea.

One time I had an expendable, old, small ring, (Mexican IIRC) Mauser in 7x57. I loaded it with a case full of Bullseye, topped with a 175 gr bullet. On top of that I poured another 1 oz of #6 lead shot. I ran a small piece of tissue down the bore to keep the shot charge in contact with the bullet. I placed it horizontally in a disposable wooden vice and set behind a dirt berm along with a video camera to record the event. I remotely fired it. I was expecting a split chamber and action and sheared lugs with the bolt blowing out of the action. Nope! The sound was a very loud, sharp crack. The stock was splintered and split longitudinally in several places. The magazine was swelled and the floorplate was blown off the bottom of the action, the extractor was blown off the bolt and out of the action, the bolt was set back between 3/8-1/2" and there was no case left save a coating of sintered brass plating around the bolt head and that part of the action. I believe a member here one time did a similar test on an old pre-64 Winchester 70 that yielded similar results.

I do know that certain modern cast receivers can be considered brittle and can fragment like a grenade- even though they are modern and rate very high in strength (hardness). I saw a video, a few years ago, of a destructive test of one of the high power T/C single shots. Round was loaded with excessive charge of fast powder along with placing a bore obstruction just ahead of cartridge- the cast action and chamber part of the barrel fragmented.

I believe the complete understanding of the metallurgy of firearms actions is extremely complex and only fully understood by relatively few scientists and engineers.

@fourfive8
I've seen a similar thing done with an SMLE No1 mk111. The damage was remarkable considering. Magazine blown out, bottom metal severely bent wood splintered but the amazing thing the bolt didn't shatter and the locking lugs held. The bolt head was about a half inch from the face or the barrel and bent like a banana. We had a good chuckle and urban only comment was thank God we didn't hold on to that to touch it off.
Bob

 

[Bob Nelson 35Whelen]

mausers are soft on the inside and hard on the outside i believe.
bruce.

@bruce moulds
Sounds like me mate as well as cute and loveable.
Bob

 

[Bob Nelson 35Whelen]

20 to 22 on the Mausers is common but considered low for high pressure large cartridges, although they have been used for many years for all types of powerful cartridges. Mausers have lived on their exceptional design for over a century. Design sometimes trumps tensile strength (directly proportional to hardness) in a successful action. Hold the pressures below 50,000 psi in the mid size cartridges (like 8mm or 30-06) and I feel safe in using the rifles. I am a bit uneasy with the cartridges like 7mm Mag, 300 Mags, etc., loaded up to the 60.000 psi range.

The mid 30 to 40 range on the Rockwell C with a modern alloy like 4140 is much safer for the "hot" cartridges.

50 and above is in knife hardness range, I think too hard. Recall the low number Springfields that were glass hard and subject to failure.

I was surprised at the high number on the M77 Ruger.

My problem with old Mausers is the steel. Almost impossible to determine what was used. I have read "a medium carbon steel". Questions are does the case hardening the actions went through do anything to heat treat the inner material? Only way to find out is to section a receiver and test, but this still does not tell us much as we do not know what alloy to compare the readings to.

The case hardening on the Mausers is thin, and I believe the preload placed on the diamond penetrator will penetrate the case hardening and correctly read the underlying metal. The Rockwell tester applies a lighter pre load first to penetrate surface irregularities then a heavier main load is applied. Anyway I have 2 98's not suitable for building rifles, some time in the near future I plan on sectioning the receivers for internal testing.

@John P
Wouldn't it also depend on the steel types, you mentioned carbon steel but what about chrome moly and stainless steels as well as the nickel steels.
Bob

 

[ducmarc]

Wonder where the Japanese type 99 and 38 land.was always told they were real hard.i have always favored a used action in good shape over brand new. I figure every old action has been proof tested by somebody's reload.to me everything got cheap by the 60itys . Atleast till the 90itys.seems things are better now but still not sure about anything cast.

 

[ducmarc]

When I worked in an automotive machine shop we had a cheap hardness tester for grinding crankshafts.was a tube with a ball bearing in it and a scale.if I remember right we would throw out detroit cranks below 60 Rockwell if we ground through the hardness.