Action Rockwell Hardness

[John P.]

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.

 

[bruce moulds]

i remember years ago the advice was not to touch a bbk with a long bargepole.
bruce.

 

[USMA84DAB]

I would absolutely like to see your results!

 

[Hogpatrol]

Please post the results. Be interesting to see which ones are the most soft. My guess is the older ones.

 

[bruce moulds]

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

 

[mdwest]

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

I’m a Mauser?

 

[John P.]

i remember years ago the advice was not to touch a bbk with a long bargepole.
bruce.

Yes the early Korean made BBK actions were undesirables. The later ones marketed by Olympic Arms were properly heat treated. I have one of the later ones, still un-barreled. It is reserved for a 450 Ackley, I have the barrel, chamber reamer, dies and cases. A back burner project.

 

[John P.]

Well my thread over on the site turned into a compost pile. Usual behavior for those guys.

So I deleted my posts there.

I will post here over the next few days for your gents that have a true interest.

 

[Boyd Brooks]

Have you ever tested Dumoulin or Zastava’s mauser style actions?

 

[John P.]

Readings taken under the lower lucking lug, as Douglas Barrels used to do in the 1970's when they tested actions prior to installing barrels.

Columbian M98. 23 on the Rockwell C scale.

Santa Barbara 1951 Corona M98, 20 on the Rockwell C scale.

A very old Pre 64 Winchester action with the small wing safety. 38 on the Rockwell C scale.

Post 64 Winchester Classic. 47 on the Rockwell C scale.

Ruger M77 Tang safety. 49 on the Rockwell C scale.

Ahh the much cussed BBK action. This one is a late model, sold by Olympic Arms (The "Ultra Mag" action) and is properly heat treated. 34 on the Rockwell C scale.

Bolt from the post 64 Win M70. 44 on the Rockwell C scale.

The tester. It is a beast, weighs 200 pounds. Good old American made iron.

This one made in World War II. An everlasting design, they do not wear out.

I will test more this weekend. Several CZ Mark 10 actions, a couple of Whitworths, a Pre 64 Win from the 1950's, a Mexican Mauser. Several Enfields and whatever I can find in the shop.

Nope, do not have a Dumoulin.

 

[HuntingGold]

I am completely unfamiliar with what is good or bad with regard hardness in action types. Can someone educate me a little? I'm thanking you in advance.
Randy

 

[gbflyer]

Very interesting discussion. Thank you for taking the time to do this.

 

[fourfive8]

I am completely unfamiliar with what is good or bad with regard hardness in action types. Can someone educate me a little? I'm thanking you in advance.
Randy

^^ 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.

 

[John P.]

I am completely unfamiliar with what is good or bad with regard hardness in action types. Can someone educate me a little? I'm thanking you in advance.
Randy

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.]

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!

 

[HuntingGold]

@fourfive8 and @John P.
I thank you both for your posts. I'm not a rocket scientist by any means but have taken a few classes. My inner gut was telling me that a high number may not be the best thing as the steel could become brittle and a low number could be so soft as to allow a rupture. It's nice to know my inner gut was leading me the right direction. I look forward to following this thread.

Of particular interest to me is that the bbk action was mentioned that earlier actions were different than those manufactured later. I'm currently looking at buying a custom built rifle on the bbk-02. The trouble I'm having is determining who actually built the rifle and when. From my research the engraver passed away in 1999 therefore it was built prior to then, but that's the best I have.

Again, thank you both for the education and I will continue to follow along.
RH

 

[John P.]

Investment cast receivers as the M77 Ruger and others can suffer from lack of impeccable detail at the time of casting. Proper mold design, sprue geometry for good flow, correct melt temperature for good flow into the mold and I am sure many other things may contribute to a poor casting. Hopefully the cast receivers are tested by X Ray or another method in insuring their suitability.

I am not an expert in receivers and hardness & the metals used. I am just having fun with the hardness tester and reporting my results. Wish I had purchased the Rockwell tester many years ago! Bought this one about a month ago.

 

[John P.]

Hunting Gold, if the action was from Olympic Arms in Tacoma it likely is a good one.

I think the most complaints about the BBK are about the finish. They were investment cast and not polished, so the gun builder had a lot of finish work to do.

Find someone with a hardness tester near you and test the area beneath the bottom lug.

I never found out if Olympic Arms imported the "Ultra Mag" from South Korea or if they cast them in house or had a US Foundry cast them. There is a large foundry in Seattle capable of doing the work and they have been in business for decades. Sadly Olympic Arms went out of business many years ago. I do recall seeing a photo of receivers in the raw on a bench waiting to be machined in their facility in Tacoma.

 

[HuntingGold]

Again, thank you. I'm learning here today.

 

[Hunter4752001]

Many years ago I had a mate who was a metallurgist. Poor bastard used to tear his hair out listening to us lay people talk about steel 'hardness' and 'strength'. Thereupon would frequently follow hours of lectures about what the terms actually meant. In a nutshell (to us struggling lay people):
Hardness relates to the materials relative resistance to penetration.
Toughness is the ability to absorb energy and deform without fracturing. Highly desirable if you want to avoid bit of steel embedded in your face.
Strength is the maximum amount of stress the steel can withstand without exceeding the limits of elastic deformation. ie being able to return to original size.
As can be deduced, hardness isn't of great value except for wear resistance. What an action needs is toughness and strength. Modern chrome-molly alloys are often chosen for actions specifically because they rate highly for strength and toughness.