Steel for Action?

[shell70634]

I've decided to build a single shot drop block action. I'm still in the research phase. I would like opinions on the steel to buy. I want it to be easy to machine, accept blueing, and not unobtainium. I will have it professionally heat treated if necessary. It may be a 3/4 scale Ruger #1 since I have a few patterns in the safe. Thoughts and opinions will be appreciated.

Shelly

[samari46]

If you are gonna case harden it then use 8620 same as on the M1 Garand. If bluing then use one of the 4100 series of steels. 4130-4150. Frank

[NoZombies]

4140 PH (Pre-Hardened) is hard to beat. It machines well, and is already HT'd so you don't have to worry about it. A great many guns have been made from 4140 PH.

[EDG]

Second on the prehardened 4140.
Heat treating after machining can cost a small fortune.

[JMtoolman]

Sent you an e-mail on some 8620 that I have.

[John Taylor]

I was thinking of making a 10-22 action from steel and decided to use 12L14 and have it case hardened. The decision was made because it is the easiest to machine and plenty strong enough for the application. 8620 is used a lot for cast actions and will take color case. 4140 will probably hold more pressure but takes special care in heat treating, it can become as brittle as glass if not properly tempered. 4130 is good for hammer forging and welding but does not machine as good as I like. 4150 machines nice but I have not had a chance to machine any that was heat treated. 4140 PH is used for making rifle barrels. A little tough to machine with HSS but does nice with carbide.

[oldred]

The choice is simple really 8620 if you want color case hardening or 4140 PH if you are going to blue, 4140 PH for maximum strength also. I have built several HighWall type rifles and all have been done using 4140 PH with the first two being done using only my lathe and a home made milling attachment, I mention that to show the machinability of the 4140 PH. 4140 PH is just crazy strong and as long as you use the Pre-Hard no follow-up heat treatment is necessary, the Pre-hardened 4140 machines quite nicely using HSS with coolant. Even dry HSS can be used but go slowly or better yet just use carbide, if I didn't have carbide I would still use the 4140 PH and just spend the extra time. 4140 should NOT be color cased, I know folks have done it but they ARE trading strength off for those colors as case hardening of these alloys goes against all industry practice and recomendations. 8620 machines nicely with carbide or HSS and colors well when properly cased, it's quite strong also but with 4140 PH you have the advantage of no heat treating step with it's added expense, effort and possible warping issues plus it is quite a bit stronger to boot!

[RichardB]

I've not found heat treating from commercial companies, knowledgeable in firearms, to be expensive. Most go on weight with a minimum charge. My last treater did 4 pre 64 Model 70 receivers for $43 total, which included return shipping!

RB

[oldred]

I have not found heat treating of small items particularly expensive either (I had several small machinery parts treated before I bought my own oven) but when building that first rifle I ran into a problem that might bear consideration. I was also debating metal choices and finally settled on annealed 4140 thinking it to a better choice than the Pre-Hardened version but fortunately I checked with the local treating shop first and found they wouldn't touch it! When they were told it was for a home built gun he declined to do it, said he didn't want to take the risk, so I suppose some shops will assume it to be a liability risk since it won't be a factory firearm.

I eventually settled on the Pre-Hard 4140 and glad that I did! Sure it's somewhat harder than annealed alloy but there's more to machainability than hardness and what little difference there is between the two is not worth the hassles of having the finished receiver heat treated.

[Ballistics in Scotland]

Those are good recommendations, but there is a lot to be said for an air hardening steel, such as A2 or D2 (or possibly A-2 or D-2 in searches), which should simplify the heat treatment process. Not all of the single shot actions require heat treatment, either.

This item from my projects backlog will someday be my own small Martini in D2. I bought some pieces of D2 very cheaply on eBay from a British engineering company which had them left from an end of contract, and had the mortice cut by an electrolytic milling firm at a cost of £80. I have a more or less jewellery-size electric furnace with a 7in. maximum dimension, and I know I can heat-treat this steel myself. For some others, in thin sections, I would want to have a close-fitting temporary dummy breechblock to avoid distortion in quenching. But that would impede hardening of the inside surfaces.

220422

[shell70634]

Thank you all for the input. Does anyone have a source of supply for 4140HT in small quantities? I need a piece 1.125x2.25x4.5 And why is all I find is round stock?

[55fairlane]

Google metals supermarket....there everywhere, you can buy small lots there....

Tool steals such as 0-1 (oil hardening) w-1 (water hardening) a-1 ( air hardening) are good choices, D7 and S7 hard hard to machine.....

4140 is most found as rounds as the application is for parts mostly round such as shafting.....square stock is out there, but you must search for it, or place a special order....

Aaron

[oldred]

Speedy metals has always had everything I have needed, they have a wide selection of flats in about any size you need and will get it to you in a couple of days.

https://www.speedymetals.com/c-8316-category.aspx

They have a "Fire sale" section that often has odd&end items at less than half cost, I found a piece of 4140 PH (sometimes listed as 4140 HT both are the same) 1-1/2"x3"x6" that was perfect for one of my HighWall receivers. About the cheapest to found seems to be Ebay, several regular vendors sell various "drops" at really good prices, for example the last one I bought was piece of round stock (4140 HT) that was 4"x7" long for less than $22 shipped.

Round stock does seem to sell for a lot less than flat bar and is easier to find but then it needs to be cut end to end to make a usable flat piece, this is not nearly as hard to do as it might sound and I have done it several times using a Porta-Band saw from Harbor Freight. I had a bunch of these short bars that I had acquired as "drops" from a steel supply and for various projects that needed flat stock I cut several of these rounds this way. Just rough cut oversize with the saw then true up the surfaces on a mill or lathe with a four jaw chuck.

[oldred]

This is priced for a foot of the stuff but unless I am mistaken they will sell you less than a foot of it,

www.speedymetals.com/pc-1436-8316-1-14-x-2-14-4140-de-carb-free-heat-treated.aspx

[shell70634]

I've decided that the Ruger #1 is to complicated for me, as a beginner machinist, to tackle. So the project will be a Browning. I'm gathering drawings and dimensions and hope to begin as soon as the weather cools off. I'll make 2, one in 4140HT and the other in 8620. I'm think 32-20 and 25-20 for calibers.
225612

[oldred]

Are you planing on the classic model 1885 Winchester (not to be confused with the later Jap built Browning/Winchesters) or that original Browning Single Shot like in your illustration above? My first project was originally meant to be a copy of Browning's original Single Shot rifles but I decided to just build Winchester's version instead, several reasons for this but the biggest problem was lack of info and a total lack of any kind of detailed drawings and only sketchy dimensions. After searching and a few phone calls I became convinced that no usable drawings exist for these rifles and without an actual example of one of these very rare guns to work from it was just too impractical to even hope to get a reasonably close copy of one. Besides that I have been told by people familiar with them that of the relative handful in existence, all hand-built by John and his brothers in the early 1880's in Ogden Utah, almost all of them are somewhat different with some being significantly different than others.

Winchester's version based on the early design and sold as the model 1885 is a MUCH improved version over the fairly crude rifles originally built by the Brownings before selling the design to Winchester and not only are good examples easy to find but detailed drawings can easily be found even on Ebay for only about $20 or so!

Just a note about the drawings, it's been said quite a bit on various forums that the available drawings (all seem to be based on the same one) have serious omissions and errors that make them extremely frustrating to use and can lead to serious machining mistakes. I have worked with an Ebay version of these prints quite a bit while helping a buddy with his project and just recently had these prints given to me by him after he lost interest in the project, I can say with confidence that the rumors of omissions and flaws are way overblown! I honestly have no idea of what omissions they are speaking of since these prints appear complete right down to the smallest screws and springs including every detail, if anything is left out it must be unimportant because we never found anything at all! As far as errors we did find one and it seems to be the one that started the complaints, it seems if the receiver is built exactly to the drawing specs the breech block linkage will go over-center causing the block to fall back slightly after closing causing loose headspacing. The common reason given for the error is that the sear pin hole is located wrong and causes serious difficulties getting it right, this is NOT the case! The only error we could find is that the "ears" on the action lever are shown a few thousandths too long and angled slightly wrong, these problems are very easily corrected as long as the builder is aware before making that lever. I strongly suspect that some failed projects that blamed errors in the plans were not errors there at all but mistakes in either reading the prints or machining errors incorrectly blamed on the drawings or a combination of both.

[shell70634]

Oldred,
Looked on ebay and found a bunch of posters and art. Can you get more specific so my search would be narrower? Or could I buy a copy from you.

Shelly

[shell70634]

Nevermind Oldred. Had someone help me shop and found it. Guess I don't shop enuff on the computer

[oldred]

Are you talking about the 1885 HighWall drawings that can be found on Ebay? If so that's the set I was talking about and except for that one error, easily fixed however, I think you will find those drawings to be very complete, very detailed and quite clear and sharp. The set I have is both the actual drawings received by my friend from the Ebay seller and the much larger copies he had made at a local printing shop. Although the drawings as they arrive are quite usable as they are the full "blue-print" size copies are easier to work with and printing service places like Staples, etc can enlarge them for you, not absolutely necessary I suppose but still much nicer to work from!

Also too I just noticed that 1885 HighWall raw castings are available on Ebay again for $175, they are from the same seller that had them a few weeks ago I believe and the last time he listed them they all sold out in just a few hours!

[shell70634]

Yup, found em on ebay. Ordered a set. I'll get copies made to work from. I learned not to allow the originals in the shop. I spill lotsa coffee. I've heard about the castings but this project is more of a personal challenge. I've got a good lathe and I'm cleaning and renovating my mill and will use these projects to learn on. I've got a retired machinist who's offered to help when I get stuck. I've got a chunk of 4140HT and a piece of 8620 from some great people on this forum. Just gathering info and materials til retirement in January 2019. Then I hope to have more time to devote to my looooong list of projects.

[oldred]

IMHO you are definitely making the right choice using bar/flat stock rather than starting with a casting, getting that 4140 stock to the point of where the casting would be at the start of the project is the easy part. After that I honestly believe that working with your raw stock will be much easier than working with the casting because setup will be a LOT easier! Those castings would probably be easier and quicker if a person had the production setup jigs but without them setup would be the major portion of the work and besides any serious mistake (mistakes do sometimes happen unfortunately) can quickly turn a fairly expensive receiver casting into a paperweight! Having to start over with raw stock might be disappointing but it would be much less expensive, of course to be fair finishing the exterior contours of the casting would be simpler and would require a LOT less shaping and file/stoning work. That exterior finishing however is the most fun part for me and I don't consider that work at all, seeing it take shape under the files is very satisfying and goes a lot faster than most folks might imagine, in fact I was very surprised at how quickly the first one I did took on it's final shape.

However you decide on each step please keep us posted, for a long time I have wanted to see other builders get involved and I think it would be a lot of fun if we could get several folks together to share info and to discuss problems that might arise or help with the inevitable "head scratching" episodes that are surely going to arise. I have built three of these from scratch and currently working on a fourth but each time some new puzzle presents itself and has to be solved so if I can be of any help at all please feel free to PM me or just post it here.

[john.k]

Ive found its easiest to start the machining with the block mortice....once this is square or whatever it needs to be,its much easier to match the block size,and its also much easier to machine the externals square with the internals. ...Obviously if I was an accurate worker this wouldnt matter,but I aint.,so I just go with the flow.......not so much a gun as a work of art.

[oldred]

Ive found its easiest to start the machining with the block mortice....once this is square or whatever it needs to be,its much easier to match the block size,and its also much easier to machine the externals square with the internals. ...Obviously if I was an accurate worker this wouldnt matter,but I aint.,so I just go with the flow.......not so much a gun as a work of art.

Couldn't agree more about that block and mortise as I too cut the mortise first but before doing anything I first mill the receiver blank on one side, the top and what is to be the front all flat and squared to each other. These surfaces are then ALWAYS used as reference and setup surfaces, I then establish a center-line (referenced from the flat squared sides) both top and bottom along the length and vertically on the front end 90 deg surface. As long as a person works from the same side and maintains those reference lines getting lost will not be a problem, trying to just start at one random machined point and then locate everything else relative to that makes it too easy to lose reference. By machining not only the breech block mortise first but also the lower tang area, etc it's much easier to get a really good fit. I know that theoretically starting with the small parts first shouldn't be a problem with fit but tiny errors can occur especially for those of us who can't lay claim to being pros and fitting the attaching parts to the finished receiver is a lot easier than the other way around!

[Willbird]

One point of order, while 4140HT is pretty strong, it may not have the same properties as an action heat treated to the ideal hardness. I have tested a few rem 700 actions I had when I had access to a rockwell hardness tester and 36-38 sounds like about what I got. So if you duplicated a rem 700 from 4140HT which is 28-32 rockwell C it would not have the same properties as the action you copied, it might still be plenty strong though.


Received the results of the Rockwell test and the action was in the 36-37 HRc range and the bolt was in the 41-42 HRc. So I will not find out if the remainder of the bolt will separate or not?

Note the difference in hardness between the two parts of the action, that is on purpose too, running the same metal at the same hardness together will wear more than if one part is harder than the other.

I have also seen a lot of 4140HT parts that were scrapped due to cracks in the bar stock, some of them BIG parts 24" in diameter and 24" long....cracks found after about 30 hours of machine work :-). Gunsmith friend made up some 1911 compensators from 4140HT and after he had them finished and blued he saw the crack that probably ran through the whole bar of material.

Just a few things to be wary of....those things are not material specific....for something you are going to put a LOT of time into, buying an aerospace grade of material with certifications might be worth some extra cost.

Bill

[oldred]

One point of order, while 4140HT is pretty strong, it may not have the same properties as an action heat treated to the ideal hardness. I have tested a few rem 700 actions I had when I had access to a rockwell hardness tester and 36-38 sounds like about what I got. So if you duplicated a rem 700 from 4140HT which is 28-32 rockwell C it would not have the same properties as the action you copied, it might still be plenty strong though.



Note the difference in hardness between the two parts of the action, that is on purpose too, running the same metal at the same hardness together will wear more than if one part is harder than the other.

I have also seen a lot of 4140HT parts that were scrapped due to cracks in the bar stock, some of them BIG parts 24" in diameter and 24" long....cracks found after about 30 hours of machine work :-). Gunsmith friend made up some 1911 compensators from 4140HT and after he had them finished and blued he saw the crack that probably ran through the whole bar of material.

Just a few things to be wary of....those things are not material specific....for something you are going to put a LOT of time into, buying an aerospace grade of material with certifications might be worth some extra cost.

Bill

All very good points and buying certified material certainly offers peace of mind if it's worth the added cost to the builder. A finished receiver made from 4140 will be fairly easy to check for any cracking however voids or inclusions are a bit more of a problem, I think checking for cracks after machining is complete and a rather hefty proof testing step should render a home built firearm about as safe as we are going to get them. However I still want to err on the side of safety and while I pressure tested my rifles (except for the WMR 22) at approximately 50,000+ PSI as indicated by loading data I still limit my loads to around 25,000 to 28,000 PSI. If I were building a modern design rifle for high pressure cartridges I would want to use steel that has been certified but obtaining such materials in small quantities can be a bit pricey for what we are doing, still if a high pressure cartridge is wanted/needed then maybe it should be considered regardless.

[Willbird]

All very good points and buying certified material certainly offers peace of mind if it's worth the added cost to the builder. A finished receiver made from 4140 will be fairly easy to check for any cracking however voids or inclusions are a bit more of a problem, I think checking for cracks after machining is complete and a rather hefty proof testing step should render a home built firearm about as safe as we are going to get them. However I still want to err on the side of safety and while I pressure tested my rifles (except for the WMR 22) at approximately 50,000+ PSI as indicated by loading data I still limit my loads to around 25,000 to 28,000 PSI. If I were building a modern design rifle for high pressure cartridges I would want to use steel that has been certified but obtaining such materials in small quantities can be a bit pricey for what we are doing, still if a high pressure cartridge is wanted/needed then maybe it should be considered regardless.

Really tough stuff to machine without cnc and flood coolant, but one prior employer made some parts out of Inconel 100 (we actually used aeromet 100...same stuff more or less) because it was as strong as machined as 6150 that was machined and heat treated post machining. Might be OK home shop machining for simple parts. The SFM for an HSS drill was something like 18-20 SFM...watching a 3/4" drill loaf along at that speed was amusing :-).

The stuff is still pretty much as strong at 1000F as it is at room temperature too :-).

S7 might be an ideal steel if you had a way to have it heat treated in a controlled atmosphere furnace.

Kinda wonder if boiling a part like happens in bluing, or warming it to that temp then cold bluing it might make cracks visible ?? I have used the spray bomb crack detection stuff before, it works fairly well.

Bill

[fast ronnie]

I am kind of late to this thread, but here is my two cents worth.
4130 or 4140 will warp during heat treat. A2 and D2 are both thru hardening steels that are designed for cutting. When heat-treated they will have the same hardness all the way through, and as such will have no warning of failure. They will not tolerate shock very well. S7 might be a reasonable material to work with, as it is designed for heavy shock loads. There is a better grade of steel for this purpose, however. 4340 is somewhat similar to to 4140, is easy to machine, is very strong and shock resistant. It warps very little during heat-treat compared to similar grades of steel (4130 and 4140) and and when heat-treated to approximately 40 rockwell, has a great strength along with just enough "give".
It is used in making high-performance crankshafts. Those things take an awful lot of torsional flexing. It is one of my "go to" steels for anything requiring high strength and has some really good properties. It is not hard to find, as you can order it from Mcmaster Carr or several other suppliers. It is only very slightly more expensive than 4140. There is not a single reason that I can think of not to use it.

[oldred]

I have about 250 lbs of Inconel 718 in 4"x8"x18" blocks and I think it will come in really useful someday for an anchor if I ever get around to buying a boat, Lol!


Joking aside I have the stuff and simply don't know what to do with it, I know a few things I would like to make with it but about the only thing I have actually made so far using my manual machines is a big pile of dulled and/or broken cutters.:shock: I mean that's some tough stuff! I can get started cutting Ok it seems but then all of a sudden it will work harden and after that even carbide can't handle it but then so far all I have done is just play around with it to see what it was like, not much to like I suppose.

[oldred]

4130 or 4140 will warp during heat treat.


That's what's so nice about 4140PH it machines quite well as is, for a rifle receiver it is very strong and needs no further heat treating. I am sure there are other alloy steels out there that fill the bill just as well but 4140 seems perfect for this, a good combination of hardness and incredible strength plus good machining characteristics also, maybe not the best of any alloy but still very well suited for the home rifle builder. Also as noted earlier by several others it is the alloy of choice for Shiloh's rifle receivers and unless I am mistaken even the Ruger no 1.

[John Taylor]

Fun stuff to work with is Titanium. I have rifled about a dozen barrel made of this stuff and it is the only time I have had smoke coming out of the bore of a barrel in the rifling machine.

[Willbird]

I have about 250 lbs of Inconel 718 in 4"x8"x18" blocks and I think it will come in really useful someday for an anchor if I ever get around to buying a boat, Lol!


Joking aside I have the stuff and simply don't know what to do with it, I know a few things I would like to make with it but about the only thing I have actually made so far using my manual machines is a big pile of dulled and/or broken cutters.:shock: I mean that's some tough stuff! I can get started cutting Ok it seems but then all of a sudden it will work harden and after that even carbide can't handle it but then so far all I have done is just play around with it to see what it was like, not much to like I suppose.

If you use the Machinery Handbook speeds and feeds, and use flood coolant I have run the same 3/4 HSS steel twist drill for days running the machine 24 hours a day (two 12 hour shifts)....use a power feed of about .01" per revolution.

As far as S7 goes, where it excels is the Jominy Notch test.....which tests how a steel does under impact when a deep cut stress riser is present. Lots of gun designs include stress risers in their design.

The strongest attribute for 4140 is that it blues really nice :-). ...it is not bad by any means, but it has nothing on S7 heat treated then hit with some nice ion nitride :-).

[oldred]

Lots of gun designs include stress risers in their design.

Just a note about that and any falling block design such as the High wall and Low wall designs, when cutting the Breech block mortise be aware that the inside corners need to have a small radius to eliminate stress risers at that point in the receiver to prevent receiver failure in this highly stressed area. Then there is that extractor notch in the chamber that has lead to disastrous failures when cut using sharp tools and no radius is left in the corners of the cut, that one can be critical especially with higher pressure rounds but even moderate pressures may cause failures.

[kywoodwrkr]

"be aware that the inside corners need to have a small radius to eliminate stress risers at that point in the receiver to prevent receiver failure in this highly stressed area"
oldred,
What radius is ideal, or a range for radius?
I'm going to try and use an EDM for machining and wire in it is .010" dia., compensation wise that is considered .006 with electrical gap.
Therefore my smallest radius would be .006, larger would just be drawn in as fillet.
Cutting outside of breech block not a problem, 0.000 to, reasonable.
Thanks.

[oldred]

What radius is ideal, or a range for radius?

The print calls for a .015 radius of the inside corners of mortise.

I started to reply with this info last night but rather than just take it from memory I decided I would wait and post a shot of the actual print his morning, wouldn't you know there was an oil stain on the large version in that area and I couldn't get a satisfactory shot of the original small print. Both are clearly readable when looking at them but when transferred to the computer neither was clear enough, at least to me but I can try again if you want. In any case it is .015 for certain.