4130 / 4140 Tubing For Barrels?
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  1. #1
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    Default 4130 / 4140 Tubing For Barrels?

    Hi:

    As we probably all know in this forum, the biggest single challenge to manufacturing a barrel in the regular machine shop is the deep-hole drilling part. This usually requires specialized equipment or a highly modified lathe. After you get the hole drilled and finish reamed, the rifling part can be as simple as driving a carbide rifling button through the bore with a hydraulic jack.

    Looking around on-line, I noted the existence of thick-walled mechanical tubing in alloys that are suited to making rifle barrels, like 4130 (suitable enough for many applications, as I understand it) or 4140 (one of the standard barrel steels).

    The great majority of this tubing does not have anywhere near the appropriate bore diameter down the middle or correct wall thickness, but there are a FEW places in the catalog of a FEW vendors where you get some pretty good combinations of ID and OD...For my purposes, sourcing 4130 tubing with an OD of 1" and an ID of .250 is fairly easy...I am thinking that this should be about the perfect diameter to finish-ream out to around .264 for a 6.5mm barrel. 1" would be a little thinner than desired at the breech end, but I was thinking about a tightly fitted collar there to build up the ID around the chamber and for threading to match an action. There are other viable tubing/caliber combinations available, but this is the primary one I am interested in for the moment.

    And before I get shouted down, allow me to stipulate the following:

    Yes, this is not the way proper barrels are done.

    Yes, we are talking about steel that is not rated for use as rifle barrels (though, for whatever it is worth, there are Chinese vendors selling 4140 tubing specifically to be used to make DIY rifle and pistol barrels).

    Yes, I can buy a Green Mountain basic gunsmiths blank for the same money, already rifled and probably of better quality than I could ever manage to make.

    Yes, I would have to be sure to end up with some very conservative thicknesses around the bore as a partial safeguard to a barrel bursting on ignition.

    For all of that, I am still interested in doing this.

    So, what say you?

    Thanks in advance:

    -Tom

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    Depends on how that tubing is manufatured.

    Any welded seams are a failure waiting to happen, I think, unless you were playing only in the Black Powder or similar lower pressure areas.

    IIRC, it was said that the commonly available .22 cal barrel liners are aircraft tubing that has been button rifled.

    Me, I'd rather ream out a barrel and start from there, if I were not looking to go whole hog into gun drilling.

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    Quote Originally Posted by bullet308 View Post
    Hi:

    As we probably all know in this forum, the biggest single challenge to manufacturing a barrel in the regular machine

    Looking around on-line, I noted the existence of thick-walled mechanical tubing in alloys that are suited to making rifle barrels, like 4130 (suitable enough for many applications, as I understand it) or 4140 (one of the standard barrel steels).

    For all of that, I am still interested in doing this.

    So, what say you?

    Thanks in advance:

    -Tom
    Tubing is so full of stress, and unless the highest grade, it could have defects that might kill you or someone near by.

    Second hand barrels are inexpensive. Get one that is shot out for a song, and "recalibre" it as a first effort.

    What you don't know should never be found out with a weapon.

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    I doubt the .250 hole would be very straight.

    When the Springfield Arsenal made blanks into barrels they inspected after every operation for inclusions. Those found with inclusions on the surface were scrapped. Sometimes the inclusions were still beneath the surface after the last operation and the barrels split/blew up under proof. And from reading the old literature it doesn't appear that was a rare event.

    Sleeving the chamber end is probably not good either. I can't recall any barrel makers that do that for high powered rifles.

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    Ive used drawn and swaged hydraulic tube for both liners and shotgun barrels.This type of tube is solid drawn,and every length is proof tested.....one size I use is proofed to 10,000 psi.Every length.And internally is ironed with a swage for a brilliant mirror finish....the surface is also very hard and tough,but the tube is low carbon ,and not directly hardenable.

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    I never understand why so many guys want to make their own (probably vastly inferior) gun barrels, with no where near the required equipment when they can be purchased in almost unlimited variation so relatively cheap?

    Well unless you are in a POW camp.

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    In addition, button rifled barrels are pulled not just pushed through and have a bearing that allows the carbide button to rotate creating the twist as it is pulled.

    And where are you going to get that carbide button all ground to size with the proper twist?

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    Buttons are available. Shot out .224" barrels should be readily available and would be better stock. But buttoning a profiled barrel will give inconsistent rifling depth because of the differing thickness of the metal at any given point. Cut rifling would be more appropriate for this kind of material.

    While 10,000 psi sounds like a lot, it is really shotgun strength, not centerfire rifle strength. The readily available tubing has a weld seam that has been ironed flat with a mandrel (DOM--drawn over mandrel) to give it a smooth bore. Seamless tubing is made but it is even less straight than DOM tubing and not as smooth.


    Why does anyone want to make a barrel? Why does anyone want to make anything for himself? So he can say he did. It's not about the economics.

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    Quote Originally Posted by GGaskill View Post
    Buttons are available.
    Where?

    Quote Originally Posted by GGaskill View Post
    Why does anyone want to make a barrel? Why does anyone want to make anything for himself? So he can say he did. It's not about the economics.
    Oh I get that, but it is usually by guys that have little to no experience in the basics like fitting and chambering a barrel or making from scratch other gun parts, yet want to make the leap to making a precision, high pressure barrel, on the cheap w/o any of the needed equipment.

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    very true on the psi rating 50,000 psi isn't out of the question
    in 223.

    never mind that the hardest part of making a good barrel is getting the right size hole
    and straight, neither of these things is found in dom tube.

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    Quote Originally Posted by 72bwhite View Post
    very true on the psi rating 50,000 psi isn't out of the question
    in 223.
    Many modern cartridges develop about 60,000 psi. A barrel blank should be rated AT LEAST to 90,000psi to give a little bitof a safety margin.

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    Where?

    Here is one place: Banggood rifling buttons.

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    Lilja does deep hole drilling. Give him a call and see what he wants for a bar with a hole in it. It'll be straight, and ...

    ... actually made from an appropriate piece of material.

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    Quote Originally Posted by wesg View Post
    Lilja does deep hole drilling. Give him a call and see what he wants for a bar with a hole in it. It'll be straight, and ...

    ... actually made from an appropriate piece of material.
    Good luck, I stopped by Lilja and they had no interest in drilling 4140 annealed for 10-20 bolt action receiver blanks for me.
    So I am gathering up bits and pieces to fab up a gundrilling setup for my lathe.

    But all this academic, I doubt our 2 post OP has any real interest or drive to make his own barrel....... probably just dreaming.

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    Quote Originally Posted by CalG View Post
    What you don't know should never be found out with a weapon.
    Amen brother.
    CarlBoyd

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    Quote Originally Posted by Doug W View Post

    But all this academic, I doubt our 2 post OP has any real interest or drive to make his own barrel....... probably just dreaming.

    Ah, I assure you, I am (or at least was) quite serious. The thing that is dissuading me at this point is that the mechanical tubing available is not entirely trustworthy for this application, and a bit of difficult-to-detect carbon crud in a seam within the steel could lead to a really nasty failure that I want no part of. I have seen what that looks like (a batch of substandard steel got turned into M14NM barrels back in the early '90s by one of the bigger players of the day, and they blowed up REAL good, fortunately, not on a gun I built), and nope, I choose not to play. I just wanted to see if anybody here knew something I didn't (which many here do, but not in this particular domain).

    Oh, that, and the economics are not very good, either. As it is, I just ordered a cheap 6.5mm blank from Sarco for a project for $40, which is roughly what the tubing would cost before the various reamers and buttons, and I still have a Shilen .308 blank stuck back, plus a small pile of various takeoffs.

    If somehow I could get ahold of steel certified for this application, I might try it at some point, but then, that stuff would no doubt cost me more than mechanical tubing, assuming it were readily available.


    Thanks for all the feedback.

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    G.Gaskill mentions that a profiled blank will have varying groove depth if buttoned.....Interestingly,this is part of the Marlin Microgroove patent,which claims a tapered rifling depth resulting from a carefully dimensioned outer profile.The patent is long expired,so you can try this yourself.

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    Quote Originally Posted by bullet308 View Post
    Ah, I assure you, I am (or at least was) quite serious.

    Oh, that, and the economics are not very good, either. As it is, I just ordered a cheap 6.5mm blank from Sarco for a project for $40, which is roughly what the tubing would cost before the various reamers and buttons, and I still have a Shilen .308 blank stuck back, plus a small pile of various takeoffs.

    If somehow I could get ahold of steel certified for this application, I might try it at some point, but then, that stuff would no doubt cost me more than mechanical tubing, assuming it were readily available.
    So after considering the economics, the effort and the equipment and you have decided to buy a rifled blank instead of making your own.

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    Quote Originally Posted by Doug W View Post
    So after considering the economics, the effort and the equipment and you have decided to buy a rifled blank instead of making your own.
    Pretty much. It is still something I might play with pistol calibers at a fraction of the pressure, but was going to do a centerfire rifle barrel and that is a bridge too far, unless I am desperate. I could do it, but not safe enough to suit me. I ended up buying blanks, yes. I have read most of the relevant materials available about how to make barrels via different methods, but previously I had priced buttons from US makers and they were cost-prohibitive for my little projects. Then, I saw the Chinese, Russian and Ukrainian buttons that are now available for fairly small money, and I thought the idea warranted another look. I might give it another look again at some point if conditions change, but for now, I will focus on chambering and fitting other people's blanks, as I have in the past.

    The only reason I brought the question here is that I figured that if anybody knew how to make this work out, it would probably somebody on this list, and I found virtually nothing yay or neigh on the topic with searches, so...I asked. :-)

    And again, thanks.

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    Quote Originally Posted by bullet308 View Post
    Pretty much. It is still something I might play with pistol calibers at a fraction of the pressure, but was going to do a centerfire rifle barrel and that is a bridge too far, unless I am desperate.
    That is the conclusion most of us have discovered.

    I bought and read Harold Hoffman's book The Modern Rifle Barrel 30 years ago and saw that making your own barrels was imPRACTICAL, as in Practical Machinist and economically unviable.
    And that was way before the barrel making competition drove down prices to a Green Mountain barrel blank, for, well, accounting for inflation,,, practically free. LOL

    Plus the thought of pumping 15 gpm in my shop waiting for an oily disaster is more than I can bear.


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