Barrels and how to buy them

My opinions for what they may be worth.
For a hunting rifle, pre-threaded, short chambered (or long chambered) barrels can work out just fine but are really intended for the hobbyist rather than the professional 'smith. Most gunsmiths prefer to showcase their abilities and the prechambered blank takes some of this away from them.
Stress relieving after turning is like fixing the fence after the cows have escaped. A blank which is improperly stress releived or not stress releived at all will, in all likelyhood, warp when it is turned. When this happens, all the stress relieving in the world will not straighten it out. Cryogenic treatment (still not shown to have the stress releiving capability of heat) certainly won't. If the warped barrel is mechanically straightened, stress relieving afterwards will minimize stresses introduced by staightening.
Contouring a barrel does not introduce stress into the material. It only removes it along with the material removed. An exception might be where tooling is very dull so that the chip load is unnecessarily high. When a barrel blank warps in turning, it is because the stress has been removed from one side of the blank by material removal. Heat treatment at this point will do little or nothing to change the shape of the barrel but will eliminate remaining stresses within the material.
I have found hammer forged barrels to be remarkably stress free. Whether this is due to the resulting random grain structure of the steel or the fact that the blank comes out of the operation smokin' hot and is stress relived as a result, I can't really say. I can say that I have turned down a lot of hammer forged barrels with no noticable warpage or dimensional change. Conversely, I have contoured some cut rifled barrels which threatened to crawl out of the lathe on their own! When I find the barrels from a particular maker to be problematic when contouring, I will never use that maker's barrels again since it is apparent that stress releiving was incomplete or not done at all.
The Lothar Walther brochures I have indicate that most of their barrels they sell to the trade are button rifled. The Lothar Walther people do seem to be legends in their own minds but the product does appear to be equal to most others at least. Their particular brand of stainless is much tougher (and tougher to machine) than any used by most makers. It is claimed to offer significantly greater barrel life and anecdotal evidence supports this but I've not seen any results of an independent comparison. Regards, Bill.
 
mysticplayer said:
...Hammer forging stress free????? That has got to be the worse way to make a barrel stress free. I just think that beating a piece of metal into submission can't be good for its grain structure. Yes, they can make decent barrels but BR quality???? Doubt it...

Jerry
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My 0.2 cents! Not very familiar with barrel manufacturing, but forged and cold rolled bolts and screws are way superior to any cut ones. As a mater of fact, in aerospace and automotive industry forged and cold rolled fasteners are mandatory due to their superior strength and resistance to fatigue. This is a result of dense and uninterrupted crystal structure/grain formed by forging and cold rolling that follows the contour of the metal part. As for forged barrel “walking” when warms up, that’s different animal; however I’ve seen statements that it could be cured successfully by cryogenic treatment prior to contour machining. Also, cryogenic treatment could fix already finished rifle if it has tendency to “walk”. As for the BR quality; looks like that barrels cut by the hook have the edge over others. The question is; how many of us need ¼ MOA rifle with several pounds barrel. Competition and varmint hunting with bipods; OK. For everything else, “thanks, no thanks”. 1.5-2 MOA, weighing 7-8 lb with scope will do it.
 
Chrome vanadium is a tougher material than chrome moly
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When you say "tougher", what does this mean?

I have found hammer forged barrels to be remarkably stress free.
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Bill, which brands have you used?

And what about the quality of the steel itself? If it is 4140, then does it matter where it is from? Or can the material still have that designation and have enough other materials in it to provide an advantage/disadvantage? In other words: Is all 4140 close enough to each other as to be considered the same?
 
4140 is an AISI designation, referring to composition - specifically percentages of alloying components. No's prefixed with a 2 are nickel alloyed steel, 31-32-33 is Ni-Chr, 41 is Chr-Mo, 43 is Chr-Ni-Mo, etc. The standard is followed by various mills, but is not neccessarily certified for pedigree.
4140 is a medium carbon steel, and as such is affected (benefitted) by heat treatment - typically quenching and tempering. This introduces another variable, as degree of heat treatment, and forming procedure affect strength. Example - hot rolled 4140 tensile strength - 89 ksi, cold drawn - 102 ksi.
All of these steels used for modern rifle barrels are strong and tough compared to mild steel, typically 20 -50 % stronger. Given the magnitude of the chamber stresses during firing, its easy to understand why - even the relatively low pressure Lee Enfield rings in at 70 ksi!
As mentioned previously, forging is generally considered to be benificial to component strength. Aside from grain structure, the surfaces are left in a state of compression, which mitigates crack propagation. Of course, stress relieving would diminish this potential benefit - so one would have to rely upon the inherent impact resistance (toughness) of the metal.

Reference for most of the above - Design of Machine Elements M.F. Spotts 1971
 
Leeper said:
A blank which is improperly stress relieved or not stress relieved at all will, in all likelyhood, warp when it is turned. When this happens, all the stress relieving in the world will not straighten it out.

Contouring a barrel does not introduce stress into the material. It only removes it along with the material removed. When a barrel blank warps in turning, it is because the stress has been removed from one side of the blank by material removal.

I have found hammer forged barrels to be remarkably stress free. I can say that I have turned down a lot of hammer forged barrels with no noticable warpage or dimensional change. Conversely, I have contoured some cut rifled barrels which threatened to crawl out of the lathe on their own! When I find the barrels from a particular maker to be problematic when contouring, I will never use that maker's barrels again since it is apparent that stress releiving was incomplete or not done at all.

Regards, Bill.
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My experience has been the very same as Bill's. (Quoted above).

You can not tell if a barrel needs to be stress relieved until you try turning it. Back in 1969 I had a couple of P.O. Ackley barrels I was trying to turn down, On each very light cut the barrel would warp in a different direction. After a lot of wasted time and a phone call to Ackley the barrels were thrown away and Ackley replaced them with properly stress relieved barrels. That was the last time I used a P.O. Ackley barrel.

I have turned all sorts of Remington barrels lighter (some very light) and never had a problem with any of them. All of Remington's barrels are hammer forged.

Dennis
 
Someone earlier commented on the desireablity of cold rolled barrrels; personally I would avoid them like the plagque. During cold rolling it is my impression that all sorts of stresses are left in the surface of the barrel and should you then contour the barrel, it has been my experience that it will warp terribly. I have never had that experience with a barrel that had been milled or turned on the outside and presumably been stress relieved at some point along the way.

cheers mooncoon
 
mooncoon said:
Someone earlier commented on the desireablity of cold rolled barrrels; personally I would avoid them like the plagque. During cold rolling it is my impression that all sorts of stresses are left in the surface of the barrel and should you then contour the barrel, it has been my experience that it will warp terribly. I have never had that experience with a barrel that had been milled or turned on the outside and presumably been stress relieved at some point along the way.

cheers mooncoon
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I do not think any rifle barrels are made of "cold rolled steel". Steel that has the capability to be cold rolled is not the correct composition for heat treating.

Often the steel for making barrel blanks is hot rolled to cylindrical dimension. If the steel is not hot enough during this rolling process cracks can form on the outside of the blank and that blank is useless as a barrel.

All barrel steel requires stress relieving before being shipped to the gunsmith.
 

I do not think any rifle barrels are made of "cold rolled steel". Steel that has the capability to be cold rolled is not the correct composition for heat treating.
All barrel steel requires stress relieving before being shipped to the gunsmith.[/quote]

I am thinking of two barrels in particular that were octagon blanks and came from Numrich arms quite a few years ago. One I turned to 1/2 octagon and the other a friend and skilled machinist and gunsmith turned to 1/2 octagon. They warped very badly from stress and neither heated significantly during the turning. Neither showed any indication of milling marks on the surface nor scale and I can only presume they were cold rolled.
They are the only barrels that I have had that did warp noticeably.

cheers mooncoon
 
mooncoon said:

I do not think any rifle barrels are made of "cold rolled steel". Steel that has the capability to be cold rolled is not the correct composition for heat treating.
All barrel steel requires stress relieving before being shipped to the gunsmith.
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I am thinking of two barrels in particular that were octagon blanks and came from Numrich arms quite a few years ago. One I turned to 1/2 octagon and the other a friend and skilled machinist and gunsmith turned to 1/2 octagon. They warped very badly from stress and neither heated significantly during the turning. Neither showed any indication of milling marks on the surface nor scale and I can only presume they were cold rolled.
They are the only barrels that I have had that did warp noticeably.

cheers mooncoon[/quote]

I believe what you experienced was caused by a failure of the manufacturer to properly stress relieve the barrel. Nothing to do at all with the turning you did. A properly stress relieved barrel will not warp as you take successive light cuts off it. I have turned full blanks down to very light barrels and they stayed straight and true due to proper heat treating and stress relieving. None of this really matters - buy a quality barrel - none of the makers are deliberately making bad barrels.
 
We turn 420 stainless at work and I used to turn 316 stainless at the last place I worked. I have found that you need to use a lower speed/feed combo. than the CM steels (4140) and a lot lower than the straight carbon steels (1045).

I tend to think that the stainless is a little more dense (closed pore) giving you better corrosion resistance and better finish even though it doesn't measure up to the others in hardness. It does resist pitting rather well.

Ripstop
 
1899 asked what hammer forged barrels I've used. I have worked with cylindrical blanks from Swiss Arms, H-K, and Winchester. As well, I have recontoured barrels from Remington, Winchester, and Steyr. In all cases, the barrels remained as straight as they were at the start of the operation and there was no apparent internal dimensional change.
I experienced the same sort of problem Dennis described when I used some Bauska barrels. They warped all over. I finally just put them in the oven and ran it through the self cleaning cycle a couple times. This was not enough heat to achieve a proper job of stress relief but it made the barrels at least possible to turn. These barrels were not 4140 but were a carbon- manganese alloy as I recall. Not nice to work with and, like Dennis with his Ackley barrels, my use of that maker's barrels was ended.
 
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