Quick question: How to tell a hammer forged barrel?

[David Hoback]

Well I can offer some evidence to it Dusty...I actually AM a metallurgical expert. A topic I’ve devoted a great deal of time to for over a decade! CHF is simply another way of rifling. There is no supporting evidence that shows it to last any longer or give any better accuracy. That’s not to say it gives worse either, mind you. I have nothing against it. Barrels made via CHF in the US are typically very, very good. FN, Daniel Defense & and a few months names... Although I credit this to them using high quality material, and top class machining techniques. We are talking about high quality US companies doing this after all. On the flip side, as I’ve already stated, EVERY Romanian AK47 barrel was made via CHF. But now we are talking about a Com-block country, during the Cold War, using questionable steel(at best), by anyone who could operate the machine! Do they last forever? Well, yeah....CHROME LINING tends to do that! But go watch some full auto mag dump tests on You Tube. (There are plenty of ‘em.) They fail at approximately the same rate that button rifled barrels WITH CHROME LINING do! And do we even need to go over the accuracy of the Romy’s? LOL!

Buss word? Well, in a way. It’s what companies do. See, everything was already there. The “Myth” & “legend” surrounding Forged Japanese Samurai swords. All the AR15 manufacturers had to do, was jump transfer that myth & legend over to CHF barrels. While they were at it, they tagged on a few bucks to every CHF barrel & BAM! Instant success.

 

[MistWolf]

Back in the day, Remington did not advertise that the barrels of their 700s were cold hammer forged. Back then, it was believed that CHF barrels were less accurate because of stresses from the forging process. It was said that as the barrel heated up, the stresses would cause the barrel to warp. Yet the 700s of that time had a reputation for precision.

Germany used CHF to turn out a high number of barrels fast and cheap during World War II.

The biggest reason I never bought a CHF barrel for my AR is because the sellers charge a premium price for what should be an economy barrel.

 

[Skylerbone]

it was believed that CHF barrels were less accurate because of stresses from the forging process.

Indeed the process adds residual stresses which must be addressed after. If done correctly, and assuming good steel and process to begin with, the tangible benefit of CHF barrels is consistency and an extremely smooth bore. If you’ve ever owned a hand-lapped barrel (Anschutz for example) and have looked through a bore scope you’ll see the lack of chatter marks, just as you will in a CHF. That translates to a cleaner shooting barrel as well.

For a long range AR build CHF or polygonal would be desirable for the above traits but then I wouldn’t likely recommend the typical AR barrel manufacturers for that (DD for example).

 

[Varminterror]

I actually AM a metallurgical expert.

I have never met a qualified/certified metallurgy expert or materials engineering expert who would have called themselves a “metallurgical expert.”

 

[cdb1]

I have never met a qualified/certified metallurgy expert or materials engineering expert who would have called themselves a “metallurgical expert.”

View attachment 946169

My first thought was along the same line. Just about every self proclaimed expert I’ve ever met was anything but.

 

[David Hoback]

Indeed the process adds residual stresses which must be addressed after. If done correctly, and assuming good steel and process to begin with, the tangible benefit of CHF barrels is consistency and an extremely smooth bore. If you’ve ever owned a hand-lapped barrel (Anschutz for example) and have looked through a bore scope you’ll see the lack of chatter marks, just as you will in a CHF. That translates to a cleaner shooting barrel as well.

For a long range AR build CHF or polygonal would be desirable for the above traits but then I wouldn’t likely recommend the typical AR barrel manufacturers for that (DD for example).

I’m sorry Skylerbone, but Im gonna have to disagree with pretty much all of that, because it’s simply not true. These LIES about CHF have only come about in the last decade or so(not by you..., but by people trying to SELL something to the unlearned). Apparently you haven't been reading all the posts. I and several others have pointed out evidence to the point. The Hammer Forged barrel process was introduced & developed by Germany during WW2 as CHEAP & QUICK means of processing barrels. It had nothing to do with accuracy. Almost ALL AKs use CHF barrels, and “long range Accuracy” is not synonymous with them! Over the last 100yrs, not a single major Long range award has been won by a competitor using a CHF barrel, as NONE of the top barrel manufacturers do CHF barrels. Ask High Power competitors what they use in their ARs. You’ll find nearly every one uses CUT Or Button rifling. Bartlein, Krieger, Lilja, Broughton, Pacnor, Douglass, etc, etc.... This is what you will find. And what every expert will recommend in a long range build.

 

[lysanderxiii]

Back in the day, Remington did not advertise that the barrels of their 700s were cold hammer forged. Back then, it was believed that CHF barrels were less accurate because of stresses from the forging process. It was said that as the barrel heated up, the stresses would cause the barrel to warp. Yet the 700s of that time had a reputation for precision.

Back in the day, and today, that can be true, rotary forging leaves extremely high internal stresses in the barrel after forging, and if not properly stress relieved, this will result in warping.

What many people overlook is that button rifling also leaves high residual stresses that can lead to problems if not properly stress relieved.

 

[David Hoback]

Back in the day, and today, that can be true, rotary forging leaves extremely high internal stresses in the barrel after forging, and if not properly stress relieved, this will result in warping.

What many people overlook is that button rifling also leaves high residual stresses that can lead to problems if not properly stress relieved.

Correct. The button rifling is in fact a type of “forging”. The button, typically made of Tungsten Carbide, has. Negative of the rifling pattern, and is displacing the metal as it is drawn through the blank. Any time pressure is used to displace or move the material, it is forged!

 

[lysanderxiii]

(quote)Rotary Swaging Precision Gun Barrels, Prepared for Rock Island Arsenal:

"Precision cold forging of barrels by either rotary swaging or radial forging is the most recent trend in barrel manufacturing procedures in the United States and has been adopted in other nations. The utility of this barrel fabrication technique has been amply demonstrated for conventional weapons in terms of precision and cost, but there are inherent problems with this procedure which could affect the quality and stability of barrels required for accurate performance. Because these problems are common to other well developed technologies, information is available for defining an effort for solution of these problems which arise mainly from residual stress gradients and process design parameters affecting complete fill of the mandrel form. Understanding of the source of these problems and how they are affected by tool design and fabrication procedures would provide a quantitative basis for process design for improved quality and accuracy and a significant advancement in barrel technology.

"A brief review is provided in the following to describe the problems associated with the manufacture of precision barrels to justify the approach taken in this program. In this context, conventional fabrication implies the use of either broaching or button rifling, recognizing that broaching is becoming less significant. Furthermore, button rifling is becoming secondary to cold forging for commercial and military barrel manufacture. However, relatively little is currently known about the effects of processing variables on the quality of the cold forged product and what alternatives in the fabrication sequence exist to improve and insure quality features when a particular requirement exists. . . . The dimensional precision provided by precision swaging depends on the precision of the starting blank and the alignment of guide bushings and dies. Typically, some manufacturers of these barrel fabrication machines will guarantee ±0.0002 inch on bore dimensions with straightness equal to or better than the straightness of the starting blank for production fabrication . . . .

The major advantages of precision rotary swaging over broaching and button rifling are fabrication economy, precision, surface finish and relative ease in producing the rifling in materials of high hardness. However, a major disadvantage is the severe magnitude and gradients of residual stress which exist throughout a swaged barrel. This condition results in a straightness dependence on asymmetry of the OD contour, an unknown response of the system to pressure during firing, and a general instability of the rifled blank during final machining. These problems have been observed during commercial barrel manufacture where bore contractions as large as 0.0013 inch were observed in the finished product. . . .

Galling of the workpiece to the mandrel and residual stress are two major problems with swaged barrels which have significantly affected fabrication costs. Both of these problems have not been well publicized. Galling results from process design parameters which produce a large length of contact of the die and workpiece and may precede complete fill of the mandrel form to produce good rifling. Galling occurs predominantly in the steps or sides of the lands and occasionally in the very center of the land and results in serious degradation of the land form. . . . Attempts to [eliminate galling] have resulted in swaged barrels with "rounded" corners from using a maximum reduction sufficient to avoid galling while still producing a nearly complete rifling form. . . . For a right hand twist galling will occur first on the left side of the rifling (viewed from the breech) where the amount of fill will be greater than the right side. Air gage measurements will not distinguish [incomplete fill] from perfect rifling and it is not uncommon to find excellent [diametrical] dimensional precision with the incompletely filled form . . . . Because the corners of the incompletely formed land are free formed, control of their height and width is difficult.

Extremely precise dimensions for rifling are obtained in a very narrow range of machine adjustments, chambering of barrels after rifling requires a good knowledge of the forging process and considerable working experience.
(end quote)

In short, CHF and rotary swaging are not magic. Good results come from good techniques and care and precision in all stages of manufacture, and poor techniques, poor preparation, and careless work will result in a poor product, just like any other manufacturing endeavor, including cut, broached and button rifled barrel manufacture.

The major advantage in CHF and rotatry swaging is speed, cost, and reduced manpower (especially skilled manpower).

By the way, no M61 Vulcan, 20mm, 25mm GAU-12, or 30mm GAU-8 barrel is CHF/rotary swagged. They all use cut rifling, think about that and why that might be.

 

[JFrank]

Will all the real experts please raise their hands, I’m confused

 

[Poper]

Please correct me if I am in error, but it would seem to me, the quality of a hammer forged barrel will be most dependent on:
1) quality of the barrel steel blank;
2) quality and precision of the machine(s);
3) quality and precision of the mandrel.
4) stress relieving methodology / quality

I have multiple Tikka and Sako rifles with CHF barrels. Every one will shoot sub MOA with its preferred load.
Special ? No, not on its surface, but they are much easier and quicker to get the bore clean than say my Savage or custom button rifled barrels from Shilen and McGowan.

JMHO, YMMV, of course.

 

[Skylerbone]

I’m sorry Skylerbone, but Im gonna have to disagree with pretty much all of that, because it’s simply not true. These LIES about CHF have only come about in the last decade or so(not by you..., but by people trying to SELL something to the unlearned). Apparently you haven't been reading all the posts. I and several others have pointed out evidence to the point. The Hammer Forged barrel process was introduced & developed by Germany during WW2 as CHEAP & QUICK means of processing barrels. It had nothing to do with accuracy. Almost ALL AKs use CHF barrels, and “long range Accuracy” is not synonymous with them! Over the last 100yrs, not a single major Long range award has been won by a competitor using a CHF barrel, as NONE of the top barrel manufacturers do CHF barrels. Ask High Power competitors what they use in their ARs. You’ll find nearly every one uses CUT Or Button rifling. Bartlein, Krieger, Lilja, Broughton, Pacnor, Douglass, etc, etc.... This is what you will find. And what every expert will recommend in a long range build.

Well...you are a “metallurgical expert” and you said this:

I actually AM a metallurgical expert. A topic I’ve devoted a great deal of time to for over a decade! CHF is simply another way of rifling. There is no supporting evidence that shows it to last any longer or give any better accuracy. That’s not to say it gives worse either, mind you.

So which is it? In your expert opinion, formulated over many, many, many years; can CHF produce an accurate barrel or not? I made no claim about breaking records, merely asserted that if a manufacturer used good material, controlled process, and relieved stress properly the result should be an accurate barrel that is easy to clean (increasing consistency over a typical AR barrel with machining marks, button chatter, etc).

Did you misrepresent yourself as an expert or did you misrepresent the accuracy potential of CHF in your post? What else, based on your metallurgical expertise, do you take issue with in my post? You said “almost everything”, could you bullet point for me and lay down some knowledge?

 

[MistWolf]

Back in the day, and today, that can be true, rotary forging leaves extremely high internal stresses in the barrel after forging, and if not properly stress relieved, this will result in warping.

What many people overlook is that button rifling also leaves high residual stresses that can lead to problems if not properly stress relieved.

Button rifling also got its share of criticism for that very reason.

 

[lysanderxiii]

Please correct me if I am in error, but it would seem to me, the quality of a hammer forged barrel will be most dependent on:
1) quality of the barrel steel blank;
2) quality and precision of the machine(s);
3) quality and precision of the mandrel.
4) stress relieving methodology / quality

I have multiple Tikka and Sako rifles with CHF barrels. Every one will shoot sub MOA with its preferred load.
Special ? No, not on its surface, but they are much easier and quicker to get the bore clean than say my Savage or custom button rifled barrels from Shilen and McGowan.

JMHO, YMMV, of course.

Close.

1) quality and skill of the personnel setting up the equipment,
2) quality of the barrel steel blank,
3) quality and precision of the machine(s),
4) quality and precision of the mandrel, and
5) stress relieving methodology/quality.

Incidentally, these are the same things that the quality on a button, or cut rifle barrel rest on.

 

[David Hoback]

I've already explained the point...multiple times. Look at the barrel maker, NOT the rifling technique. I’m trying to figure out where you think I’ve cross talked? Nothing I can say will change your mind. It wasn’t for you. But if you’d like, go study for a few days...a week, month, whatever. Then ask me any question related to metallurgy you’d like to. I’ve said this before....I only speak on subjects I KNOW.

You said for a long range AR build. CHF or Polygonal rifling is desirable. My dispute & evidence to is NONE of the top barrel makers using this technique, nor any top LONG RANGE competitor. But if I’m mistaken on how your post reads, I apologize. I do stand by what I’ve said about the barrels.

 

[JFrank]

Well someone could reach out to the “real experts” Here’s a couple ....

Carson Lilja - Lilja Barrels
Stan Taylor - Douglas Barrels
Frank - Bartelin Barrels

 

[mcb]

Have we covered this part, I have not read all the replies: Go back to the inception of the rotary/cold hammer forging of gun barrels. The Germans developed it in the run up to WWII as a way to make gun barrels faster and last longer for one of the ultimate barrel burners the MG42. It worked hammer forged barrels out lasted other barrel manufacturing processes of the time (late 30's into the 40's) using the alloys available at the time and could be manufactured in less time than the other methods. These barrel came off the machine requiring minimal addition machining to make the finished barrel. The barrels had chamber, rifling, and exterior profiling complete coming off the CHF , needing only the ends addressed. For this application CHF was a big benefit for the use and available alloys.

But with today far more advanced alloys and more advanced heat treating methods and understandings and the fact that we are not trying to crank them out as absolute as fast as possible for a gun that is firing at upwards of 1300 rpm and to support a war effort the benefits of CHF are not as great. As others have already pointed out for modern firearms any of the three conventional methods can produce exceptional barrels assuming skilled people, running well maintain equipment, using quality materials. As for life span at the rate of fire most of us are going to be shooting our firearms, the cost of ammo will dwarf the cost of gun barrels so pick the one that shoots best and let the barrel life fall out as it may.

Some interesting if slightly dated reading.

https://apps.dtic.mil/dtic/tr/fulltext/u2/a021752.pdf
https://apps.dtic.mil/dtic/tr/fulltext/u2/a136159.pdf

 

[Varminterror]

1) quality and skill of the personnel setting up the equipment,

This was the glaring omission I noticed when reading @poper’s list.

Give all of the right gear and materials to the wrong crew and they won’t even produce something which could be called a barrel. Given skilled set up, great results can be achieved at a low variable cost.

It’s not so challenging to build a sub-moa rifle as many folks seem to believe. There’s no mystery to it, and pretending it requires advanced training or uncommon knowledge is disingenuous. CHF, CL, draw button, push button, cut... it’s not so complicated if you aren’t chasing the rabbit. Some last longer than others, and some shoot smaller than others when you ARE chasing, but for most folks, the difference is nil.

 

[David Hoback]

Well someone could reach out to the “real experts” Here’s a couple ....

Carson Lilja - Lilja Barrels
Stan Taylor - Douglas Barrels
Frank - Bartelin Barrels

Frank actually replies fairly often over at Savage Shooters. My current build uses a Shilen Match, because well...the price was simply too good to pass! And in all honesty, Tbe vast majority of shooters(myself included), will not see a discernible accuracy difference among the premium barrels. But my next rebarrel will be a Bartlein. We actually have been having this very discussion on SavageShooters. A member asked which barrel is the best. Looking through shooting history, several of the top barrel makers have held the crown among the best. Shilen, Broughton, Brux, Krieger, McGovern, etc., etc... For anyone interested, it’s a good thread with a lot of info. Many, Gunsmith rifle builders(like me) & precision long range shooters there speaking up. https://www.savageshooters.com/showthread.php?67487-Highest-quality-aftermarket-Savage-replacement-barrels

In the end, any premium barrel is going to perform exceptionally well, provided
it has the supporting criteria. Simply sticking a premium barrel onto a rifle will not magically transform it into some lights out shooter. For instance, my bench gun was a full custom build from a stripped action. With my worked up reloads, it’s a SUB 1/2MOA rig...or better.. But going with a different barrel, at this stage of the game, would not instantly make it a SUB 1/4” Rig!

Pick your liking. BTW... to show that I don’t have any bias towards CHF, here is actually another barrel I was considering. Though it was not for the CHF aspect on its own. In the end, I decided the Ballistic Advantage was the better choice. But for any CHF fans, this is a great barrel at a decent price. https://blackrifledepot.com/apoc-armory-16-223-wylde-cold-hammer-forged-barrel/

 

[Poper]

This was the glaring omission I noticed when reading @poper’s list.

Give all of the right gear and materials to the wrong crew and they won’t even produce something which could be called a barrel. Given skilled set up, great results can be achieved at a low variable cost.

It’s not so challenging to build a sub-moa rifle as many folks seem to believe. There’s no mystery to it, and pretending it requires advanced training or uncommon knowledge is disingenuous. CHF, CL, draw button, push button, cut... it’s not so complicated if you aren’t chasing the rabbit. Some last longer than others, and some shoot smaller than others when you ARE chasing, but for most folks, the difference is nil.

I stand humbly corrected.
Of course the quality and skill of personnel at all aspects of the design, fabrication, assembly, tuning and load development are important to every firearm and will contribute (or not) to the accuracy of a firearm.

Both Sako and Tikka firearms are produced by the same company, marketed by the same company and are produced for different price points. Neither the Sako nor the Tikka are considered top drawer target rifles, though they are both known for excellent accuracy at their price points. The Sako is generally more finely finished and has slightly different features that define its higher price point. I own both in 6.5x55 SM (Sako 85 and Tikka T3 Hunter) and I have found their accuracy potentials are nearly equal / very similar.

I am not a benchrest competitior, but I do compete in Highpower and Smallbore Silhouette where the minute differences in the highest quality barrels probably do not matter nor may be measured. Still, it would seem reasonable to me that any barrel mfr. that is producing the highest quality units, in addition to the qualities noted above, will also need to pay very close attention to the wear tolerances of his production equipment and tools and will require replacing cutters/buttons/mandrels/etc. rather frequently in order to maintain such a high level of quality. Once again, I may be in error!

I am not a machinist nor a metallurgist. I am only an architect and shooting/handloading hobbyist so my opinions and perspective are worth everything paid for them.

 

[JFrank]

Personally I don’t know a Darn thing about making a Barrel or Metallurgy but I do know a few heavy hitters that like and try several different barrel companies, also keep a rack of barrels

 

[lysanderxiii]

Have we covered this part, I have not read all the replies: Go back to the inception of the rotary/cold hammer forging of gun barrels. The Germans developed it in the run up to WWII as a way to make gun barrels faster and last longer for one of the ultimate barrel burners the MG42. It worked hammer forged barrels out lasted other barrel manufacturing processes of the time (late 30's into the 40's) using the alloys available at the time and could be manufactured in less time than the other methods. These barrel came off the machine requiring minimal addition machining to make the finished barrel. The barrels had chamber, rifling, and exterior profiling complete coming off the CHF , needing only the ends addressed. For this application CHF was a big benefit for the use and available alloys.

But with today far more advanced alloys and more advanced heat treating methods and understandings and the fact that we are not trying to crank them out as absolute as fast as possible for a gun that is firing at upwards of 1300 rpm and to support a war effort the benefits of CHF are not as great. As others have already pointed out for modern firearms any of the three conventional methods can produce exceptional barrels assuming skilled people, running well maintain equipment, using quality materials. As for life span at the rate of fire most of us are going to be shooting our firearms, the cost of ammo will dwarf the cost of gun barrels so pick the one that shoots best and let the barrel life fall out as it may.

Some interesting if slightly dated reading.

https://apps.dtic.mil/dtic/tr/fulltext/u2/a021752.pdf
https://apps.dtic.mil/dtic/tr/fulltext/u2/a136159.pdf

[BOLD] Sorry, no.

From the abstract of the second report you linked to (ADA136159 - Cold Rotary Forging of a Thin Walled Rifled Barrel):

[In a report]. . . on cold rotary forging of rifling into a thinwall gun tube, it was stated that the yield strength of the forged material increased in the longitudinal direction, while a recoverable loss was observed in the tangential (hoop) direction.

(my emphasis).

The rotary forged barrel is not stronger in the direction of importance for a barrel (hoop). The lost hoop strength can be recovered through stress relieving, but it only brings the barrel back to its original level, with the gains in the longitudinal directions also returning to its original level.

Neither of the two reports note any increase in wear characteristics. In fact, there is a more recent report, specifically comparing a rotary forged M4 barrel to a button rifled M4 barrel, using the exact same barrel steel.

The results showed that for the same 41V50 steel, there was no difference in the wear life of the barrels, as measured by a bore erosion gage. And, when measuring the average dispersion of the groups fired the CHF barrels reached the rejection limit of 7" at 100 yards almost 1500 rounds before the standard M4 barrel.

ADE403315 - M4 Carbine Forged Barrel Study Report, Foltz & Escalona, Picatinny Arsenal, 2011

EDIT:
The Germans developed rotary forging to quickly produce acceptable barrels with less manpower at a faster rate. They were never "better" nor did they "last longer" than standard barrels, and 70 years worth of technical reports on the subject agree with that assessment.

 

[lysanderxiii]

Below is a graph of the average throat erosion of M4 carbines. Thirteen M4s with 41V50 barrels made by Colt are shown in the blue-square line and thirteen M4 barrels with 41V50 barrels made by hammer forging are shown in the yellow-triangle lines. The zero line is the maximum reject dimension for throat erosion for the M4. You will note that the two lines are right on top of each other until 8,200 rounds. (EDIT - the violet-square and X-light blue lines are for different steels, so are not pertinent to this discussion.)



The graph below is the average dispersion of those same thirteen barrels, and the red line at 7.00 denotes the maximum allowable dispersion for the M4 Carbine. It actually looks more like 1,800 rounds earlier.

 

[R_P_K]

I don’t know about others, but the finish pattern on the HF barrel blanks photo listed above looks neat to me - I can see that in the raw in SS with a nice action and a nice composite stock.

I remember when the ruger target .22s were left like that