Hammer Forged AR barrels

[Rokman]

I would like to know what a cold hammer forged barrel is and what makes it superior to a button rifled barrel? I am going to purchase a new AR barrel and have noticed some of the more expensive barrels list hammer forging.

 

[briansmithwins]

Cold hammer forging is a way of making barrels cheaply in large quantities.

Those barrels can be better or worse than button cut barrels. It all depends on the manufacturer and their standards.

Cold hammer forged barrels can be stronger than cut barrels as the forging process changes the grain of the steel. They can also be made with very fine interior finishes. BSW

 

[Rokman]

I was looking at a couple of internet vendors that had close-out Daniels Defense barrels and they had new hammer forged Daniels Defense barrels, and the new ones were much more pricey. I have read that hammer forged barrels can last longer.

 

[dfariswheel]

A short description of hammer forging barrels:

A mandrel with reverse rifling is put inside a hollow steel thick wall tube.
Rotary hammers rotate around the tube, hammering the outside of the tube against the mandrel.
As the tube is hammered, it is compressed onto the mandrel and grows longer as the metal is hammered thinner.

Once the hammering process is done, the mandrel is extracted from the tube.
What you have is a work-hardened barrel with rifling on the inside.

Hammer forging is a fast way of making barrels, and when done right the barrels can be high quality.
Like with all other barreling processes, the quality depends on the machines and workmanship of the makers.
The finished barrel can be excellent or poorly made.

The fact that a barrel is hammer forged is no guarantee of a good, accurate barrel.

 

[MCMXI]

The strength of cold worked steel parts is due to the MASSIVE increase in the number of dislocations within the part as a result of cold working and has little to do with the change in grain shape. Grain boundary density doesn't change appreciably with cold working. Dislocations within the atomic structure of the steel severely limit the movement of atomic planes of atoms which greatly increases the force required for elastic/plastic deformation. Deformation of steel can only occur if planes of atoms are able to "slip". If their motion is hindered by dislocations then it takes a lot more force to overcome the dislocations. Precipitation hardening has a similar effect on elastic/plastic deformation. Precipitates within the alloy hinder the movement of atomic planes.

 

[Rokman]

Thanks guys. Wow, 1858, you are way too smart. I have several AR carbines/rifles and none of them are hammer forged and probably never missed it. I think I will just buy an ordinary button rifled barrel at a good price.

 

[Z-Michigan]

Read this article:

http://technology.calumet.purdue.edu/met/higley/NotesOnHammerForgedBarrels.pdf

Long and short, hammer forging is faster and cheaper for the manufacturer, and may be more durable for the user. The higher price in AR barrels is hilarious since it is a cheaper process and in most other types of rifle it dominates but is not considered remarkable.

Prediction: in 5-10 years nearly all AR barrels will be hammer forged, and sell for about the same price (inflation adjusted) as button rifled barrels sell for today.

 

[Maverick223]

Hammer forged barrels do tend to be stronger, but due to the internal stresses from beating the crap out of it, it also tends to have slightly inferior accuracy (when compared to good button/cut rifled barrels). For most users the difference in accuracy or durability is not likely to be noticeable much less significant.

 

[OhioChief]

Well 1858, it just depends on how cold your talking about. Drop it to ablsolute zero for 24 hours, and you're talking about a whole different outcome....although I wouldn't suggest hitting it with a hammer at that temp....or putting your tongue on it.

 

[Maverick223]

Drop it to ablsolute zero for 24 hours

...and exactly how do you go about doing that?

 

[dfariswheel]

The reason hammer forged barrels cost more is because of the horrendous cost of the hammer forging equipment.

The barrel maker has to recover the high cost of the investment.

 

[Z-Michigan]

The reason hammer forged barrels cost more is because of the horrendous cost of the hammer forging equipment.
The barrel maker has to recover the high cost of the investment.

True for small fish, but Remington, Ruger, etc. already have the equipment and use it to its fullest, so their barrels are quite inexpensive. All Ruger barrels have been hammer forged for decades now, for instance. And I've read somewhere that a Remington 700 factory barrel (which is hammer forged) is only a $60-80 item for Remington to make.

Now, if you're one of the 30+ relatively small AR-15 assemblers, then a hammer forging machine is going to blow your budget. I have to imagine that Shaw and Wilson have or will soon buy hammer forging machines and we can start to see the price drop on forged barrels for AR-15s and other rifles that commonly get assembled or overhauled by individuals and gunsmiths.

 

[Maverick223]

The barrel maker has to recover the high cost of the investment.

Very true, but as Z mentioned that shouldn't take long for a decent size manufacturer, and when they do it really boosts production rates and cost of fabrication. Honestly I am surprised it costs $60-80.00.

 

[nhm16]

I have a sneaking suspicion that most of the hammer forged AR barrels come out of the FN plant in SC, which makes hammer forged .224 caliber barrels for SAW's. I'm pretty sure I read on ARFCOM (I know) or m4carbine.net that Noveske or another top-end AR manufacturer disclosed that's where their hammer forged barrel blanks came from. I'm pretty sure smaller companies like Daniel Defense or Bravo Company, say, didn't invest the millions in a hammer forging setup, when it would be much smarter to source the blanks from FN and have them finished.

As for the cost, I think it's just the novelty/latest and greatest factor that explains the cost differential.

 

[YaNi]

There is some misinformation in this thread.

Hammer forging is faster, but not cheaper. Hence the increased price. The benefits are negligable if the barrel is chrome lined. If I was going off to war, I couldn't care less if my barrel was hammer forged or mandrel cut.

 

[Z-Michigan]

YaNi, what's your source? The site I linked to is written by a mechanical engineering professor who has written a book on this process. More articles from him are found at:

http://technology.calumet.purdue.edu/met/higley/

Also-

couldn't care less if my barrel was hammer forged or mandrel cut.

Nearly all low to mid priced barrels that are not hammer forged are button rifled. In other words, gun drilled and then rifled with a carbide button. Cut rifling is very rare today and is found only on a handful of high end barrels, mostly custom aftermarket barrels for benchrest, service rifle or other long distance precision shooting. You will not find a cut rifled barrel on any military rifle made in the last 50 years unless it is a pricey aftermarket barrel installed for competition.

 

[Tirod]

The interior finish of a hammer forged barrel is a key item to accuracy and longevity. Button rifled barrels are the source problem that lapping cures. Button rifled barrels have a seriously rough finish that shaves gilding and lead off for hundreds of rounds - or at least would if they didn't coat over with scrap. Hammer forged barrels will not have that abrasiveness simply because the material is not microscopically torn into shape.

Machining metal isn't about a molecularly smooth finish, it's about applying a huge amount of localized pressure with a tool and ripping it apart.

Lapping, abrasive bullets, and borescopes have a market precisely because of button rifling. And button rifling doesn't seem to produce polygon bores - HK made those hammer forged twenty years ago because it was so easy. Most Euro battle rifles use hammer forged.

Not even the M4's use hammer forged, which reflects on the state of the art with American milspecs. Tooling and investments can dictate application and use.

 

[Maverick223]

There is some misinformation in this thread...Hammer forging is faster, but not cheaper.

Wrong! The equipment costs are significantly higher, but the cost of manufacturing are significantly lower.

 

[SSN Vet]

FWIW... Savage rifles have button rifled barrels and they aren't exactly known as being slouches in the accuracy department.

and ....

the cost of capital is always ammortized into the per piece price.... the ammortization period chosen is up to the manufacturer, but will often follow along the lines of the tax depreciation period.

and ....

Actual manufactureing cost is only one element in the sticker pirce of any product. What price the market will bear depends on many other factors such as brand image, supply, demand, competition, politics, etc...

Manufacturers that aren't keenly focused on making money aren't around for long.

 

[Zach S]

Wrong! The equipment costs are significantly higher, but the cost of manufacturing are significantly lower.

The cost of manufacturing is lower because the machine to do it costs more. Since that machine has to pay for itself, the cost is passed down to the consumer.

You've got to spend it to make it. I've worked in manufacturing for most of my adult life and have seen first hand how making parts faster and cheaper can cost more money for a while.

 

[Maverick223]

The cost of manufacturing is lower because the machine to do it costs more. Since that machine has to pay for itself, the cost is passed down to the consumer.

True, but that doesn't change the fact that manufacturing (not tooling) costs are reduced. I am sure that it takes a rather large manufacturing facility to make such an expenditure worthwhile, but when you churn out hundreds per day on one piece of equipment it can pay for itself in a relatively short period of time.

 

[MachIVshooter]

Drop it to ablsolute zero for 24 hours

...and exactly how do you go about doing that?

Kinda what I was thinking. Last I knew, absolute zero has yet to be obtained.

As far as the faster method, I don't see how hammer forging is it. It takes less than two minutes to push/pull a button down the bore and viola! Rifling.

Definitely truth in recovering the equipment cost. Hammer forging machines are on the order of a half million dollars. Button machines are pretty inexpensive and the buttons themselves are very low cost.

Me? I'll take a cut rifled tube over either

 

[ny32182]

So I think the bottom line here is that a chrome lined "hammer forged" AR barrel should not command a premium price to an end user based on performance over a... milspec type standard chrome lined barrel?

 

[Z-Michigan]

As far as the faster method, I don't see how hammer forging is it.

The hammer forged barrel is completely done on the inside once it's out of the machine. The button rifled barrel needs interior finish work. And I think the hammer forging machines spit out a barrel in under a minute.

So I think the bottom line here is that a chrome lined "hammer forged" AR barrel should not command a premium price to an end user based on performance over a... milspec type standard chrome lined barrel?

Their performance is probably marginally better, but if you're stuck with semi-auto-only and do something other than continuous mag dumps, you're probably not going to get enough (if any) discernible benefit to justify a cost premium.

OTOH if you are trying to build yourself the nicest possible AR that doesn't require NFA paperwork, and don't care about cost, the hammer-forged barrel is probably a little better.

 

[Maverick223]

Me? I'll take a cut rifled tube over either

Me, I am right there with you on that one.