Why are hammer-forged barrels for the AR-15 more expensive?


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migkillertwo
June 11, 2010, 09:57 PM
I imagine that they would be cheaper, I mean the process was invented in order to make barrels cheaper to build.

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-v-
June 11, 2010, 10:07 PM
I think its the manufacturer levying a "fee" for having to invest in the equipment to make them. While to make hammer forged barrels is quite cheap, to invest in the tooling to do it is quite expensive. Hence why most commercial barrels are button-rifled, because that machinery is relatively inexpensive to purchase for manufacturers.

migkillertwo
June 11, 2010, 10:14 PM
I'm guessing that's why most Com-Bloc AK barrels are hammer forged.

Tirod
June 11, 2010, 11:15 PM
Most Euro rifles are hammer forged and have been for 30 years. Most pistols are hammer forged - but that's a 6-7" piece of steel, and a bit less expensive machinery.

Many American sporting rifles are hammerforged, they just don't want to let you know - because the American public thinks button rifled is better for some reason. AR's are button rifled because the M4 and M16 contract requires it, no better reason than that. That leaves all the small barrel makers with button rifle equipment because the art and science of it is standardized and the equipment affordable. Laying out millions for a new hammerforging machine is way beyond them fiscally and unjustifiable for the small number of barrels made. The thing has to run 24/7 to start breaking even in the American economy.

The new Improved Carbine contract might shake that up. What will happen is that as the hammerforging machines start to recover their investment, the price on barrels will start be competitive and even punishing. The button rifled makers will die off pretty quick after that. Precision and custom makers will still be around, just not as many.

Advantages? Well, hammerforged barrels are more consistently concentric - some button rifled barrels can't use a suppressor because the bore is significantly off axis. The consistent wall thickness reduces point of aim shifting when warmed up, has less defects or anomalies, and can use polygonal or ratchet rifling. The bore is smoother, doesn't need break in shots, won't hold as much gilding brass or lead up, and should allow higher velocity for the same pressures because it's inherently less rough.

Button rifling has a dim future.

Offfhand
June 13, 2010, 07:32 PM
Hammer frorged is the cheapest way to make a rifle barrel, and the worst. But the term has been used like the "Hammer of Thor" to impress wally world Wannabees. So when you've bated a sucker, make him pay.

Tirod
June 13, 2010, 11:49 PM
Gotta ask why it's the worst. Button rifled barrels are inherently less concentric because they have to be drilled end to end. Only the best actually get them on axis, as said, some are so far off a silencer cannot be used on them - they'd get shot off. Barrels that don't have the hole down the middle will heat up on one side more than the other and bend as they warm up. MOA goes out the window.

Button rifling drags a carbide slug through the bore as it gets turned, ripping the material out in micro chunks and leaving a rough bore that has to be either lapped or cleaned a lot to prevent brass or lead buildup.

Precision cut rifling, one groove at a time, done by the best, is highly accurate, and expensive.

That leaves hammerforged, which literally compresses the metal onto a mandrel which already has the rifling on it - polished and without machine marks - controlled by CNC machinery and all the pressure it needs to not only create the shape needed internally and externally, but also removing the grain structure of the original stock and creating a new pattern that conforms to the shape.

Forging is an inherently stronger part with less dead weight and imperfections, which is why connecting rods, cranks for supercharged engines, and other high stress parts are usually forged. So are AR receivers and most stock aluminum wheels. Not cast, not machined billet - forged.

But some people don't seem to have a clue about machine processes, so they just throw insults and class warfare into the discussion when they can't argue the point with facts.

Done.

Z-Michigan
June 14, 2010, 12:17 AM
Hammer frorged is the cheapest way to make a rifle barrel, and the worst. But the term has been used like the "Hammer of Thor" to impress wally world Wannabees. So when you've bated a sucker, make him pay.

Yes, I'm sure that's why companies like FNH-USA and Steyr use hammer forged barrels on sub-MOA precision rifles. Just total crap, those world-class gunmakers don't know anything, and their military and LE purchasers are mindless idiots who wouldn't know the difference if they were being sold a Brown Bess instead.

Tirod's posts #4 and #6 are spot-on in terms of the processes and relative merits. For completeness I would add a fourth process, broach cutting, which was used in WWII and through the 1950's but is largely obsolete now, although still used by DS Arms for some barrels. It is a cutting process but using a broach instead of a single point cutter. Its quality level is probably in between button and single point cut barrels. As already noted the absolute best barrels are the single point cut rifled ones, however quality hammer forged barrels can be so good that it hardly matters.

As for cost of AR-15 barrels, I think it's simply a factor (largely as -v- said) of the equipment costs and perceived desirability of the barrels. I expect it will come down in the not too distant future. I wouldn't be surprised if the whole Cerberus family AR platforms (DPMS, Bushmaster, Remington) get hammer-forged barrels before long, since Remington has the equipment and has been putting such barrels on Model 700's since the 1960's IIRC.

FlyinBryan
June 14, 2010, 12:50 AM
Gotta ask why it's the worst. Button rifled barrels are inherently less concentric because they have to be drilled end to end. Only the best actually get them on axis, as said, some are so far off a silencer cannot be used on them - they'd get shot off. Barrels that don't have the hole down the middle will heat up on one side more than the other and bend as they warm up. MOA goes out the window.

Button rifling drags a carbide slug through the bore as it gets turned, ripping the material out in micro chunks and leaving a rough bore that has to be either lapped or cleaned a lot to prevent brass or lead buildup.

Precision cut rifling, one groove at a time, done by the best, is highly accurate, and expensive.

That leaves hammerforged, which literally compresses the metal onto a mandrel which already has the rifling on it - polished and without machine marks - controlled by CNC machinery and all the pressure it needs to not only create the shape needed internally and externally, but also removing the grain structure of the original stock and creating a new pattern that conforms to the shape.

Forging is an inherently stronger part with less dead weight and imperfections, which is why connecting rods, cranks for supercharged engines, and other high stress parts are usually forged. So are AR receivers and most stock aluminum wheels. Not cast, not machined billet - forged.

But some people don't seem to have a clue about machine processes, so they just throw insults and class warfare into the discussion when they can't argue the point with facts.

Done.

very informative, and makes perfect sense. i never knew they forged the material around basically what become your bore.

thx for posting, learned something new, but i do have a question.

how do they get the mandrel out of the new barrel? just press or drive it out? wouldnt this require such force that it would in effect leave (for my lack of better term) "pull out, or drive out" results as far as bore finish?

Button rifling drags a carbide slug through the bore as it gets turned, ripping the material out in micro chunks and leaving a rough bore that has to be either lapped or cleaned a lot to prevent brass or lead buildup.

ive always thought that button rifling does not cut, but "impresses" into the blank, the desired lands and grooves? just what ive been told, ive never seen a barrel rifled (ive only seen the little carbide slugs you mention)

LawofThirds
June 14, 2010, 01:36 AM
I do believe that the blank and the barrel would be formed together much like a nut and screw and you could, with a hydraulic press, simply "unscrew" the barrel off the blank.

Runningman
June 14, 2010, 01:47 AM
You won't see a hammer forged barrel on rifles used for benchrest competition. They are all either button rifled or cut rifling. I've yet to see a hammer forged barrel on a benchrest equipment list. Let alone hold a record.

Even Remington who has had hammer forging machines for decades does not use hammer forging on there 40X rifles. All the 40X rifles use button rifling.

You might want to read this article it was originally written in Precision Shooting magazine. http://firearmsid.com/Feature%20Articles/RifledBarrelManuf/BarrelManufacture.htm

JohnBT
June 14, 2010, 09:13 AM
Another interesting article on hammer forged barrels.

http://technology.calumet.purdue.edu/met/higley/Precision%20Shooting%20Magazine%20-%20November-%202005%20(Vol_%2053%20-%20No_%207).htm

Ruger bought barrels until 1990 and then bought its first hammer forge. Lots of history and pics.

"About the Authors

Vern Briggs is the Forging Process Engineer at Sturm, Ruger & Company, Newport, New Hampshire where he is responsible for barrel production.

James Higley is a Professor of Mechanical Engineering Technology at Purdue University Calumet, Hammond, Indiana where he teaches courses in design and manufacturing."

Tirod
June 14, 2010, 11:51 AM
Precision rifles are a completely different class. Military and hunting hold to 2MOA, it's all that is needed. 2MOA won't do in a precision shoot. The 6.5 Grendel holds the 600m record with an 1 1/2" group or less, IIRC. A military rifle would shoot a 12" group and still be as lethal as the caliber allows.

With that level of practical effectiveness in mind, getting a superior barrel cheaper from hammerforging would be required - any other decision using taxpayer dollars could result in Congress being bombarded with questions about who got paid off.

Note that Europe's gunmakers went hammerforged decades ago, but most were based on a government arms contract. The US requires a more competitive bid structure, capitalists want their share of the profit, and American labor could do the job. The cost/benefits ratios are changing - and eliminating the expensive and relatively hard to find skilled labor cuts down defects and returns. While the initial investment is higher, the long term results are superior barrels that meet spec over tens of thousands of units, just perfect for the accountants and bottom liners.

Hammerforging machines don't have bad weekends and family problems.

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