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gunsarefun
10-14-2011, 8:24 AM
What is the difference between a barrel that is hammer forged vs. not? Benefits? Especially with keeping only semi auto fire in mind....

Dhena81
10-14-2011, 10:25 AM
One barrels steel is forged with a hammer and the other is not :D

captbilly
10-14-2011, 10:45 AM
Hammer forging generally is in reference to how the rifling was created rather than how the barrel steel was formed. I have not heard of any method of forming barrels that results in significantly longer barrel life. The military has poured money into extending the life of artillery and tank guns because some of those guns have lifespans of only 100 or so rounds. But the methods used on those guns involve a separate barrel liner made of exotic materials (refractory metals and even ceramics have been tried with more or less success). In the case of hanner forging the barrel is pounded over a mandrel with the rifling in it to create the rifling. The issie with every type of rifling is that the proceedure used to create the rifling also tend to build stresses into the barrel. When the barrel is heated or cooled those stressed areas expand or contract more than the surrounding area causing the barrel to bend slightly, resulting in a moving impact point for the bullet. The least residual stress is caused by cut rifling (done one groove at a time). This is how the custome barrel makers like Krieger make thier rifling, but the method is time consuming and therefor expensive. Most factory barrels are rifled using a single broach pulled through the barrel, and you can get some pretty good barrels this way, but cut rifling is what pretty much all the top target shooters use.

I do not know what the advantage of hammer forging is supposed to be, but it would seem to me to be prone to inducing stress in the steel, like every forging process.

CK_32
10-14-2011, 10:49 AM
Hammer forged should last like 3 to 5 times longer than one that's just chrome lined from what I've been told.

I don't know metals but I figured for $50 more I'd try it. So I went with a BFH bcm middy and because it was the only one left for sale. I doubt I'm ever going to shoot out my barrel but like I said for an extra $50 who is it going to hurt. And I like the little bfh stamp on the register looks cool :D

chicoredneck
10-14-2011, 10:54 AM
Like captbilly said, hammer forged is a description of the manufacturing process of the barrel. If my understanding is correct, hammer forging does not offer any benefits over other manufacturing process except that it is a cheap way to mass produce barrels.

kendog4570
10-14-2011, 11:02 AM
Its another way to rifle the barrel. (cut, broached, buttoned, hammer forged, did I forget any?)
The real benefit of hammer forging goes to the guy making them. The first barrel is really, really, really expensive, the rest are not.
Quality with any of the methods is all depending on the approach of the person doing the process. They all have produced some incredibly accurate barrels. They all can fail miserably if done poorly.

dieselpower
10-14-2011, 12:46 PM
http://www.border-barrels.com/articles/bmart.htm

This is written for the common guy to understand. Mr. Kolbe's shop is well regarded as one of the best custom shops in the UK.... He is the UK equivalent of our Mark LaRue. Small shop in relation to the industry big boys with high end quality as a trade mark. Not well know except for those insiders. Most non-AR guys have never heard of LaRue. In any case its a good read that explains a lot.

Richard Erichsen
10-14-2011, 9:21 PM
What is the difference between a barrel that is hammer forged vs. not? Benefits? Especially with keeping only semi auto fire in mind....

... About 25-50% markup.

Seriously though, it is supposed to increase barrel life, which can be an important consideration for weapons intended to be used primarily in full automatic. There are other methods of achieving improved barrel life that can be applied after the fact (nitriding comes to mind) even hard chrome, correctly applied, can aid in reducing bore, chamber and throat erosion. The actual benefits can vary significantly with the typical use and cartridge load characteristics.

None of this really matters to the average shooter who is probably firing less than a coupled thousand rounds in a year. A typical barrel can generally be expected to last 6000-7000 rounds while maintaining like-new accuracy for many of the small bore/high velocity calibers. That accuracy will tend to diminish as the round count increases (along with many other components of the rifle which will be near or have already exceeded their component "overhaul" schedule).

High pressure/high velocity (small bore in particular) calibers and hotter loads in general tend to eat barrels faster than slower, low pressure loadings, with larger non magnum calibers like common .30 cals having fairly long service life.

If a barrel has an effective useful life of 10-20K rounds, that's a whole heap of ammo that may be several times the cost of the rifle itself. Nothing lasts forever. By the time a barrel has fired tens of thousands of rounds a whole lot of other parts will have worn or broken.

R

Knife Edge
10-14-2011, 10:36 PM
Is that how the get the polygonal rifling?

Seeker
10-14-2011, 10:50 PM
A cold hammer forged barrel starts as a thick rod of steel and as the bore is made a mandrel is inserted into the bore. With the mandrel inside the bore tungsten carbide hammers continually hammer at the rod shaping it into a barrel while at the same time to bore and rifling are being formed around the mandrel.

This forging process does two things:

1.) It increases the density of the steel in the barrel, giving the barrel a longer service life. and...

2.)The bore and rifling are molded around the mandrel inside the barrel resulting in a more accurate and consistent barrel.

Normal barrels that have cut-rifled bores have microscopic burs in the metal inside the bore resulting in having to "break in" the barrel which usually is a continuous process of shooting a certain amount of rounds and cleaning the bore and repeating the process a couple of times.

A cold hammer forged barrel doesn't need to be "broken-in" and is ready to shoot right out of the box.

Inquirer
10-15-2011, 5:57 AM
A cold hammer forged barrel starts as a thick rod of steel and as the bore is made a mandrel is inserted into the bore. With the mandrel inside the bore tungsten carbide hammers continually hammer at the rod shaping it into a barrel while at the same time to bore and rifling are being formed around the mandrel.

This forging process does two things:

1.) It increases the density of the steel in the barrel, giving the barrel a longer service life. and...

2.)The bore and rifling are molded around the mandrel inside the barrel resulting in a more accurate and consistent barrel.

Normal barrels that have cut-rifled bores have microscopic burs in the metal inside the bore resulting in having to "break in" the barrel which usually is a continuous process of shooting a certain amount of rounds and cleaning the bore and repeating the process a couple of times.

A cold hammer forged barrel doesn't need to be "broken-in" and is ready to shoot right out of the box.

Great post; very concise and understandable answer.

--Inq

dieselpower
10-15-2011, 6:41 AM
A cold hammer forged barrel starts as a thick rod of steel and as the bore is made a mandrel is inserted into the bore. With the mandrel inside the bore tungsten carbide hammers continually hammer at the rod shaping it into a barrel while at the same time to bore and rifling are being formed around the mandrel.

This forging process does two things:

1.) It increases the density of the steel in the barrel, giving the barrel a longer service life. and...

2.)The bore and rifling are molded around the mandrel inside the barrel resulting in a more accurate and consistent barrel.

Normal barrels that have cut-rifled bores have microscopic burs in the metal inside the bore resulting in having to "break in" the barrel which usually is a continuous process of shooting a certain amount of rounds and cleaning the bore and repeating the process a couple of times.

A cold hammer forged barrel doesn't need to be "broken-in" and is ready to shoot right out of the box.

Great post; very concise and understandable answer.

--Inq

I disagree...

Hammer forging is cheap, efficient and produces an acceptable barrel for the buyer. Its an improvement in the barrel making process for the manufacturer...NOT the consumer. The consumer benefits from a cheaper process which produces an acceptable grade product.

A high accuracy barrel will be cut and cost a bit more. It will lose its accuracy after a few thousand rounds because its not made for longevity.

I will also point out a cheaply hammered barrel will not last long and be extremely inaccurate. So when I say HF is a cheap process I mean cheaper than the equivalent cut or button rifled barrel. It still takes a bit of skill and a proper technique to produce a hammer forged barrel. If tooling isn't maintained and crappy bar stock is used, the result is a poor barrel.


oh and chrome lining determines accuracy in a Chrome Lined barrel. I don't care if God/ Jesus and the Holy Spirit hammered the barrel... if Joe Blow chrome lined it afterward the barrel will be inaccurate. Chrome degrades with use. So the process used to make the barrel has no effect on accuracy degradation if the rifling is then chromed. The wear on the chrome determines the accuracy error over time.

A non-chrome lined cut barrel, made by an experienced barrel company will be the most accurate barrel for 3-6 thousand rounds over anything else.

jgraham15
10-15-2011, 7:07 AM
Here's a thread on cold hammer forged barrels

http://www.ar15.com/forums/t_3_118/549709_Cold_Hammer_Forged_Barrels__.html

chicoredneck
10-15-2011, 8:19 AM
I disagree...

Hammer forging is cheap, efficient and produces an acceptable barrel for the buyer. Its an improvement in the barrel making process for the manufacturer...NOT the consumer. The consumer benefits from a cheaper process which produces an acceptable grade product.

A high accuracy barrel will be cut and cost a bit more. It will lose its accuracy after a few thousand rounds because its not made for longevity.

I will also point out a cheaply hammered barrel will not last long and be extremely inaccurate. So when I say HF is a cheap process I mean cheaper than the equivalent cut or button rifled barrel. It still takes a bit of skill and a proper technique to produce a hammer forged barrel. If tooling isn't maintained and crappy bar stock is used, the result is a poor barrel.


oh and chrome lining determines accuracy in a Chrome Lined barrel. I don't care if God/ Jesus and the Holy Spirit hammered the barrel... if Joe Blow chrome lined it afterward the barrel will be inaccurate. Chrome degrades with use. So the process used to make the barrel has no effect on accuracy degradation if the rifling is then chromed. The wear on the chrome determines the accuracy error over time.

A non-chrome lined cut barrel, made by an experienced barrel company will be the most accurate barrel for 3-6 thousand rounds over anything else.

I agree with you and the other poster. Large manufactures use hammer forging becuase it is cheaper and faster to mass produse. Small barrel manufacturing companies usually can not afford the initial cost of hammer forging equipment (it is very expensive), or they want to produce match quality barrels.

Hammer forging can make the metal stronger. It is similar to the diffirence between billet and forged recievers. Forged recievers are actually stronger than billet because the metal is placed under extreme pressure, aligning the metal crystals and forming a stronger structure. A similar process happens during hammer forging.

The biggest problem with hammer forging is the madrels that are used to form the rifling. After time the mandrels wear out and factories do not change the mandrel immediately. You end up with a run of rifles with poor rifling or barrels that may not be true to the rifling (straight rifling). The initial barrels manufactured with a brand new mandrel can be of high quality and smooth. Bottom line, the barrel is only as good as the mandrel. Buying hammer forged barrels is kind of like gambling unless you can bring a bore scope with you to the shop. Most are fine, but there are plenty out there that are not. As a general rule, a hammer forged barrel will foul more than a high quality cut and laped barrel, assuming no other barrel treatment was applied such as chrome plating, but not always. Hammer forged barrels have a reputaion for being less accurate than cut or button rifled barrels. This is less true today as it was 10 years ago. Hammer forged barrels do seem to have more consistent accuracy than they used to. However, nobody is winning matches with hammer forged barrels, at least not the last I heard.

Uriah02
10-15-2011, 8:49 AM
http://www.border-barrels.com/articles/bmart.htm

This is written for the common guy to understand. Mr. Kolbe's shop is well regarded as one of the best custom shops in the UK.... He is the UK equivalent of our Mark LaRue. Small shop in relation to the industry big boys with high end quality as a trade mark. Not well know except for those insiders. Most non-AR guys have never heard of LaRue. In any case its a good read that explains a lot.

Good post!

chicoredneck
10-15-2011, 8:53 AM
This is a good explanation: http://bettincustomguns.com/Technical%20Information/Barrel%20rifling%20techniques.htm

dieselpower
10-15-2011, 8:23 PM
This is a good explanation: http://bettincustomguns.com/Technical%20Information/Barrel%20rifling%20techniques.htm

I don't know who "bettincustonguns.com" is, but they need to give credit to Mr Kolbe when they repost and plagiarize his work.

That "write up" is nothing more than Kolbe's work reworded in some places. :kest:

RRichie09
10-15-2011, 11:32 PM
So...

HF = longer life
Cut = better accuracy

TheHammerOfTruth
10-15-2011, 11:52 PM
So...

HF = longer life
Cut = better accuracy

Basically......yes

Sunday
10-16-2011, 12:01 PM
Will the differences be noted in real life use? That is what I wonder.

dieselpower
10-16-2011, 12:30 PM
So...

HF = longer life
Cut = better accuracy

Basically......yes

Will the differences be noted in real life use? That is what I wonder.

sorta yes and sorta no.

A barrels life is decided in many ways. The chrome lining really determines what we consider a lifespan. As would what the barrel was made from, not how it was formed determines that as well. A Stainless Steal will not resist heat as well as a Chrome Moly

HF barrels is just a process to make it. Nothing more. It gives no more or less than any other when you factor out accuracy. A cut rifling, non chrome lined has the potencial to be more accurate, but you can made a barrel harder thus more resistant to flex and heat and corrosion by hammer forge. To properly cut threads / rifling, the metal must be weaker than the tool used to cut that thread...so an extremly dense, hard barrel can't be cut well.

Its a balencing act really. Barrel steel vs rifling with use as a scale to judge it by.

So if by longer life you mean sitting on a shelf corroding, yes a HF will outlast a milled barrel. Cut, non-chrome lined rifling will wear out fast in use. Cut Chrome lined rifling will last longer, but the chrome lining determines the accuracy and the cut rifling needs to be oversized to accomdate that chrome lining.

The same is true for HF. Its the chrome lining you care about, not how the oversized rifling is made.

if you are blasting away with hot fast loads, that will wear the throat out and the rifling...which will wear out the barrel no matter how it was made. HF doesnt give you anything over cut when the lining is abused the same way.