Do hammer forged barrels primarily employ polygonal rifling? Aside from higher-end match type barrels are there any appreciable differences in accuracy to be gained from hammer forged vs. “standard” (broach, button cut) AR barrels or are there other factors that play into this such as consistency of chrome lining, chamber/bore dimensions, etc? I’m not looking to win any matches at this point, just curious.
Thanks.
I don’t know of any AR barrels that are hammer forged and have polygonal rifling.
Good article on hammer forged barrels explains the reason and benefits.
http://technology.calumet.purdue.edu/met/higley/Precision%20Shooting%20Magazine%20-%20November-%202005%20(Vol_%2053%20-%20No_%207).htm
I seem to remember reading a PDF on hammer forged barrels that stated one byproduct of manufacture for hammer forging was that at least one of the edges of the lands had to rounded off in order for the hammer forging mandrel to be removed from the bore without damaging it. I know that my AK’s barrel is cold hammer forged (all mil-spec AK barrels are, since cold hammer forging is the most cost effective way to mass produce a barrel) and it has both of the edges of the lands rounded off. I wouldn’t say it looks identical to my G21 service weapon’s barrel (which has true polygonal rifling), but it certainly is close. Lemme see if I can dig up the PDF…
Thank you. I thought that Noveske’s N4 LW barrels were HF and had polygonal rifling, but I don’t have that from a reliable source.
Novoske N-4 hammer forged barrels I think use conventional rifling with double thickness chrome lining. The SS barrels use the polygonal rifling.
i’ve yet to see a hammer forged barrel outshoot a cut or button rifled barrel in terms of accuracy. hammer forging is a way to make barrels quickly a cheaply and while it may be argued that there are accuracy benefits, until you start seeing them win competitions i would suggest that the jury is still out.
an unplated chf barrel will last longer than a standard button or cut rifle barrel but once you add plating there is nothing in it.
That’s what I thought, at least re: match-grade barrels, but don’t these often have a fair amount of additional finish work involved compared to so called “mass produced” barrels?
FYI, this older post is what caused me to ask the question (see Mr Davis’ response about 3/4 the way): https://www.m4carbine.net/showthread.php?t=455
i’ve yet to see a hammer forged barrel outshoot a cut or button rifled barrel in terms of accuracy
Aren’t Steyr SSG69 barrels hammer forged? 
Keith
Yeap so does every gun manufacture in Europe if not all of them at least 90% do.
IIRC all pistol barrels are hammerforged, and all military Euro barrels. HK was hammerforging in the '70’s.
The biggest technical advantage to hammerforging is that it doesn’t leave a rough machined surface on the barrel that leads up as much. This leads to an initial advantage in accuracy as the barrel shoots from round one much like a lapped barrel, without needing extra work or expense.
Polygonal rifling is also reputed to add a small advantage in speed as it is purported to seal better with less gas bypass. It can be easier to clean, as there is no corner that is difficult to get a patch into, or harbor corrosion.
One thing to consider is that a hammerforged barrel is inherently stronger than a billet drilled and button rifled. Grain structure is controlled by being pressed into the rifling, not being cut out. For the shooter, the barrel moves around less warming up.
The recreational shooter may not do enough to see any of the results, but the militaries who specify hammerforged report fewer barrels shot out, better retained accuracy, and less cost over the life of the weapon while fielded. As more hammerforging equipment comes on line, the increased volume and less cost will become a standard, as it already is for most major firearms makers in America already.
Wow, so all the Sako TRG-42s and TRG-22s out there aren’t accurate because of the cheap barrels they are using. Funny, because they shoot as well as my AI ( Cut rifle Border ),Pac Nor, Lilja, ( buttoned ) , Kreiger ( cut rifle ) rifles
If one is looking at a basic middy carbine without free floated hanguards, is the additional CHF cost worth it or would it even matter?
I just got my lower today, need to get an upper.
As well as the SSG04, SSG08, SBS ProHunters. If I’m not mistaken all Steyrs are. As mentioned aboce TRG’s are as well. I think both the SSG and TRG are Highly sought after for their excellent accuracy
CHF is implied to give advantages in longevity and accuracy but I believe the CHF barrel thing in AR’s is mostly hype. sure there may be theoretical differences but no one has been able to quantify those differences that I have seen. ymmv…
you might notice that CHF is not a spec on the original TDP and the amount of ink spilled here defending that is legendary. there have even been threads discussing “better than milspec” which have gotten a lot of play usually with the consensus that a 6920 (or its equivalent) is all you will ever need.
I want to add that it is your money and if it makes you feel good, you should do it, however…
however, money doesn’t grow on trees and I have to buy other things to complete my build.
It all depends on how you are going to use it as well. One of the supposed advantages is barrel length of life being longer with the CHF. The effective range of the 5.56 is only so far and the difference in .5 moa and 1.5 moa isn’t really that big of a difference in it’s effective range at man sized targets, however if trying to shoot 3" plates at 300-400 yards is your goal, then the most accurate barrel would be what you need to spend the money on
Not to throw coolant on a fire (coolant will burn quicker than motor oil, btw) the FN SPRs also have CHF barrels that also happen to chrome-lined! And they shoot, too.
So, apparently, there is more to the story than CHF vs Cut Rifled or Buttoned.
As an engineer I’d think the internal stresses on CHF would be by far greater than buttoned which would be greater than Cut Rifled.
I imagine that how well the interior is lapped, the quality of the tools (mandrel for CHF, button for button…) also play a large if definitely difficult to discern role.
There are many ways to accomplish a single task.
IMHO its pretty much of a toss up, and if one does have a small edge over the other in inherent accuracy, it is insignificant when using a RDS and shooting ball ammo. And as for barrel longevity, look at the BCM conventional rifled barrel in “Filthy 14”. I do think the CHF barrels might be a little better choice for a lot of full auto shooting .
Hard to argue with that.
I’ve done just informal comparisons between my BCM standard and my Rainier Arms with a DD CHF LW barrel, but the standard BCM shoots a bit more accurately. Both are plenty accurate, but the standard BCM shoots a bit better so far.
I actually remembered about “Filthy-Fourteen” today and the fact that it was a standard barrel.
My own rifle will probably never ever be run like that, so that fact assuages my concerns.
There is like a $70-$90 difference between the two, and there is a lot of stuff I need to get for my upcoming rifle.