Are all hammer "cold-hammer" forged barrels polygonally rifled?

[NeedsMoreMillimeters]

I wasn't really sure which section to but this in, so feel free to move it if necessary.

So, I am a little confused as to what exactly happens with a "cold hammer-forged barrel" (I assume some actually use heat, but this seems to bee the standard nomenclature).

As I understand it, this method has its roots in WWII when the late war Germans were looking looking for ways to make MG barrel less expensively (specifically for MG42s). This also lead to polygonally rifling, since it was essentially the same process.

Now, currently a number of pistol manufacturers (Glock, HK, etc) market "hammer forged" barrels in their guns, and they all have polygonal rifling (like the image on the left). This seems to make sense for pistols.

But what about rifles (specifically ARs). A growing number of guns are coming with "cold hammer-forged barrels", but (which one exception) I have never seen anyone mention polygonally rifled AR barrels (would that even work with rifle rounds?). At the same time, considering the hammer forged process, I don't see how you could get anything else (it seems that actually cutting/drilling a barrel is the only way to get the sharp edges required for lands and grooves). So, perhaps an expert could educate me: Are the "cold hammer-forged" AR barrels truly polygonally rifled (like the image on the left), or it it just an new fabrication method, but with the traditional rifling.

Thanks.

 

[BBBBill]

Well, your image is reversed as posted. The polygonal is on the right, traditional on the left. I haven't paid enough attention to those to know much about them except for a few observations. First, polygonal rifling has been around for a very long time, as in the mid 1800s if I recall. Back in the 70s HK shipped some of the HK-91s with polygonal rifling. WW2 Japanese rifles had polygonal rifling. Whether all were hammer forged or done with a techniques similar to cut rifling is something I don't know. There are some currently produced barrels that are not polygonal in the same sense as the well known style - 5R, 7R, and Shilen's "Ratchet" rifling.

 

[Jonesy814]

Cold hammer forging a barrel does not lead to polygonal rifling. In hammer forging a barrel , the barrel is drilled them a mandrill with the reverse image of the desired rifling is inserted. This is inserted into the hammer forge which pounds the outside of the barrel and imprints the mandrill shape on the inside. If the mandrill is cut to produce conventional rifling than that's what you get. You can search YouTube to see videos of the process

 

[4v50 Gary]

No, you can have conventional rifling that is machine cold hammer forged too. I understand Rem's copy of the Russian 5R is that way.

 

[NeedsMoreMillimeters]

If the mandrill is cut to produce conventional rifling than that's what you get.

Ok, that makes a lot of sense. I have looked at a number of articles and videos, but none of them showed close ups of the mandrel, at least not enough to make out the pattern. I assumed that something with such sharp edges would be an issue for the hammering process (considering the metal flow), but it seems I was wrong.

 

[jaguarxk120]

My Mauser from about the late 70's has a hammer forged barrel and the lands and grooves are sharp and defined.
Also Ruger use's the hammer forging system on all of their guns.

 

[PRD1]

First, polygonal rifling has been around for a very long time, as in the mid 1800s if I recall. Back in the 70s HK shipped some of the HK-91s with polygonal rifling. WW2 Japanese rifles had polygonal rifling. Whether all were hammer forged or done with a techniques similar to cut rifling is something I don't know. There are some currently produced barrels that are not polygonal in the same sense as the well known style - 5R, 7R, and Shilen's "Ratchet" rifling.

The Japanese Arisaka barrels were rifled with Metford segmental rifling, in which the grooves are formed as 'segments' of smaller-than-bore diameter circles: they are not polygonal. The other rifling types you mention are all 'Ratchet' forms (that's what the 'R' indicates). Ratchet rifling is formed with grooves which are 'sloped' away from the raised driving edge, leaving no distinct opposite shoulder. Virtually any form of rifling may be hammer forged, using a mandrel of the appropriate shape.

PRD1 - mhb - MIke

 

[4v50 Gary]

Ruger has only four cold hammer forges that I saw when I went to their factory. They may have bought more by now. I know their 10/22 barrels are subcontracted out and even the Mini-14 barrels were sub-K out too.