Hammer forged barrels
Does hammering forging barrels reduce their outside diameter. Also I would assume they are turned to size following the rifling process.
Thanks
Sage 1
Thanks
Sage 1
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Yes.
The blank is said to be about a foot long and larger diameter than the finished barrel.
Not all.
The Steyr Mannilichers and one model of Ruger had the hammer forge marks just polished smooth. Trademark or not wanting to release stresses? I don't know.0 -
Probably your best source of detailed info would be to do a google search, "hammer forging barrel process" .
As to if hammer forging vs cut rifling is more accurate maybe some members will weigh in. Probably when it is all said and done, accuracy depends more on how well the process is controlled rather than which process.0 -
Sage1,
Hammer forged barrels start with a short, fat billet which is fed onto a mandrel with the rifling present on it. This is fed into the hammer forge machine. The hammering is progressive and reduces the outside diameter while forcing the steel onto the mandrel, imparting the rifling shape.
Hammer forged barrels are not usually turned as this would release some of the stresses imparted by the process to the barrel and the barrel would warp or move in an unacceptable amount. Some company information is roll printed on the outside of the barrel as labeling and warnings.
A quote from my notes:
"Barrel hammering machines are built by Gesellschaft Fur Fertigungstechnik und Maschinenbau (GFM) in Steyr, Austria. They cost about a half a million dollars and can spit out a barrel every three minutes. These machines have reached a very high degree of development and are so sophisticated that they will not only hammer the rifling into the barrel, but it is also possible to chamber it and profile the outside of the barrel all in the one operation. Only large scale arms manufacturers and ordinance factories have pockets deep enough and barrel requirements insatiable enough that they can afford to buy and run such a machine."
This is a quote from the Armalon website, a barrel manufacturer in the UK:
"The hammer forging method of manufacture has been proved to produce superbly accurate barrels whose performance improves with use and which may peak in that respect well beyond 10,000 rounds, long after cut or button broached rifled barrels would be regarded as completely worn out. They may also be chrome lined for even greater durability. Unlike the other manufacturing methods, the hammer forging process aligns the molecular structure of the ordnance grade steel thereby gently and evenly work hardening the barrels. This makes them extremely stable in resisting dimensional changes to the bore, even where abrupt and significant transitions to the barrel's external profile may be involved. For example the highly popular and effective Armalon deep barrel fluting may be successfully applied to forged barrels."
Here is a good paper describing the process complete with illustrations for better clarity:
http://technology.calumet.purdue.edu/met/higley/NotesOnHammerForgedBarrels.pdf
Best.0 -
I have always been amazed by this process and will check the refferences. How can the mandrel be withdrawn when the forge process is complete? Looks like it would be forever stuck in the bore. 0 -
Mandrel removal?
Logic would dictate that the mandrel becomes more or less a machine screw. The difference being that instead of drilling and tapping a bore, the billet is formed around a screw.
Screw (mandrel) removal would then be a fairly simple matter. I know in many instances that heat could be applied to the surrounding material to ease mandrel removal by virtue of slight expansion. Whether this be the case for a super accurate and durable rifle barrel I cannot say.0 -
nord,
There is no need to apply heat to a hammer forged barrel since the barrels leaving the forging machine are extremely hot after all the pounding they take to make the barrel form.
The billet or finished barrel does not have full contact with the surface of the mandrel since there is a small amount of spring back to the barrel from the mandrel. The mandrel is pushed from the finished barrel.
Best.0 -
nord, not as easy as one might think. A 1/2 inch machine screw can only engage about 4 or 5 inches of theads. The small error in pitch will cause the screw to lock at this point. Hammer forge is a good trick.
I just read the referenced article. I see now that the mandrel is short. It does not fill the full barrel length. It looks to be only, guess what, 4 or 5 inches long. It is still a good trick.0 -
I was remiss if I implied a full length mandrel. The actual process is nothing new as long rifle makers of old forged barrels in a somewhat similar manner. On a long barrel they often worked from the middle to both ends of a new barrel.
Just to be clear... They were forging a flat strap of metal into a barrel. You'll be able to see the seam on such rifles. It's always located on the bottom barrel flat. The barrel was then straightened and rifled to complete the project. This is nicely illustrated in the FoxFire Collection.0 -
nord, no I was in error to assume a full length mandrel. Never-the-less, I am amazed the barrel comes out straight. 0 -
Great Article! 0
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