M1 Garand Op Rod fail

Why are (hammer) forged rifling barrels not popular with people wanting and getting best accuracy with button or cut rifling if they're one of the best?
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The large companies tend to use the hammer forging, intermediate size companies tend to use the buttoning, and craft companies tend to use the cut rifling. All three can make an equally accurate barrel.”

http://bulletin.accurateshooter.com/2011/06/lothar-walthers-woodall-explains-barrel-making-methods/

Since the people who are paying craft companies to build custom rifles for world class competition it is natural that they would use more cut rifled barrels than any other method. It does not mean that cut rifled barrels are inherently more accurate since correlation is not causation.

What does correlate is that top shooters don't use factory rifles, they use custom rifles built for them. And custom rifle builders don't have access to a large pool of high quality hammer forged barrels, so their choice is between button or cut rifled barrels. Aftermarket barrel makers who use the button rifling method haven't been targeting the precision crowd, so it makes sense that you won't find them being used by the precision crowd. The same way GM doesn't market Camaros to the Amish...

What is the gauging - inspection process for cut rifled barrels?
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Depends on the manufacturer. But generally the inspection process involves slugging the bore to ensure tolerances are within spec and using a borescope to visually inspec the barrel. Which is generally the same inspection process as a hand lapped button rifled barrel.

Jimro
 
Based on what I understand, there is a difference between broaching and button rifling. A broach cuts steel; it is usually tapered or stepped so that a single pass makes larger and larger cuts. A button, though, is forced through the barrel under high pressure and "irons" the metal, compressing the grooves and smoothing the lands. No metal is actually cut away or removed.

Hammer forging involves use of a mandrel, into which the rifling is machined in reverse. It is put into the drilled barrel, then the barrel is hammered into and around it, forcing the barrel metal to take the (reverse) shape of the mandrel.

I am not sure any method can guarantee accuracy; I suspect the care with which the barrel is initially drilled and prepared may be more important than the method by which it is rifled. And that may come down to taking time and raising the cost.

Jim
 
Jim, you got it right in one.

The two most critical steps are gun drilling, and then bore reaming. If the bore and barrel are kept cool, variance of the ID shouldn't happen. Stainless can be a beast in itself, and some stainless will work harden easily, even during this.

The problem that I know about from button rifling, is that after the barrel is rifled, it has to be stress relieved before the OD is turned. If you don't do it correctly, the bore can open up. That is why I say its all up to the process, and if they did it correctly. Button rifling is a type of planishing process, in that it does squeeze the metal out of the way for the grooves. I have seen button rifled guns that were very accurate though, just as I have with cut or forged. The bore is should be smooth inside, similar to forged.

The one I didn't mention is electro-chemical. I'm not sure of how well this process works, especially for how smooth the grooves can be formed. I know Winchester patented either the process, or one method of it, and used it, but I'm not sure what they used it on.

On the checking of bores, air gauging, which most use, can check down to 0.0005", or some with a resolution of ten millionths of an inch. You can check both the bore and rifling this way, its just according to which plug gauge you use in the barrel.
 
It might be noted that with either button rifling or hammer forging, there is no real need to turn down the outside. A few makers have left the bulges or hammer marks alone; the reception was "mixed" to say the least, though there were reports of superb accuracy. I think that now all the makers turn (or grind) the barrels down for aesthetic reasons.

Jim
 
James,

On Hammer forging, I am not sure if polishing will affect them, as with no more than what is removed, I can't see it doing much if any at all, especially if it has been stress relieved. From what I've read, Remington, FN (Browning), and Ruger are using hammer forging now, along with several prominent European rifle manufacturers. They all, (or should), do stress relieving for the next process after the forging, as a barrel could split, warp, etc., later on. My guess is, they might have tried to get by the polishing process, hoping consumers would accept it, to save money.

The only thing that I can think of, when they mention a barrel opening up, is that maybe they tried to turn a barrel that either was not stress relieved, or the relieving wasn't done properly (held at the correct heat or coldness, for the right amount of time). All it takes, then, is for someone to report this, and automatically we'll have people saying the process is no good.


Below is a link to an article solely on hammer forging.


http://firearmshistory.blogspot.com/2010/05/rifling-manufacturing-hammer-forged.html

Note: This page says the forges are over $1 mil, and others say they are around $1/2 mil.
 
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Below is a link for a video about hammer forging at Steyr. They forge pre-turned or profiled barrels, instead of doing it later, and that is why they have the forge pattern, since they don't remove it after heat treating and before bluing. That would sure save some pocket change, but you have that patterned OD on the barrel.

https://www.youtube.com/watch?v=aCMzyNHkjpk

Below is a link for how Merkel does it (German):

https://www.youtube.com/watch?v=V7PBRWb6WFk
 
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I got a response from the CMP. They are sending me a return tag for the broken op rod. They will send me a replacement op rod at no charge.

I'm happy. Now to go back and read an in-depth discussion on match grade barrels... :)
 
I'm not aware of anyone shooting the the most accurate loads in competition using hammer forged barrels. Nor am I aware of any maker of them lapping them to uniform bore and/or groove dimensions to .0001" or better tolerance.
 
I'm not a barrel maker or an authority on it.I've just done some reading..and had a career in the machine trades.

At least Hart,Shilen,and Lilja are button rifled.

Badger was cut rifled,Obermeyer is,Kreiger...maybe Bartlein? not sure.

They have all made some famous barrels.

Per what is written by barrel makers discussing this topic,as has been mentioned,a button forms the rifling...as a thread forming tap forms threads,in a chipless process.
The barrelmakers say button rifling must be done before contouring,as there is a certain amount of "ostrich swallowing an orange" effect.Variance in wall thickness will result in variance of the rifling.

The size and surface finish of the bore before the button passes is critical.If you have done press fits on dowel pins,you know .0005 more interference makes a big difference in force required,plus if there is nowhere for the steel to go,if the bore is undersize,galling is more likely.I have seen the smeared cheese look of galling on the lands of a modest price barrel.

Some modest priced barrels do not have all te reamer marks lapped out before rifling.The bore has tool marks as if it had been cut with a boring bar.If the bore is a bit loose,the button does not smear the tops off the tool marks.Have you ever seen lands that look like a file?I have.

OK,all this is about cheap barrels.A precision,lapped hole makes it work better.
The "30 second vs 90 second" claim may apply to production barrels,but I suspect at Hart and Lija,a bit more goes into it.

So,yes,now there is stress in the barrel.Stress relief involves heating pretty hot,approaching critical temp,then cooling.Remember the bore,the rifling,is finished except for lapping.
Now its time to profile from the rough blank.Maybe stress relieve again.
After all this,its time to finish lap.

On a cut rifled barrel,the outside can be profile turned,and the bore drilled and finish reamed before stress relief.The rifling cutter puts no stress in the barrel.
IIRC,Kreiger double stress relieves and cryos before rifling.

Cryo and the heat of stress relief can effect the steel surface,so,post stressrelief,the bore is lapped,then rifled,then finish lapped.Nothing else happens to the bore.IMO,the cut rifled barrel creates a "fresher,sharper" bore.

I don't think hammer forging can produce quite the precision and definition ...the sharp,clean corners of the other processes.And,the barrel is inherently stressed by the process.You have to decide between work hardening and stress relief.Stress relief will ,I think,negate work hardening

I think hammer forging excels for producing military and general hunting barrels.The chamber can be formed at the same time,a nice throat,it can all be chromed or nitrided.I think a Daniel Defense bbl is crackerjack for a three gun or battle rifle.

They are all good for intended purpose.

I want a Kreiger for an AR I have...and,could be I'll only be semi-satisfied with less.BUT,aWhite Oak is significantly less money...

The bug hole tack driver is a joy,but,in reality,I'm not all that good of a shot!!

If I get an honest 5 shot .750 MOA rifle most of the time with some 1.00 MOA bench groups...That won't cut it in Barts Competition world where the standards are higher..but it will outshoot ME!
I'd probably trust a White Oak to do that.

I'd be disappointed with a Kreiger,maybe,if I couldn't get some pretty small groups.5 MOA? Maybe.But,from target center to bullet center,the difference between a 1 MOA rifle and a .5 MOA rifle is .250 at 100 yds.Its the radius .

Typical sandbag bench shooting,I doubt I hold that close.

FWIW,my fake 1903A4 and my Garand both have Criterion barrels on them.
They both shoot real well.It does not prove anything,but last time I put it on paper,checking sights before antelope season,I put a 12 in bull on a target at 350 yds.With my 2 1/2 x Lyman Alaskan,I used a6 oclock hold with the post reticle.Slung up,prone,left hand resting on my rucksack,3 shots went into just under 3 in,center of the bull.
As I said,proves nothing.But,no glass bedding,military stock and trigger,combined with my mediocre shooting,I won't complain.
 
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Just because you haven't heard of something doesn't mean it doesn't exist.

Here are two examples...

In 1999 fall British long range bench rest championship was won with a Tikka Continental, cal. 6,5x55. The range was 1000 yards, 10 shots, diameter of all impacts: 4,4".

http://www.tikka.fi/faq.php

Walter Wilkinson, 56, of Edgewood, NM, bested a field of 31 competitors—most using highly customized rifles—to take the Hunter Class Score World Championship title at the Fifty Caliber Shooters’ Association World Championships at the NRA Whittington Center near Raton, NM, held July 1st and 2nd. This marks the second year in a row that a competitor with an off-the-shelf Steyr HS.50 has won the Hunter Class

http://www.steyrarms.com/nc/news/it...ease-steyr-hs50-wins-world-championshipagain/

The Steyr SSG 69 has also won a number of European competitions, and the FN SPR has done very well on the tactical matches (including beating out the competition for the FBI sniper rifle contract).

The point being that you don't find custom rifles with hammer forged barrels, simply because small makers aren't set up to make hammer forged barrels and custom barrel makers aren't either. So custom rifles use cut or button rifled barrels, and factory rifles are much more likely to use a hammer forged barrel.

Heck, George Gardner has put together a number of rifles with Lothar Walther barrels that have won competitions, and those are button rifled (if made in America, those barrels made in Europe are hammer forged).

Top competitors want a premium barrel. All the premium barrel makers in America offer cut rifled barrels (and some also offer button rifled barrels). The lack of hammer forged barrels on custom rifles is simply a matter of no demand means no supply. If you had to pull a factory rifle off the shelf, it will likely have a hammer forged or button rifled barrel. A Savage, Tikka, or FN SPR will all shoot tighter than you can from a rest, and will shoot every bit as good as a Remington M24 with that Obermeyer 5R cut rifled barrel.

Jimro
 
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