Determining the direction of rifling in a barrel

I have a .45 cal barrel blank that I plan to use with a Greener Martini action to make a .45-70 rifle.The barrel has been cut off at both ends, and is unmarked.
I would like to know if there is a way I can determine which end should be the breech, and which the muzzle. I've read that barrels are rifled by pulling a cutter through them, and therefore the rifling will be smoother in one direction than the other. My problem is, since the barrel isn't marked, how do I tell the proper direction?
Rick W

Run a snug patch through it, on a swivel handled rod, that will tell you the direction of the rifling. And if your rod is indexed (you should have at least ONE indexed rod) you can tell its ratio as well.

As to directionality - if you lap the barrel (which for a quality barrel is important) it will smooth the irregularities of when the grooves and lands were cut.

Push a lead slug through it. If one end is looser than the other, put that at the breech.

And don't be surprised if you taper it, and it's a button rifled barrel, that it reverses itself.

"And don't be surprised if you taper it, and it's a button rifled barrel, that it reverses itself."
wesg:
I do intend to taper the barrel.Are you saying that due to the stresses/heat of tapering the barrel , that the interior roughness of the rifling will reverse direction?
If so, that would mean that I would only have a 50/50 chance of getting it right, even if I knew the direction of the rifling. Please clarify!
Rick W

The bore could open up in diameter as you turn it down. Generally considered an accuracy killer to have the bore looser at the muzzle than the breech.

Any barrel can do this. Button rifled barrels more likely than cut rifled, as there's a lot of compressive stress left in there after swaging the rifling in. Stress relieving is supposed to get rid of it, but I have one in my safe right now that it didn't work on. It was a gamble, I flipped the coin, and lost. Two others from the same maker weren't a problem. FWIW, the one that opened up still shoots fine, but it's a high pressure cartridge shooting jacketed bullets. Cast bullets could be another story.

I've also done some major turning down of cut rifled barrels for AR-15's. Can't detect any change in the bore size on them. Not to say the next one won't be a problem.

Thanks for the responses.
I tried a patch, and it definitely feels smoother in one direction than the other. I'll make the bullets go that way.
Thanks for the info about button-rifled barrels. I don't know if this barrel is button-rifled or not, so I'll take my chances and hope it doesn't change things when I taper it.
Rick W

wesg said:

Push a lead slug through it. If one end is looser than the other, put that at the breech.

And don't be surprised if you taper it, and it's a button rifled barrel, that it reverses itself.

Click to expand...

I'm sorry... I normally try to stay out of this type of thread because I always manage to kick someone's sacred cow... But I have to kick this cow none the less..

"don't be surprised if you taper it, and it's a button rifled barrel, that it reverses itself"

WTF!!! This myth has got to be one of the most absurd things in in the industry and completely ignores HOW barrels are made.

Barrel blanks of pre-hardened steel are drilled, rifled THEN contoured. IF the contouring were to open up the bore at the muzzle end, then button rifling (others believe cut rifling is the culprit) would be a complete and utter waste of time and money.

As you correctly stated in your follow up post: "Generally considered an accuracy killer to have the bore looser at the muzzle than the breech". However, what you don't state is that an even bigger "accuracy killer" is pushing a bullet the wrong way down the barrel.

So I'm making high end button rifled match barrels and I won't know if I can sell my product until I do all the work and air gauge it? If this were a real issue how would I stay in business?

Barrels do NOT "open up" when contoured. The machining stresses do not mystically effect the steel when we re-contour a barrel but not the manufacturer. Fluted barrels do NOT impart more stresses and ruin the accuracy. And cryo-stress relieving barrels has never been proven to do a thing (the reason there are so few companies left doing this). It's snake oil!

The best way to determine the direction of the bore is to look inside with a bore scope. Cut rifling is obvious. When viewed from the breach it will look smoother. When viewed from the muzzle you can see the edges (like a saw blade in miniature). Button rifled barrels are GENERALLY more smooth but look like ripples in the sand at a beach. The bullet should travel across the more gently sloping backs of the ripples not into the faces of them. If you don't have a bore scope find someone who does and ask them nicely if you can look down the bore of your barrel from both directions with it. I don't know anyone with a bore scope who would turn down anyone who asked nicely.

Running a patch down the barrel will usually offer LESS resistance in the SECOND direction than the first because the patch(es) become compressed on the first pass and offer less resistance on the second. Re-wraping the patch(es) or replacing them for the second pass will tell you nothing of value either since it is impossible to wrap them exactly the same each time. GENERALLY, IF there is a measurable difference in the bore from end to end you are only talking about a couple ten-thousandths (0.0001"). IF you really need to know which end is tighter the ONLY reliable way to know is to gauge it with a plug gauge. AND GENERALLY the tight end IS the muzzle... Not always, only MOST of the time.

You real need to know which direction the tooling marks run. Don't worry about which tighter. And when you re-contour the barrel, reference the bore NOT the OD. Worry about leaving enough meat on the muzzle to prevent failure, NOT opening up the bore on the muzzle end. It will NOT be an issue!

You must have never turned one down ;-)

4 tenths bigger at the muzzle than at the breech. Stumbled across my 'slugging' notes looking for something else. Lapped (as all 'high end button rifled match barrels' are) match barrel from a prominent maker. The other 2, from the same maker, weren't a problem. So I can only assume this one wasn't properly stress relieved.

And just to piss you off a little more, it's been documented that turning down hammer forged barrels makes them close up ;-)

And one more little myth busted for you: You CAN constrict the bore with a clamp on front sight. And it takes smaller screws and less torque than you think.

wesg said:

You must have never turned one down ;-)

4 tenths bigger at the muzzle than at the breech. Stumbled across my 'slugging' notes looking for something else. Lapped (as all 'high end button rifled match barrels' are) match barrel from a prominent maker. The other 2, from the same maker, weren't a problem. So I can only assume this one wasn't properly stress relieved.

And just to piss you off a little more, it's been documented that turning down hammer forged barrels makes them close up ;-)

And one more little myth busted for you: You CAN constrict the bore with a clamp on front sight. And it takes smaller screws and less torque than you think.

Click to expand...

Funny... First you make accusations, "You must have never turned one down ;-)". Then to make your point look better you change your story, calming that lapping is the cause. Then of course there are the "slugging notes" HORSE MANURE!!!

4140 pre-hardened has a yield strength of about 90,000PSI. That is the amount of force it takes to permanently alter the dimensions of the steel. Lapped, un-lapped, button rifled, cut rifled... It does not matter. You are NOT imparting or relieving 90,000PSI of stress from the barrel by turning it down.

"So I can only assume this one wasn't properly stress relieved" LMAO!!! NO ONE, not one single manufacturer of barrels stress relieves barrels!!! Again, 4140 is stress relieved at temperatures of 1600° - 1700° (870 - 925 C). That would take the temper out of the steel since the tempering range is 1525° - 1625°. SO I guess NONE of the barrels from "prominent maker(s)" are "properly stress relieved"

See:

Welcome to Shilen Rifles, Inc.
Hart Rifle Barrels
Douglas Barrels, Inc
Lilja Precision Rifle Barrels

NOT one word about stress relieving... EXCEPT Shilen Rifles FAQ

Lilja Precision Rifle Barrels - Articles: The Making of a Rifle Barrel

"A disadvantage to this method of rifling (characteristic of other cold forming operations too) is the fact that stresses are introduced into the steel. If they are not removed through heat treating, other problems may result such as potential lengthwise splitting of the barrel. Also, inside diameters may open up during the contouring stage, or warping of the barrel may occur. Fortunately these stresses can be removed through a simple heat treating operation.

Some makers will next contour the outside of the barrel, and if the barrel is to be lapped it is done after contouring."


I stand corrected. You were right. Not one word.

A bunch of words, actually. We can pick nits over whether this re-tempering is 'stress relieving' per steel industry guidelines. I personally don't believe it is, so on purely technical grounds I guess I have to agree with you.

I have a 375 caliber unturned Douglas Stainless Steel blank here that is a curiously blue color all over. From 'stress relieving' would be my guess.

As for slugging notes being horse manure, I actually do have a couple sheets of paper with a shitaton of numbers written on them, measured to tenths, 'passed thru', 'breech end', 'muzzle end', plus subjective notes about feel. I do recall with this 6.5, that started as a HV profile and was turned down to a medium Palma, that the slug would nearly fall out the muzzle after being pushed halfway through from the breech.

And where did I claim lapping was the cause?

I don't know of a button barrel manufacturer that does not stress relieve their barrels after buttoning. Generally it's done at 1050-1100F. This temperature maintains a hardness of Rc28-29. Soak time is longer at these temperatures, than at 1500F but that would draw the hardness and strength down to unsafe levels. Even after stress relief, I have never seen a buttoned barrel that did not change dimension when externally machined. It's not a matter of removing or adding stress. It's a matter of exposing stress that's already there by removing constraining material. That being said this movement can be compensated for, and many fine barrels are made with the buttoning process.

Thanks James Lederer, They do stress relieve in an oven. The better shops have vacuum ovens. Normally they lap after contour to final dimension. I have used my Deltronic pins to check the bore on some unlapped barrels. They ranged from .0001"-.0002" larger after contour.

butchlambert said:

Thanks James Lederer, They do stress relieve in an oven. The better shops have vacuum ovens. Normally they lap after contour to final dimension. I have used my Deltronic pins to check the bore on some unlapped barrels. They ranged from .0001"-.0002" larger after contour.

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Well pretty much everyone stress relives after rifling these days. Even some of the cut rifling guys. Well not Ron Smith in Whimbourn, hes sort of old school. The only one that I haven't asked about it was Hart. So before I opened my mouth and made an ass of myself, I emailed them and asked.



And as you can see from their responce, they do. Just like all the other kids on the block. As for expanding a bit after turning? Who gives a rats ass about .0002 inch. There is not "word one" that you can do about it anyway and they still seem to shoot well so who cares. Its just another peice of usless but extreemly fascinating trivia.

butchlambert said:

They ranged from .0001"-.0002" larger after contour.

Click to expand...

At what temperature?

I stand corrected on the issues of heat treating. HOWEVER, IF you read my original post you will find that that is NOT my point any way.

MIBill said:

I stand corrected on the issues of heat treating. HOWEVER, IF you read my original post you will find that that is NOT my point any way.

Click to expand...

It was kinda long winded. What exactly was the point you were trying to make ?

speerchucker30x3 said:

It was kinda long winded. What exactly was the point you were trying to make ?

Click to expand...

Oh, OK I read it again. The barrel expanding because of stress thingy. Most of the barrel makers seem to stand behind that fact. I suppose they should know those sorts of things, they do it for a living. I have spoken to a couple barrel makers about this over the years and from what I recall the consensus was that stress reliving didn't completely eliminate this phenomenon, although it did improve things dramatically. Also, most of the barrel makers seem to leave lapping until the very end, after the barrel has been turned to final diameter. I suspect that doing this last may even out the ID of the bore slightly in the event that small diameter areas have expanded a bit, as well as removing burrs and tool marks.

I personally don't care about such things like barrel expansion from turning because its something that's beyond my control and if a guy wants a .550 muzzle on his barrel I'm going to see that he gets it. Light barreled hunting rifles are not bench guns anyway, so again, I don't care and because of that I have never bothered poking standards down the barrels I have turned down and I don't know why other gunsmiths worry about it either. Most all of the barrels I have turned down over the years have shot pretty much the same as they did before I turned them and most of them were button rifled. I have even had a hand full that warped badly when turned and after straightening they shot well enough that the customer was happy with them. But I always stress that messing with barrels is a dangerous occupation and if it warps or does not shoot after its not on my plate. Maybe I have just been lucky.

If you want hard numbers on how much they expand on un-stress relived verses stress relived and turned barrels I suggest you contact Dan Lilja. He's a real gadget and numbers nut and if anyone had hard data on the subject it would be him.


Geoff Kolbe of Border Barrels has the following to say on the subject:

http://www.border-barrels.com/articles/bmart.htm

When contouring a barrel, a lot of metal is removed and if there is any stress in the metal then this is relieved by the removal of material. This may result in a barrel that started out as straight ending up as bent. This is not usually a problem when cut rifling a barrel as this does not induce any stress, but button rifling induces a fair amount of radial stress which is relieved by turning the barrel down. What happens then is that as you remove metal from the outside so the dimensions on the inside grow larger. If you turn a sporter barrel with a skinny muzzle from a buttoned blank then you find the barrel is bell mouthed and the bore diameter is a thou' or more bigger at the muzzle than the chamber - definitely, not good! Buttoned barrel blanks have to be stress relieved before profiling to prevent this expansion at the muzzle.

Geoff Kolbe Border Barrels

ADD NOTE: I think the barrel makers intentionally withhold a lot of information like this because a lot of people have no grasp of mechanics and physics and it just confuses people to much. Even in my corner of the industry I try not to over complicate things to much and try to answer their questions very pointedly. Experience has taught me that to much information in the wrong brain can be detrimental to my mental health and can lead to an uncontrollable urge for me to slap people. Its not healthy.

speerchucker30x3 said:

Oh, OK I read it again. The barrel expanding because of stress thingy.

Click to expand...

Sorry, I guess I'll have to take a hit or not being clear enough also.

The point was/is that it is far more important to shoot the barrel WITH the tooling marks, if they can be determined, than to worry about which end of the bore is bigger. AND that the only sure way to determine which way the tooling marks run, if it can bee seen, is to look at the bore with a bore scope.

{END INITIAL POINT}

IF the bore were to "open up" .0001" -.0002" there are damn few people that could measure it accurately in the first place... Secondly there is nothing you could do about it if it did happen... And third it is unlikely to be an issue that you could attribute to ANY ONE specific thing.

Accuracy is a damn elusive creature and one that takes a GREAT deal of skill to pursue. Experience has taught me that MOST shooters would have a hard time holding MOA with a rifle capable of holding quarter MOA. A HALF MOA group (@ 100 Yrds) fired from a .308 cal rifle would JUST barely be covered by a nickle (not quite by a penny). I can count on my fingers the number of groups that size, or smaller, I have seen others shoot outside of SERIOUS competition, and I have been a RO for nearly 30 years. Seriousy, it is not at all common.

Well, I have owned a couple bore scopes and personally I have found that they don't really tell you a lot. I have never noticed that I was able to tell which way a cutter was drawn when using one. That much is certain.

I stayed out of this debate originally because I have tried to determine which way a button or cutter was pulled on occasion and I truthful never found a way to do it and be even 55 to 45% sure of direction even when the actual cutting direction was known. I have squinted, peeked and poked. I have looked with bore scopes, magnified areas with special camera lenses to the point where a pea sized area of the barrel filled the whole area of a 20 inch computer screen. I have pushed patch's, laps and even pulled over sized brushes through with the bristles backwards and NADA ! If there is a "for certain" way to do it, I've never found it or been told.

With a properly lapped barrel I would agree... However, I doubt that is what OP has. Factory and lower end barrels I have never had any big problem determining which way the cutter was drawn, but then I may just have a gift for seeing things like that.

Patches, laps, brushes... They just don't tell you a thing. If they do it is probably time to re-barrel!