Negative effects of threading the muzzle

[linebaugh]

Both buttoned and cut barrels open up to a degree when the muzzle is reduced for threading. How much this matters is questionable. I have used floating reamer pilots to prove this out before and after threading. Does it matter? I dont know, guns still shot fantastic. If you slug a bbl and cut on a constriction, rimfire does this a lot, it may negate one another. It may also be un-necessary. It seems like you would always want your bullet to exit under constriction but there are probably a few million guns to prove this theory unreliable.
One thing that bothers be is hanging big suppressors on small threads. This may not matter either but building on the robust side makes sense to me.
Another side note would be SBR configurations running high pressure. The shorter the bbl the more pressure the muzzle sees. Again does it matter in the big picture?
I go as big as practical when threading the muzzle and if the gun does not require it I sure dont thread.

 

[urbanrifleman]

This phenomenon is not exclusive to barrels, and can be seen when machining any round , tubular stock.

All barrels are machined. And it would seem that whatever "growth" there is, is a non factor in the practical sense.

I have certainly had customers that believed that cutting the muzzle of a barrel made it shoot worse. "Believed" is the operative word here.

 

[BoydAllen]

This is my understanding of how premium buttoned barrels are produced. They are taken through the rifling stage in cylindrical form. The buttoning process induces what is called banding stress in the steel. Before contouring, barrels are stress relieved to get rid of that stress so that when they are contoured that their bore dimension will not expand in proportion to the amount of metal removed. After contouring there may be a very slight reverse taper in the bore, that is taken out in the final finish lapping. As I understand it, because different lots of steel have different responses to a given size button, makers of those kinds of barrels may leave themselves more metal to remove during finish lapping as compared with cut rifled barrels.

In the case of cut rifled barrels, steel is delivered from the mill ready to drill ream and rifle. Before rifling, after reaming they are lapped or honed to produce the bore (top of lands) diameter and finish, then they are rifled, and after that finish lapped. Kreiger used to cryo treat at the beginning of their process, before drilling, but when I checked recently I was told that the current quality of the steel that they are getting gives as good or better results in the drilling process as when they were cryoing, which they have discontinued. As far as I know, no cut rifled barrel manufacturer stress relieves their barrels, because the process does not induce stress in the metal.

One other factor can influence the stress level in contoured barrels. A small high grade button process barrel maker that I know limits the number of barrels that he contours with a given carbide insert edge because he has observed negative effects from using an insert that has dulled beyond a certain level.

I have a friend that uses lead laps to measure interior dimensions of barrels. Early on in his fitting tuners to his barrels he could feel a very small constriction (something like .0001) in the area where he cut the barrel threads for the tuner. At my suggestion he switched to a very sharp HS steel cutter and that eliminated the issue. The effect was so small as to be undetectable by most means either by measuring the barrel or looking at targets. My friend uses cut rifled barrels of the highest quality.

 

[gunsandgunsmithing]

So what happens when we set 60,000+ psi in motion, inside a bbl? The bbl expands and as pressure drops, it expands less. A natural "choke." How about the bullet? It certainly expands(obturates) to fit the bore, so becomes tighter as the bore expands less, further toward the muzzle due to lower pressure.
I do totally agree about proper stress relief being critical and that if/when a bore expands after cutting, it is also very much dependent upon how much material is removed/left. IOW, taking a 1.25 down to 1/2-28 may well expand more than a 1.250 down to say .875 or .750, all else equal. The obvious question is not so much "if" it grows but how's it shoot....or should be.
The end result can vary by bbl maker as some premium makers do a post machine stress relief while others do not. Dimensions can and do change during heat treat and potentially during stress relieving. The trick is knowing how much and accounting for this change while making the bbl to attain desired "finished" dimensions after final heat processing. Most or all cut bbl makers do not do a post machine stress relief, because the process induces less stress. Same logic applies though...If properly stress relieved post machining, there will be less if any stresses left to cause the bore to expand when cut, assuming good machining practices. Bottom line, if a cut bbl doesn't move due to less stress induced, a properly stress relieved bbl won't move either.
Not talking factory or cheap bbls here, but premium button and cut bbls. Again, how's it shoot?

 

[urbanrifleman]

Again, how's it shoot?

Nobody knows.

 

[LVLAaron]

The best shooting gun I have, is a cut rifled barrel with a 1/2 inch thread. I can insert a gauge pin in the end of the barrel... to the shoulder of the thread.

Do with that what you will.

 

[Coyotefurharvester]

I don't worry about at all. Since running suppressed all the barrels have shot better, don't care why just enjoy they do.

 

[oliver88]

Most button barrel makers perform a stress relief cycle as part of the manufacturing process and most cut barrel makers rely only on the steel mill.


This is from my own experience and I will share what I have learned.

I have tested barrel steel from France, Germany, Slovakia and the USA.

I have concluded that all barrel steels have some amount of residual stress in it from the mill. It is a product of the rolling process at the mill. I can find it by carefully measuring the springback in the material with an Edmunds Accu-Touch air gage unit running XX standards.

Yes, the steel mills run the material through stress relief cycles but this is done in a production environment…. 40,000 lbs at a time in a rail bottom furnace.

Production means that they probably shorten the cycle any time they can to increase productivity.

40,000 lbs at a time means that each bar will have inconsistent results within each bundle. The bar stock ends are yet another story.

This residual stress is why cut barrels are normally contoured prior to reaming/honing and rifling. Think about it… would it not be easier to rifle and lap everything as a cylindrical blank ahead of time and then just contour and ship? Cut barrels are not done this way for a reason.

As a button barrel maker I have developed my own pre-machine stress relief cycle on the material followed by a long soak post-machine cycle. From what I have learned I wouldn’t make a cut barrel without a stress relief cycle.



Something else that I have learned.

The less stress that is in steel the more that it will ring. I have heard of old time gunsmiths listening for barrels to “ring” but I never really believed in it until I experienced it myself by accident.

I was stacking pre-machine stress relief barrel material onto a pallet one night with the shop quiet and the machines shut down. Every time that I added a piece of material to the pallet the whole pallet would ring. I never heard this ringing sound before I started doing a pre-machine stress relief cycle on the metal.

Another thing that I have noticed is that the rack in my stress relief furnace rings. I know that it had stress in it at first because I welded it up myself and I had to beat it into position with a sledgehammer because it twisted after I tacked it up. Now that it has been through many stress relief cycles it will ring for over 5 minutes. It sounds like a big church bell if I tap it with a small brass hammer.



I know that it is old school but the “ring” test still works especially on bar stock material.

I can cut 3 pieces of barrel stock out of the center of a 12’ or 17’ bar from any steel mill and then drill a small hole perpendicular through the ends of them so they can be hung up like a wind chime.

Piece #1 Hang it up just as it came from the steel mill with nothing else done

Piece #2 Material ran through my stress relief cycles

Piece #3 Material ran through my stress relief cycles and then a cryo cycle

When I tap these pieces with a small brass hammer I can hear three very distinct music notes.

The idea of ringing cryo material came from my cryogenic contractor because he was running brass music instruments for the Indianapolis Philharmonic Orchestra. The musicians can hear a tone difference after cryogenic treatment because cryo changes the crystalline structure of the metal.

This may be more of a factor than we think as we all chase tune and harmonics.

 

[gunsandgunsmithing]

Most button barrel makers perform a stress relief cycle as part of the manufacturing process and most cut barrel makers rely only on the steel mill.


This is from my own experience and I will share what I have learned.

I have tested barrel steel from France, Germany, Slovakia and the USA.

I have concluded that all barrel steels have some amount of residual stress in it from the mill. It is a product of the rolling process at the mill. I can find it by carefully measuring the springback in the material with an Edmunds Accu-Touch air gage unit running XX standards.

Yes, the steel mills run the material through stress relief cycles but this is done in a production environment…. 40,000 lbs at a time in a rail bottom furnace.

Production means that they probably shorten the cycle any time they can to increase productivity.

40,000 lbs at a time means that each bar will have inconsistent results within each bundle. The bar stock ends are yet another story.

This residual stress is why cut barrels are normally contoured prior to reaming/honing and rifling. Think about it… would it not be easier to rifle and lap everything as a cylindrical blank ahead of time and then just contour and ship? Cut barrels are not done this way for a reason.

As a button barrel maker I have developed my own pre-machine stress relief cycle on the material followed by a long soak post-machine cycle. From what I have learned I wouldn’t make a cut barrel without a stress relief cycle.



Something else that I have learned.

The less stress that is in steel the more that it will ring. I have heard of old time gunsmiths listening for barrels to “ring” but I never really believed in it until I experienced it myself by accident.

I was stacking pre-machine stress relief barrel material onto a pallet one night with the shop quiet and the machines shut down. Every time that I added a piece of material to the pallet the whole pallet would ring. I never heard this ringing sound before I started doing a pre-machine stress relief cycle on the metal.

Another thing that I have noticed is that the rack in my stress relief furnace rings. I know that it had stress in it at first because I welded it up myself and I had to beat it into position with a sledgehammer because it twisted after I tacked it up. Now that it has been through many stress relief cycles it will ring for over 5 minutes. It sounds like a big church bell if I tap it with a small brass hammer.



I know that it is old school but the “ring” test still works especially on bar stock material.

I can cut 3 pieces of barrel stock out of the center of a 12’ or 17’ bar from any steel mill and then drill a small hole perpendicular through the ends of them so they can be hung up like a wind chime.

Piece #1 Hang it up just as it came from the steel mill with nothing else done

Piece #2 Material ran through my stress relief cycles

Piece #3 Material ran through my stress relief cycles and then a cryo cycle

When I tap these pieces with a small brass hammer I can hear three very distinct music notes.

The idea of ringing cryo material came from my cryogenic contractor because he was running brass music instruments for the Indianapolis Philharmonic Orchestra. The musicians can hear a tone difference after cryogenic treatment because cryo changes the crystalline structure of the metal.

This may be more of a factor than we think as we all chase tune and harmonics.

Awesome info!

 

[spike-55]

Most button barrel makers perform a stress relief cycle as part of the manufacturing process and most cut barrel makers rely only on the steel mill.


This is from my own experience and I will share what I have learned.

I have tested barrel steel from France, Germany, Slovakia and the USA.

I have concluded that all barrel steels have some amount of residual stress in it from the mill. It is a product of the rolling process at the mill. I can find it by carefully measuring the springback in the material with an Edmunds Accu-Touch air gage unit running XX standards.

Yes, the steel mills run the material through stress relief cycles but this is done in a production environment…. 40,000 lbs at a time in a rail bottom furnace.

Production means that they probably shorten the cycle any time they can to increase productivity.

40,000 lbs at a time means that each bar will have inconsistent results within each bundle. The bar stock ends are yet another story.

This residual stress is why cut barrels are normally contoured prior to reaming/honing and rifling. Think about it… would it not be easier to rifle and lap everything as a cylindrical blank ahead of time and then just contour and ship? Cut barrels are not done this way for a reason.

As a button barrel maker I have developed my own pre-machine stress relief cycle on the material followed by a long soak post-machine cycle. From what I have learned I wouldn’t make a cut barrel without a stress relief cycle.



Something else that I have learned.

The less stress that is in steel the more that it will ring. I have heard of old time gunsmiths listening for barrels to “ring” but I never really believed in it until I experienced it myself by accident.

I was stacking pre-machine stress relief barrel material onto a pallet one night with the shop quiet and the machines shut down. Every time that I added a piece of material to the pallet the whole pallet would ring. I never heard this ringing sound before I started doing a pre-machine stress relief cycle on the metal.

Another thing that I have noticed is that the rack in my stress relief furnace rings. I know that it had stress in it at first because I welded it up myself and I had to beat it into position with a sledgehammer because it twisted after I tacked it up. Now that it has been through many stress relief cycles it will ring for over 5 minutes. It sounds like a big church bell if I tap it with a small brass hammer.



I know that it is old school but the “ring” test still works especially on bar stock material.

I can cut 3 pieces of barrel stock out of the center of a 12’ or 17’ bar from any steel mill and then drill a small hole perpendicular through the ends of them so they can be hung up like a wind chime.

Piece #1 Hang it up just as it came from the steel mill with nothing else done

Piece #2 Material ran through my stress relief cycles

Piece #3 Material ran through my stress relief cycles and then a cryo cycle

When I tap these pieces with a small brass hammer I can hear three very distinct music notes.

The idea of ringing cryo material came from my cryogenic contractor because he was running brass music instruments for the Indianapolis Philharmonic Orchestra. The musicians can hear a tone difference after cryogenic treatment because cryo changes the crystalline structure of the metal.

This may be more of a factor than we think as we all chase tune and harmonics.

Is this from ABC Barrels????
If so I hope there is an ETA on barrels hitting the market on a regular basis again???
stan

 

[urbanrifleman]

I don't worry about at all. Since running suppressed all the barrels have shot better, don't care why just enjoy they do.

Weight beyond the muzzle. Good to hear!

 

[Olde Man]

Wouldn't screwing and torquing any thing on to either end of a barrel tend to change its internal dimension based on the applied torque?

 

[D Coots]

The information came from Frank Green at Bartlein Barrels.

Oh, that old guy there....

 

[D Coots]

I tried some cyroed wear parts in one of my primary rock Crushers years ago. It was impossible to track the difference in wear in my application due to working in different benches in the quarry. Different abrasiveness of aggregate in each bench. So, not a good test.

Try hitting a cyroed golf ball sometime. It will definitely go further, but is similar to hitting a rock.....

Later

Dave

 

[AlNyhus]

Oh, that old guy there....

A man that actually  makes barrels.

 

[Sniperhandle]

I tried some cyroed wear parts in one of my primary rock Crushers years ago. It was impossible to track the difference in wear in my application due to working in different benches in the quarry. Different abrasive in each bench. So, not a good test.

Try hitting a cyroed golf ball sometime. It will definitely go further, but is similar to hitting a rock.....

Later

Dave

I would never have thought someone would cryo a golf ball! That's pretty funny!

 

[D Coots]

I was told they are not legal.

 

[Sniperhandle]

I was told they are not legal.

I'm sure there is no way of knowing and people do it all the time. I have been around racing people and some of the shenanigans I have heard them pull to get an edge is pretty creative.

 

[jackieschmidt]

Residual stress in buttoned rifled barrels another one of those subjects that has been discussed for decades. And over these decades, there have been those that have actually checked, with deltronic pins, the after affects of turning a substantial amount of material from the muzzle end of a buttoned rifled barrel.

I did this to a Shilen blank years ago. We cut about 1 1/2 inch from a new HV blank, gaged It with a Deltronic Pin, then turned the end down to 5/8 inch for 3/4 of an inch.
The end opened up .0002. But, not right away. It actually took overnight for the dimension to change enough to be measured.

I wrote this up on Benchrest.com some 20+ years ago, with about the same reaction from fellow Posters as now…….”well, what does that prove”?……..”Why didn’t you do five barrels”?….”Did it make a difference on the target?”

Truth is, all we were concerned with was a barrel on a Short Range Benchrest Rifle. It is general knowledge how anal we can be about everything. For 99% of all the other Rifles shot in various other Disciplines, an argument can be made that it simply does not make a bit of difference.

Now, as for Krieger Cut Rifled Barrels, I have turned them down in the same manner and they do not change within the measuring capabilities of Deltronic Pins, which are in .0001inch increments.

On the subject of Cryo Treating materials, there is solid anecdotal evidence as to its aiding In the completion of the Martensitic Transformation during the heat treating process of various materials. This comes into focus in applications where aid in machining and finished product ductility is of prime concern, particularly in low temperature environments.
Cryo treating of high stressed parts has become quite common in a wide variety of industries, from aerospace to the oil patch.

As to it’s benefits in all other aspects of metallurgy, perhaps the best that can be said is it doesn’t hurt anything.

 

[Jonnyofalltrades]

I think that the "slipping a gauge pin into the muzzle" test should be repeated after the muzzle device is torqued up. It would more than likely reverse the flaring effect, and introduce a restriction at the muzzle.
Just a side effect of using a V thread.


Time to start using buttress or square cut threads for all muzzle device thingys!