rifling methods and wear

[konrad]

I was in a shop the other day and the fellow behind the counter made a comment I thought interesting if not accurate.

He said brand X rifle was button rifled and as such would wear out faster than a more expensive rifle.

It has been my understanding that broach and button rifling both cut lands and grooves into the bore. One does the job with successive cutters and one does the job all at once.
For the life of me, I can not fathom the logic behind this fellow’s comment.

Is there a difference in throat quality between the two rifling methods that would lead to faster throat erosion?

My feeling was the young man was merely full of beans and not information.
I was dumb struck at the time and did not attempt rebuttal; however, I think the issue needs resolving in my own mind.

Help!

[madmack76]

the only thing i can think of is that a buttoned rifled is easily damaged at the tip but don't know for sure my

[Huntbear]

Unless you shoot 10,000 rounds a year through either barrel, you have nothing to worry about.  Look at all the pre 64 model 70s out there.  They are about 40 years old now.  Unless they have been abused, they still shoot.  Look at Enfields, 03A3s, etc..  Go ahead, I think you should try to shoot out a barrel.  I hope ya have a lot of money for ammo.   

[demontang]

The only thing that you might see is a broch cut barrel will be more accurate. what the barrel is made of would effect its life more then how the rifling is cut.

[AWS]

Here's and interesting read on barrels.

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

I don't think any manufacture is making production rifles with cut rifle barrels.

AWS

[Bofire]

 :)I shot out a 7mm mag barrell in about 4 years. Have seen a number of shot out barrels. Even in the lowly 223 seen shot out barrels. None of them took anywhere near 10,000 rounds. I have seen newly barrelled rifles in certain cartridges showing accuracy degradation in less than 300 rounds.
Carl

[demontang]

Yes there are few broch cut barrels out there of factory rifles. Most are button rifled, and the round you shoot has more to do with barrel life them anything.

[Huntbear]

:)I shot out a 7mm mag barrell in about 4 years. Have seen a number of shot out barrels. Even in the lowly 223 seen shot out barrels. None of them took anywhere near 10,000 rounds. I have seen newly barrelled rifles in certain cartridges showing accuracy degradation in less than 300 rounds.
Carl

But was it due to Throat erosion due to hot loads?  Or did the rifling wear out???   Throat erosion is an easy fix, take a turn or two off the barrel, and re cut the chamber.  A lot cheaper than a new barrel.

[Bofire]

if the throats eroded those riflings are wore out.?
Carl

[shaneman153D]

Unless you shoot 10,000 rounds a year through either barrel, you have nothing to worry about.  Look at all the pre 64 model 70s out there.  They are about 40 years old now.  Unless they have been abused, they still shoot.  Look at Enfields, 03A3s, etc..  Go ahead, I think you should try to shoot out a barrel.  I hope ya have a lot of money for ammo.   

A small bore and a lot of powder (.223WSSM, 7mmRUM, etc) will surely burn a barrel out in waaaay less than 10,000 rounds.  Shooting the lightest bullets you may not last 1000.  I doubt with this being a hunting forum it happens very often to the members here, but it happens.

If you google "barrel life calculator" there are a lot of good programs out there that factor in powder heat, pressure, dia, moly/chrome, etc and can "predict" when you will see accuracy degradation.  I always run this program when picking out a new powder.  http://accurateshooter.wordpress.com/2009/09/23/handy-excel-formula-predicts-useful-barrel-life/

I just bought a Remington 5R in .308 because of this.  I was going to get a Sendero in 7UM, but I figured my first LR rig will likely see a lot of rounds so I bought this "practice" gun instead.

[high country]

most will never wear out the barrel, just the throat. in sane level non overbore rounds it takes a lifetime for the average shooter, or about 9 months for a loonie

[JackOfAllTrades]

 

if the throats eroded those riflings are wore out.?
Carl

No.  An eroded throat could only mean the first .1-.2".  That does not mean that the rest of the barrel rifling is worn out. It could mean that the rest of the barrel rifling is soon to follow, but not necessarily. -And 'soon to follow' could be another 50% of the amount shots it took to erode the throat in the first place. The throat almost always wears first. As someone posted earlier, just turn the barrel face down enough to ream out the erosion and set new head space, a rifle barrel will be given new life.

I've known people over the years that when their favorite rifle started to lag off in the accuracy department, they'd just sell the rifle. It's actually a lot cheaper just to turn down and re-chamber ream a barrel or install a new barrel now'a days. There are lots of choices.

-Steve

[Bofire]

 :)Yep I agree Steve, I do not think anyone has ever worn out the rifling in an entire barrell, but if any of the riflings are worn out the accuracy is worn out, of course the throat wears first, it is hotter and higher pressure there. I did not say there were no cures, ie: shortening the barrell, rechamber, rebarrell.
  Carl

[JackOfAllTrades]

Brings to mind the less sought after deep two land cut O3-A3 and M1 barrels of years past for the more shallow four groove barrels in latter years. I have a four groove 03-A3 that still shoots just about MOA. I'll bet there's 25,000 thousand rounds been down that barrel. In that article, there's slight mention of the shallow cut lands, A.K.A. Marlin Micro Groove. My old Marlin 39 with micro cut barrel never ceases to amaze me with it's accuracy when compared to other .30 carbines of the same era. While many target barrels aren't quite micro groove rifling, they do wear out faster. Most people should never need to worry about this with a hunting rifle.

-Steve

[high country]

Brings to mind the less sought after deep two land cut O3-A3 and M1 barrels of years past for the more shallow four groove barrels in latter years. I have a four groove 03-A3 that still shoots just about MOA. I'll bet there's 25,000 thousand rounds been down that barrel. In that article, there's slight mention of the shallow cut lands, A.K.A. Marlin Micro Groove. My old Marlin 39 with micro cut barrel never ceases to amaze me with it's accuracy when compared to other .30 carbines of the same era. While many target barrels aren't quite micro groove rifling, they do wear out faster. Most people should never need to worry about this with a hunting rifle.

-Steve

as most will fail to recignize, it takes very little to get the bullet to spin. the biggest issue is decreased pressures that must be adjusted for......IMO

[shaneman153D]

The throat eroding .1-.2" is a bigger deal than one might think.  By moving my bullet .112" closer to the lands on my .308, it went from a Sub .75 MOA gun to .3 MOA gun.  If you reload, you can load a longer OAL when the throat goes, but you can only do it for so long.

You can wear out the rifling all the way through.  I slugged the barrel on my M91/30 and it measured .313 (Supposed to be .311).  That gun is a 1941 production so that will give you an idea of how long it takes.   

[Cascader74]

As far as rifling erosion vs throat erosion when in the Marines as an armorer I replaced far more barrels due to rifling erosion than throat erosion. Of course military rifles will wear out faster than hunting rifles by mere number of rounds fired. Most are estimated to have a barrel life of 10,000 ends at production but that's arbitrary you could see far more or less than that.

[klickitat]

This is actually a huge topic that will never fully get covered here on this forum. It is a life time study if you want to understand it fully.

A couple little things to think about.

#1 Button rifling is an easier and cheaper way of imparting rifling in a barrel. The problem was that in the early days the steal was not as consistent as it is today and as such different parts of the barrel would not act consistently as the button was pulled through. This caused barrels to have loose and tight spots. This is why broach cut barrels where considered better for the longest time.

#2 Broach cutting a barrel is extremely accurate if done right through even inconsistent steal. This is because it removes material rather than just pushing indents into the steal like button rifling does.

Now the rub; broach cutting has to be done slowly and can not be rushed by taking too big a cut at one time and the tooling has to be sharp at all times. They also need to be hand lapped. This is very expensive and barrels are easily messed up when doing this.  With today's steal, I do not think that 99 out of a hundred people are ever even going to notice a difference.

BTW; a broach cut barrel will erode and loose accuracy faster than a button rifled barrel if it is not hand lapped. This is because the sharp corners of the broach cut rifling will burn. Hand lapping deburs the edges and polishes them out making them a bit more resistant to burning.

[FC]

As far as rifling erosion vs throat erosion when in the Marines as an armorer I replaced far more barrels due to rifling erosion than throat erosion. Of course military rifles will wear out faster than hunting rifles by mere number of rounds fired. Most are estimated to have a barrel life of 10,000 ends at production but that's arbitrary you could see far more or less than that.

When I was issued my used M16A1, it was the most worn out rifle I had ever fired, I handed it back about 15,000 rounds later and while it was definitely in need of a bolt it was still an accurate rifle if you flopped the upper receiver to the left before taking your first shot. To date that old beater is still the most worn out rifle I have ever fired, I only saw the barrel glow a few times   but have no idea what it had been through before I got it. From what I've seen people do to those things I would think you would need to fire 10,000 off in less than an hour to do the barrel any real harm although you would have to pour oil into it liberally to keep it running after the first 500 or so.

I am guessing that most of the erosion is caused by incessant cleaning.

[PA BEN]

I wished he talked about HAMMER RIFLING. He said all new Rugers are hammered. I have a new Ruger 7mm rem mag.

[konrad]

Hammer forged barrels are tubes pulled over a mandrel with the rifling pattern on the outside of the mandrel. Then a series of hammers strike the barrel steel around the mandrel so hard that the inner surface of the barrel takes on the shape of the mandrel’s exterior surface.

I read that GPW of Steyr, Austria was the first company to manufacture machinery that could mass produce Hammer forged barrels, with the chamber and variable barrel profile.
As with so many other things, quality control up front affects the quality of the finished product. If the barrel blanks are of good steel, the mandrel has well done rifling and the blank has a smooth interior finish prior to the forging process, a very acceptable hunting barrel may be produced.

My Rugers have all been excellent performers when the load has been tailored to the rifle. I can’t speak to accuracy using factory produced ammunition except in the Mini-14 and the 14 is no match platform.

[PA BEN]

Factory loads are ok, they w/work for hunting. My hand loads have a tighter group.