rifling methods and wear

[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.