Pattern In Bore - What Is It?

[BoydAllen]

Fellows, with a poor, rough reaming job and a button rifling process, and for that matter hammer forging, the pattern tool marks are in both the lands and grooves. The only situation where they are removed from the sides of the lands and the bottoms of the grooves is when the rifling is cut. I once had an NOS Springfield barrel that had been cut rifled. Close examination of the tops of the lands showed reamer marks that looked like microscopic acme threads, all the way down the barrel. Many factory barrels have all sorts of defects that look as bad as they are when viewed with a 20X bore scope. That is why, many years ago, I built my first rifle with a match chamber and a lapped Hart barrel. It solved all of those problems, and was worth every penny. I see a lot of fellows that have quite a bit of money invested in factory rifles that will never perform to a consistently high standard. IMO they would be better off selling a few and putting the money into one, well built rifle. For someone who has never had an excellent rifle the difference is just amazing. All of a sudden you discover that you are a much better reloader and shooter than you would have ever imagined. The best barrels are lapped or honed after reaming, and lapped again after rifling.

 

[msinc]

What is the choke for..

You want the bore slightly tighter towards the muzzle for accuracy...just like the muzzle crown being so important...it is the last thing to touch the bullet before it is set free and on it's way. Imagine how inaccurate a barrel would be if the last two inches of the bore got looser!!! Each bullet would be free to head off in it's own different direction.
As far as tooling marks in OEM barrels...I see them in a lot of aftermarket or custom barrels as well. Shilen match grade, Douglas XX and many others will have some tool marks. They are not bad and don't seem to affect accuracy though.
Years ago, Savage had some of the best looking factory barrels out there. You will not see tooling marks in a Lilja, Pac-Nor super match, Shilen "select" of any of the other so called "premium" barrels and you pay for it too.

 

[msinc]

I meant button chatter. But something caused those perfectly regular steps.
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The feed rate was too fast and the lubricant wasn't high enough pressure type. The manufacturer raced to get as many barrels done as possible...this is the unfortunate by product of a capitalist society...my money will always be more important than your "whatever I am selling you." It is not vibratory chatter like when turning an unsupported bar on a lathe, those little perfect spaced steps are tooling marks. Spin the bar faster and feed slower and they go away, but you don't get to sell as many barrels!!! Those marks are also not the button "skipping" or chattering either...make no mistake, a button either proceeds smoothly down the bore or it seizes and locks up. When that happens you throw the entire mess away and start over.

 

[BoydAllen]

I have seen plenty of evidence that in some Savage barrels, that were button rifled, the button did not contact the tops of the grooves, leaving the finish from reaming. I even had a conversation with a retired Savage engineer about this. Trying to make a $20 barrel shoot like a $600 barrel is generally a loosing battle, but if you get lucky, sometimes you can get a lot for your money.

 

[Brians356]

The feed rate was too fast and the lubricant wasn't high enough pressure type. The manufacturer raced to get as many barrels done as possible...this is the unfortunate by product of a capitalist society...my money will always be more important than your "whatever I am selling you." It is not vibratory chatter like when turning an unsupported bar on a lathe, those little perfect spaced steps are tooling marks. Spin the bar faster and feed slower and they go away, but you don't get to sell as many barrels!!! Those marks are also not the button "skipping" or chattering either...make no mistake, a button either proceeds smoothly down the bore or it seizes and locks up. When that happens you throw the entire mess away and start over.

I believe you about the button chatter, thanks for the explanation on the reamer feed rate and lube. Combined with Boyd's and others' remarks, this is starting to make sense.

Now, attached is a new photo I took tonight showing a relatively huge chunk missing out of a land. How does that happen? Notice also the adjacent trench in the groove. Seems like flaw or void in the metal caused this. Notice that this is away from the bad "railroad tracks" section, the adjacent lands and grooves are relatively smooth. Always learning ...
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[savagedasher]

I believe you about the button chatter, thanks for the explanation on the reamer feed rate and lube. Combined with Boyd's and others' remarks, this is starting to make sense.

Now, attached is a new photo I took tonight showing a relatively huge chunk missing out of a land. How does that happen? Notice also the adjacent trench in the groove. Seems like flaw or void in the metal caused this. Notice that this is away from the bad "railroad tracks" section, the adjacent lands and grooves are relatively smooth. Always learning ...
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View attachment 982715

 

[savagedasher]

If the checking i did is correct buttons were never used. Hammer forged barrels the metal is hammer forged over a mandrill . Early went done cold with a cnc press.
They were hot forged every time the hammer hit it would moves small amount. If the mandrill had a flaw it would engrave the flaw marks in the bore . Larry

 

[msinc]

If the checking i did is correct buttons were never used. Hammer forged barrels the metal is hammer forged over a mandrill . Early went done cold with a cnc press.
They were hot forged every time the hammer hit it would moves small amount. If the mandrill had a flaw it would engrave the flaw marks in the bore . Larry

It will also still show whatever tooling marks or flaws were in the bore before the hammer forging process. Imagine having a flat piece of steel...you take a graver and cut a small line in the surface. Now take this piece of metal and put it in a big hydraulic press and press it until that spot is completely smooth...you will still see and maybe even feel some of the line that was cut into it. The surface has been "pressed" smooth because the steel moved some, but the line {or more properly what's left of it} will still be visible. Same effect on the inside of a bore when either hammer forging or button rifling...either one are really just both a method of "pressing" in the rifling as opposed to cutting it. Tooling marks that are very slight will get completely smoothed over but still seen, those that are worse end up looking like the OP's barrel.
One of the big advantages of cold hammer forging a barrel is supposed to be that the mandrel can be manufactured to be perfectly polished and dead on twist, so there should be zero marks or flaws on the mandrel to get imposed into the bore.

 

[shortgrass]

Looks like lots of speculation here from those who will never make a hole, that has a finish requirement, any deeper than 6" or so. A cut or button barrel that has 'problems' during manufacture won't be "thrown away", they'll be bored/reamed to a larger size. Steel costs too much to just "discard the mess and start over". I see many older Remington barrels that look just like the pics in this thread. They were hammer forged. I personally don't care what contortions a barrel maker goes through, as long as I can keep getting great shooting barrels that foul little. Keep up the guessing, you must not have much of anything else to do.

 

[Cold Bore]

.... but I could get about 3/4 MOA out to 200 yards with 140-gr BTs.

If I'm getting 3/4 MOA accuracy, out of a 40+ year old factory hunting rifle, I'm really not too concerned about how things might look inside the bore.

I keep saying.... these borescopes are causing all sorts of needless hand wringing and heartburn.

 

[Eddie Harren]

If I'm getting 3/4 MOA accuracy, out of a 40+ year old factory hunting rifle, I'm really not too concerned about how things might look inside the bore.

I keep saying.... these borescopes are causing all sorts of needless hand wringing and heartburn.

But, look at all the "Experts", on barrel making technique, that have been created. I have learned more, from this thread, than I ever did by hanging out with Spencer and actually seeing barrels being made.

 

[msinc]

Looks like lots of speculation here from those who will never make a hole, that has a finish requirement, any deeper than 6" or so. A cut or button barrel that has 'problems' during manufacture won't be "thrown away", they'll be bored/reamed to a larger size. Steel costs too much to just "discard the mess and start over". I see many older Remington barrels that look just like the pics in this thread. They were hammer forged. I personally don't care what contortions a barrel maker goes through, as long as I can keep getting great shooting barrels that foul little. Keep up the guessing, you must not have much of anything else to do.

And you make barrels for....?????? My "specualtion" is that you have never made a barrel in your life and you don't like it when someone knows more than you. If you get a button stuck in the bore of a blank while pulling it you throw the whole mess away and start over. period, end of story. If a tungsten carbide button is seized in a bore it pulls no further. It cannot be drilled out and it is not worth the time to try. It isn't even worth trying to recover the button because invariably it will sustain damage and again end up being a waste of time.

"all ya gotta do..." "simple, just take it out and rebore it..." who is guessing????

Not sure what your problem is pal, if you don't like what I write, or it goes against your guesses as above then don't read my posts and stay exactly as you are right now.

 

[Rustystud]

What is the choke for..

Gas pressures increase as the bullet passes down the bore. Better Barrels tighten up .0001"-.0003" to contain expanding and to better control the spin of the bullet.
Nat Lambeth

 

[BoydAllen]

A friend who competes and who slugs (Actually he casts a lap in the bore.) most every barrel that he is trying to diagnose, or is going to chamber tells me that he would never want a barrel that had more than .0001 choke near the muzzle. Also, someone that I just spoke with who has a very good record winning short range benchrest matches tells me that he does not want any choke, but prefers a parallel bore. He is a highly regarded gunsmith. As a matter of fact, the pressure in the bore, just before the bullet exits, is a lot less than when it is when the bullet is a few inches from the breach. Getting a good fit between bullet and bore can be critical if the best accuracy is required. Some years back, I toured the Pac-Nor plant, it was very interesting. In the past, I have spoken with various barrel makers about how their barrels are made, and for that reason I feel that I am familiar with how cut, button, and broached barrels are made. As far as hammer forging goes, I have done some research, including watching some videos. On reaming (which is done after deep drilling) the way that the reamer is made and sharpened is critical to a good finish, and depending on the quality of the barrel, it may be done more than once to gradually approach the final dimension and finish. One of the more interesting developments in barrel making is the new Sunnen honing machine. Bartlein worked with them refining the first prototype. Since then several barrel makers have bought them. I spoke with Frank Green at some length about this process.

 

[stansrifles]

Gas pressures increase as the bullet passes down the bore. Better Barrels tighten up .0001"-.0003" to contain expanding and to better control the spin of the bullet.
Nat Lambeth

Are you talking about rimfires or center fire barrels.

 

[savagedasher]

Are you talking about rimfires or center fire barrels.

Wouldn't the pressure be the highest at the time of ignition and be less at the muzzle?
I thought the choke in the barrel was to guide the bullet better from the the wear of the rifling to bullet. Larry

 

[butchlambert]

Shortgrass, Eddie, and Stan plus a couple others. Don't you feel smarter after reading this thread?
Deathstar used LW blanks which were a precipitating hardness steel. Kinda like 17-4. Deathstar's process worked on medical equip., but never made a barrel shoot competitively.

 

[stansrifles]

Gas pressures increase as the bullet passes down the bore. Better Barrels tighten up .0001"-.0003" to contain expanding and to better control the spin of the bullet.
Nat Lambeth

Really .

 

[stansrifles]

Shortgrass, Eddie, and Stan plus a couple others. Don't you feel smarter after reading this thread?
Deathstar used LW blanks which were a precipitating hardness steel. Kinda like 17-4. Deathstar's process worked on medical equip., but never made a barrel shoot competitively.

I love it butch this is good stuff.

 

[shortgrass]

Shortgrass, Eddie, and Stan plus a couple others. Don't you feel smarter after reading this thread?
Deathstar used LW blanks which were a precipitating hardness steel. Kinda like 17-4. Deathstar's process worked on medical equip., but never made a barrel shoot competitively.

Ya',,,, I feel a lot smarter. It gets easier to tell who's actually done much of anything and who hasn't. I have never made a barrel, but deep hole drilling with a gundrill and reaming with a tube reamer are not exclusive to making rifle barrels. What is it Eddie says?,, "better than the funny papers"......