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BORE FINISH

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OLDGUNNER
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BORE FINISH

#1 Post by OLDGUNNER » Thu Mar 29, 2018 11:06 pm

http://riflebarrels.com/barrel-fouling/
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AGAIN, FOR WHAT IT'S WORTH - -
A few years ago I talked to at least a half dozen of the major barrel makers on the phone about the bore finish of their custom barrels. Maybe half of them would tell me just what kind of finish that I would get with their barrels, and the other half would not. For some reason half thought that what they would be telling was some kind of proprietary information on the bore finish - in other words the final grit finish, which they thought you should not have to be told what you would be buying, but there are people that will buy these – I wouldn’t. It’s ‘We have something to sell you but we won’t tell just what’. I say, ‘Hog Wash’.
Anyway, Daniel Lilja was one of the ones that wouldn’t say. I understand what he told me about the bore can be ‘too smooth’. I have figured out that most try for ‘about’ 800 grit (for accurate target rifles and ‘maybe’, just maybe, up to 1000 for bench-rest). But usually just 800 will work fine. And the 320 grit finish is just about a good compromise for military and hunting rifles. Because I understand this 320 grit typically allows for the about the lowest weight of the rifle. Dan Lilja told me that he would ‘guarantee’ that ‘NONE’ of his barrels would lead or copper foul – never had one so don’t know about that. Oh yes, one of the barrel makers did said that they typically lap up to 1000 grit. And one shop foreman said that they typically spend an hour making the barrel and about 10 minutes on the lapping.

But I have an FR8 that I just slugged the other day at 0.308 and would like to lap to 800 grit and use these Nosler Molly coated bullets until I get a good coating and then see if I can use un-lubed cast bullets without leading. I believe in experimenting with anything as long as it is not too detrimental or dangerous. I don’t know about the ‘carbon fouling’ as being desirable that he mentions in his article.
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Re: BORE FINISH

#2 Post by Smokey » Fri Mar 30, 2018 7:06 am

Many years ago I worked with a US M1917 (full military configuration) that had a new JA replacement barrel installed. The owner complained it shot poorly, giving 4-6 inch groups at 100 yd. The lands had very prominent machining marks left from the initial drilling of the bore. I got the same mediocre accuracy when I tried it.
I went to work with J&B bore cleaner, starting with short strokes near the breech, gradually increasing the strokes until I was finally doing the full length of the bore.
The rifle now shoots close to minute of angle with any decent ammo, and the owner is quite pleased.
Arguing with someone who denounces reason is like administering medicine to a corpse.

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Re: BORE FINISH

#3 Post by OLDGUNNER » Fri Mar 30, 2018 11:38 am

Yes, it is a plain mystery to me that more gun owners do not accept the fact the most off-the-shelf or military fire arms can usually be greatly improved by lapping the barrel, and then selecting by trial and error a custom made ammo for the each particular fire arm. Years ago on a forum I read where some guy wrote that he had no trouble getting his rifles to shoot 5 inch groups so he saw no reason to change anything with them. And for some reason the selection of a custom ammo for each fire arm is one step too big to take. I know that for some people, they are just afraid to. Or that their interest just will not take them to that next step...and I understand this is entirely okay for these people. But to me it is like someone that collects books but never reads them.
And I completely understand that some will just buy a gun and some ammo and check it out to see if it will hit that can at 50 yards and be perfectly satisfied to let it be at that and be ready for deer hunting. Yes, everyone has to have their priorities. But I still say, if one is going to bother with a hobby, then devote some interest into it.
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Re: BORE FINISH

#4 Post by OLDGUNNER » Sat Mar 31, 2018 12:04 pm

Now don’t get me wrong in that I am saying hey, “Look here at this straight scoop.” I am not – I understand that anyone can usually write what they may wish as long as it is legal. It just so happens that I, and ‘I” can do this, buy this story ‘lock, stock and barrel’. I just don’t use a lead lap . I figure that this is the least that I can I do as a no brainer. I can do it, I feel like I am doing good. I have proven to myself that it is easy to do and doesn’t cost anything but my time....and of course I think that I learn a little bit each time I do it.
Yes Smokey, as you may have found out I think that for most every serious rifle shooter, this is the least they can do. I realize that for most shooters, if it goes ‘BOOM’ they are doing just fine...and that is okay, they just don’t wish to get too wrapped up into these things. And I sure don’t either....I try to keep it at a ‘not too costly fun thing’. And if I don’t enjoy it, I don’t do it.
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Button Rifling
Button rifling was perfected during World War II when it became clear that the slower cut rifling methods of the day couldn’t satisfy the tremendous demand for barrels. The process was perfected by Remington who used the nearby facilities at Hart Barrels for its experiments during the development.

In this process, which is the most common in the U.S., a carbide "button" is passed through the bore to form the rifling. First the bore has to be lubricated. Every barrel maker has their own "secret sauce" or lube and guards its identity fiercely. A button is a somewhat football shaped carbide tool with the rifling pattern ground in relief into its surface. The button is attached to a rod and is then pulled through the bore. (Hart pushes them through instead.) As the hard button passes through, the raised rifling pattern on its surface is pressing into the softer surface of the bore and is creating the grooves in a cold forming process.

The operation is very fast, and only takes about a minute per barrel. Thus, button rifled barrels are usually less costly to produce. There are two types of buttons. One is a simple rifling button which works as just described. On the minus side, a simple button will leave burr like feathers on the edge of the lands. However, a combo unit which consists of a rifling button and a finishing button will both press in the lands and smooth their edges in the same pass.

As you might guess, pulling an oversized button through an undersized hole requires great force and creates significant stress in the barrel. As a result, it’s mandatory that button rifled barrels be stress relieved after the process. If not, all kinds of strange things including splitting down the length of the barrel is possible.

Lapping

Most premium barrels are lapped. The unanimous verdict of just about every expert in the barrel making arena is that lapping does indeed improve accuracy. Lapping accomplishes this by polishing the interior surface smoother and eliminates any tight spots in the bore.

Lapping is generally a hand operation. A rod with a handle at one end is inserted into the new barrel. Molten lead is then poured down the muzzle around the rod for a distance of around 4". The lead then hardens and the lead plug or lap is tapped out. The lap now has the perfect relief pattern of the interior of the bore. Lapping oil or lapping compound is placed on the plug which is then passed back and forth in the polishing process. An experienced person can readily feel any tight spots and then work to eliminate them to produce a near dimensionally perfect bore. Again, all this hand work costs money, so only the very top quality barrels will be hand lapped.
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Re: BORE FINISH

#5 Post by OLDGUNNER » Sat Mar 31, 2018 3:50 pm

Again, just for what it’s worth – It looks like Krieger makes his typical barrels with about 600 grit lapping finish, per his website. I have close to that, two grits, 500 and 800, along with say 170 to 1500, in Silicon Carbide. In Aluminium Oxide I have down to 0.3 Microns (Linde A). That’s a lot finer that the J&B products. Oh yes, too fine to bother with. Anyway he is saying that he doesn’t do the Button Rifling.

I went to a steel seller one time to buy some cheap Hot Roll 7/8’s bar just to make things with and he said that he had some 4140 for the same price, a dollar and a half a foot. And I said why so.....economical? And he said, “Oh I just got a good price.” I didn’t ask him where it came from, etc. He cut a six foot length into three pieces for 9 $. So I don’t know what these barrel makers pay for their 4140. Even Walmart lists it. It may be by a separate seller. I assume that it is not US made.

A lot of people think that they are wearing out their barrels by lapping. But I think that I can look at it pretty close and not notice any of that, at least I can't measure it easily...with just 'some' 500 and enough 800.
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Re: BORE FINISH

#6 Post by Smokey » Sun Apr 01, 2018 7:44 am

Thanks, a lot of stuff I didn't know.
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Re: BORE FINISH

#7 Post by OLDGUNNER » Sun Apr 01, 2018 10:27 pm

Well, this is just the way that I understand of course a very, very small bit of things. And nothing that I may say comes with any guarantee what-so-ever. Like it has been said, “If one makes no mistakes, then they are not doing much.”
When I retired and moved here 23 years ago I took a machining course at a local VO-TECH school, and then was talking to the owner one day of a little local manufacturing concern that makes parts for Muzzle Loaders - no firearms, but just some various parts to make them and other accessories. He has two or three CNC machines and other single machines with one machinist and I said that I would be gland to work here with no salary, just for the experience. He said that he saw no reason that this couldn’t be done. But...his liability insurance company was afraid to go along with this so it didn’t come to be.
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