lapping a barrel

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wtnhunt Monster Buck

wtnhunt

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Re: lapping a barrel

Here you go, copied this from the bluelk ml chapters for you:

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Chapter 6: Lapping your barrel

We are now at the point where you have gotten your rifle to shoot where you point it. What we need to do now is modify the barrel so as to make sure that your accuracy increases and your bullet travels faster down the bore. What we are going to do is "lap" the barrel. This is a major job so get the following items all rounded up before you start. Get the following items: 2 new brass bore brushes, a hand full of patches (I cut mine from an old t-shirt and wash them when they get dirty), 2 or 3 bore swabs, a small can of automotive valve lapping compound (fine), bore solvent, a few cotton balls, and some teflon based lube. Make sure it is teflon based. Also, a little liquid refreshment for you helps.

If you have a vice take the barrel out of the rifle. If you don't have a vice leave the barrel in the rifle, but get a buddy, wife, or kid to help hold the rifle. If you have a vice open it up and pad the jaws with about an inch of rags to cushion the barrel so that you don't scratch it. Close the vice tight enough to hold the barrel still. If you don't have a vice put a human on the stock end of the rifle and tell them to hold it tight. Put a bore BRUSH on your ramrod, wrap it with a patch, and apply a liberal amount of lapping compound all around the patch. What you are going to do is run that brush/patch compound down the barrel and remove any manufacturing burrs off of the edges of the lands, and remove any high spots. If you want to see how bad the situation is before you start, put a cotton ball on a worm jag and run it through the bore. Look down the bore and see how many cotton fibers are stuck in there. Even if you don't see any you still want to lap the barrel for reasons that will become obvious.

Push the ramrod down the barrel and pull it out. That is 1 stroke. If you had any amount of cotton fibers stick in the barrel you are going to do 100 strokes. If you did not have ANY stick to the barrel you are going to do 50 strokes. After about 10 or 15 strokes you will need to change the patch and apply more lapping compound. After you have completed this step clean the barrel THOROUGHLY with a bore brush because you will have lapping compound in the grooves. Put some solvent on a bore swab and clean it some more. After you have cleaned it run another cotton ball down the bore. Do you see any fibers? If you do repeat the lapping process for another 50 strokes. Clean it again and run another cotton bore down the barrel. If you see any fibers repeat the lapping process for another 25 strokes. Okay, now you can run a cotton ball down the barrel without having any fibers stick, and when you look down the barrel it is shinier than you know what. Make sure the barrel is as clean as is humanly possible.

A mistake that some people make is to mount their ramrod in a drill motor and spin the ramrod down the barrel. DON'T DO THIS or you will round off the edges of the lands and you will lose your gas check on your bullet. Just let the bore brush/patch combination rotate normally as you run it down the barrel.

Change out the bore brush for a BORE SWAB and saturate the swab with the Teflon lube. Use lots. Now, if you had the barrel in a vice take it out and put it in a bucket of REAL HOT water. If you had someone hold the rifle take the barrel out of the stock and do the same thing. Hold onto the barrel with a thick glove or some rags during this process. Get THE ENTIRE barrel HOT from end to end! Absolutely saturate the inside of the barrel with the Teflon based lube. As the barrel cools it will suck the lube into the pores of the steel and seal it in. The more lube you use the better. Let the barrel cool completely. Take the clean bore swab that you have left and clean the excess lube out of the barrel. Look down the barrel. I suggest you wear some sunglasses when you do!!

What you have just done is what every professional target shooter does to his rifle. You have increased the speed of your bullet anywhere from 100 to 200 feet per second, and made the rifle more accurate. How have you made it more accurate? Remember one of the basics of ballistics. The explosion of the powder behind the bullet produces gas which pushes the bullet out of the barrel. The more gas you can retain behind the bullet the faster the bullet travels. The faster the bullet travels, in combination with the twist of the barrel the more accurate your rifle is. All of those chatter marks, burrs, and high spots cut into the obfligated (expanded)base of the bullet, or patch, and allowed gas to escape around the bullet while it was traveling down the barrel. You have eliminated that from happening by lapping the barrel.

After the barrel has cooled completely, run a patch down the barrel with a light coat of oil, reassemble the rifle and have some liquid refreshment. I have found that barley pop tastes real good right about now. Once a year repeat the teflon based lubrication portion. I also apply the teflon based lube to the OUTSIDE of the barrel while it is hot and it seems to help keep the barrel from rusting.

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