Barrel slugging and other questions

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gmaske

Bearcat
Joined
Jan 8, 2008
Messages
78
Location
Colorful Colorado
Can anyone tell me if this is something I can do and how to go about it? I'd like to find out what my Russian made SKS barrel is for sure. There seems to be a diffrence in bore depending on which country they were made in...China v Eastern Block. I'm going to start reloading for this rifle and want to get started right. As I understand it, 7.62 is actually .300 so what is the "CORRECT" size jacketed bullet to load? If someone knows what the Russian barrel should be that would be great! I've been looking on line and see bullets listed as .308, .310, and .311.
:shock: HELP!!! :shock:
 

Driftwood Johnson

Blackhawk
Joined
Sep 25, 2007
Messages
699
Location
Land of the Pilgrims
Howdy

I can't tell you anything about that particular caliber, but I have slugged bunches of pistol and rifle barrels.

The very first thing to do is to peek down the bore with a bright bore light and count how many grooves there are in the rifling. If it is an even number, measuring your slug is easy. If it is an odd number, it will be a real pain to get an accurate measurement. With an even number of grooves you just lay your caliper across the slug on two high points and take a measurement. With an odd number you will be measuring from land to groove and will have to do some fudging to come up with a reasonably accurate measurement for the groove diameter.

You can buy a kit for slugging that comes complete with soft lead slugs of various sizes, but I have never bothered. I just make an educated guess and select a bullet that I think is a few thousandths over groove diameter. Some will tell you that you must slug a barrel with soft lead, but I have used hard cast bullets plenty of times. I have also used a soft lead round ball that I have deformed enough so that it fills up the rifling completely. I have also heard that some use lead fishing weights, but I have not tried that route.

The basic idea is to get a slug started in the muzzle, then ram it all the way down the barrel. This works for any revolver and just about any rifle too. With a bolt action rifle you can remove the bolt and start at the chamber, but I find it easier to start at the muzzle. The important thing is to select a bullet for slugging that is just a few thousandths over groove diameter. Select a bullet that is too large and you will be whacking away for a long time before it deforms enough to get started down the bore.

I start with a short brass rod, around ten inches long or so. I jam the slug into the bore so that it stays without me having to hold onto it. I grasp both the muzzle and the short rod with one hand, leaving my other hand free to swing the hammer. Starting with a short rod is much easier to control the rod than trying to start whacking the end of a rod three feet away from the muzzle. I start out with the short rod centered on the slug, so that it is always shoving on the slug, not touching the bore. The hardest part of the process is getting the slug completely into the bore, so you want the rod short so it is easy to control. Once the slug is completely inside the bore, it offers much less resistance. I usually use a brass rod 5/16" (.312) in diameter. This allows me to use it for anything from 38 to 45. For 30 cal I would probably use a 1/4" rod. Some folks say you should lube the bore before you start slugging, but I used to do it dry all the time. These days I will run some oil into the bore, but to tell you the truth I have not noticed it make any real difference. If you are going to lube the bore before you start slugging, just moisten it, don't drench it. Too much oil will interfere with the slug completely conforming to the shape of the rifling.

When I slug a bore I do not clamp the gun in place to resist movement. I allow it to slide a little bit with each blow so that I don't transfer the hammer blows directly to the gun mechanism. With a rifle I lay a towel on the top of the bench and lay the rifle down on its side on the towel. this protects the rifle from scratching but still allows it to slide a bit with each hammer blow. With a revolver I grasp the gun horizontally by the muzzle, with the butt on the towel. This gives me good control.

I usually use an eight ounce ball pein hammer to slug a barrel. Any hammer will do, but this size seems to work well. Like I said, the hardest part is getting the slug completely into the bore. Once it is completely inside, the going gets easier. I just keep whacking the end of the rod against the slug until the slug is completely inside. Then I drive it down a few inches. I stop before the hammer starts getting too near the muzzle and change to a longer rod. The last thing you want to do is to whack the muzzle with your hammer, so keep the hammer away from the muzzle. Once you change to the longer rod, just keep driving the slug all the way until it falls out at the end. The sound will let you know when you are getting close. I let it drop onto the towel, so it does not get damaged.

A couple of other things. Slugging a bore will only tell you the tightest diameter of the bore. Some of my rifles are over 100 years old and their bores are eroded a bit near the chamber. This is fairly common with older guns that were fired with Black Powder and corrosive primers. When the slug gets near the chamber I suddenly encounter much less resistance. This tells me that I have reached a portion of the bore that is a bit larger in diameter than the rest of the bore. I just keep this in mind, knowing that when I measure the slug I will be getting a measurement of the groove diameter of most of the barrel, not the eroded part. Incidentally, this can also tell you if you have a bore with a bulge in it. Just keep track of how much resistance you are encountering as the slug travels the length of the bore.

When your slug emerges, examine it closely. The high spots on the slug will represent the groove diameter of your bore. That is what you want to measure. The low spots will represent the land diameter. You can measure the height of the high spots above the low spots for fun, but it is the groove diameter you are really interested in. Examine the slug closely. You want to see drag marks running the length of the high spots on the slug. This will indicate that the slug completely filled the rifling. If you don't see drag marks on the high spots, the slug may not have completely filled the rifling, and any measurement will be meaningless.

Some will tell you to use a micrometer when measuring a slug, but I have always found a caliper to be accurate enough. I just go down to the thousandth and interpolate any tenths if I need to. Generally, .001 is close enough with a slug. Also, don't bear down too hard with your caliper. You are measuring lead, and it is soft. Bear down too hard and you will be measuring how much your calipers deformed the slug, not how it emerged from the bore.

Hope this helps.
 

Sonnytoo

Blackhawk
Joined
Aug 4, 2007
Messages
631
Location
florida
Driftwood told you good stuff. His is the voice of experience and he sounds like he knows what he's doing. I don't do rifles but I like to mess with revolvers.
I'd like to add some things I learned from Beartooth Bullets Technical Guide, a GREAT $15 book that talks at first about bore lapping for accuracy but then gets into all sorts of graphs and tables about bullets and hardness and meplats, load development, primers, crimping, and all the good stuff.
Anyway, I got no dog in that race, but just ordered another copy for a friend last week. It's that good.
The book is by J. Marshall Stanton, who uses his .45 Blackhawk for elk.
He says to use fishing oval egg sinkers, from fishing tackle shop, pure soft lead and they have a longitudinal hole in them which is helpful. Use the hammer with a hardwood dowel to drive the slug. When you first start the slug, you will cut a "doughnut" from the slug, which is what you want.
For your .300 barrel, use size 10, 1/8 ounce and diameter of .305". If it's a mite too large, that's good. If too small, you squeeze it slightly with vise to make it a bit larger in o.d.
Size 9 is 1/4 oz and .369". Size 8 is 1/2 oz and .470". Size 7 is 3/4oz and .530". Once you get the sinker started in the bore, he actually suggests a large 5lb or heavier maul hammer and oil the barrel before you begin, using WD-40, CLP Break Free or sewing machine oil. He says a large hammer will drive the bullet down thru the bore by inertia, whereas a light hammer will obturate the slug in the bore, and stick it tight. He uses an eight-pound for his work, but I don't have anything other than regular hammers.
I gotta tell ya: get the book. You won't be sorry.
Sonnytoo
 

gmaske

Bearcat
Joined
Jan 8, 2008
Messages
78
Location
Colorful Colorado
Sonnytoo
Been busy working on my SKS so I haven't been around. I picked up your tip on the fishing sinkers elsewere. I'll have to check in to that book.

I'm pretty much done with getting a scope mounted on the rifle. I put an NcStar 3x-9x 42mm scope on the rifle. This scope is real compact and has a 2" eye relief so I had to move the scope back quite a bit. This took a little bit of "Southern Engineering" but it really solved any worries about spent brass hitting it. If the weather holds I'll be sighting it in this weekend.
 

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