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Old July 6, 2012, 09:46 AM   #1
Prof Young
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Slug the bore?


In another thread someone suggested that I "slug the bore" of my Henry 45 colt.

So I took my Henry out of the safe and punched it good. Hurt my hand but the accuracy didn't change. :-)

What does "slug the bore" mean and how do I get it done?

Live well be safe.
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Old July 6, 2012, 10:03 AM   #2
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It means to push a soft slug just over groove diameter down it to measure the groove diameter. Since you aren't matching slug to throat dia to groove dia, this maybe a waste of time.

I would measure groove dia at the muzzle with calipers and then try +0.000, +0.002, +0.004 cast bullets and see what it likes.

Another trick is to try something like Bear Creek Supply bullets which are soft, but coated lead bullets.

BTW, all this works for reloaders only.

I would also try different powder burn rates. With a rifle length barrel, slower burn rates might yield best accuracy.

I'm assuming this suggestion was done to improve accuracy??
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Old July 6, 2012, 11:08 AM   #3
maggys drawers
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Get an egg sinker from somewhere that sells fishing supplies. Many are not pure lead these days, but usually say "environmentally safe" or some other tree hugger phrase if they aren't. If I remember right, a 3/8 oz sinker is the right size for 44/45 bores. Sinkers work better than a bullet because the hole in the middle gives the slug somewhere to collapse to without distorting.

Oil up your bore with a well oiled patch and tap the sinker into the muzzle with a wood mallet or other soft faced hammer (saves dinging up the barrel with a steel hammer). Use a brass rod close to the diameter of your bore to drive the slug down the length of the barrel and out the other end. With a .45 I would use a 3/8 rod. These are available at welding supply stores. I've used a hardwood dowel, but I hear if the dowel splinters, the splinters will wedge the slug in the bore and then you got real problems.

Measure the groove impressions on the slug (they are reversed from your bore, so they will make the widest raised areas on your slug) with a micrometer- this will give you a much more accurate reading than measuring with calipers, and accuracy is the whole purpose of doing this. Hopefully your barrel has an even number of grooves- it makes measuring much easier. Find the largest diameter of your slug.

The cast boolit you are shooting should be .001 to .002 over measured slug diameter.

The real trick is
1) have the bore well lubricated so the slug will drive through easily
2) use a pure lead sinker

It isn't difficult to do, but rounding up the right stuff to do it makes all the difference. It will give you a little "pucker factor" the first time you start hammering on your gun's muzzel- just use the soft face hammer to avoid any damage to your gun.
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Old July 6, 2012, 12:32 PM   #4
chris in va
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I couldn't find an egg sinker that fit my bore so just oiled up my barrel and stuffed an unsized lead bullet through.

Maybe I was doing it wrong, but I was told to do it through the chamber end.
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Old July 6, 2012, 01:43 PM   #5
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Using an unsized bullet is ok, as long as you know it is definitely larger than your bore. If it is slightly smaller (you probably won't KNOW this) then it will still push through the bore without completely "filling" the grooves, giving you a slightly smaller than actual diameter measurement.
A trick you can use is to take the unsized bullet and squeeze it slightly in a vise to make the bullet a little "fatter" than normal, then drive it through.

Driving it through from the chamber end is the best way, in the event that your muzzle is tighter than the chamber end.
I always felt that if I got to the point where I thought it was time to bury my firearms, it was actually time to pick them up..
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Old July 6, 2012, 09:39 PM   #6
Prof Young
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Okay, I think I understand. There is so much detail to consider when loading for accuracy. Lots to learn. I'm thinking I need to dig out my reloading book do more reading.

Live well, be safe
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Old July 6, 2012, 10:27 PM   #7
F. Guffey
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it is possible to 'slug' a bore, comes under the heading of methods and techniques, in my opinion a slug that is smaller than the bore is as good or better than most methods, the problem? is in the details, the weak pass out and the strong get weak, then there is another method, it is assumed by bore checkers the slug determines the diameter of the bore, slugging the bore determines the smallest diameter of the bore, slugging the bore does not determine the largest diameter of the bore, then, there are more details.

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Old July 7, 2012, 12:30 AM   #8
Ideal Tool
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Hello, prof young...Heed what F. Guffey said..slugging does not determine the largest dia. of bore. If there are loose spots in there..and then it tightens up again, the smaller portion will size the slug smaller..when you are slugging the bore, pay particular attention as to how the slug feels going thru.
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