Bore slugging tutorial

[Armistice]

I've seen this come up enough over the last few weeks that I fig'd people would like to see how to do it. This process can work for any rifle

http://7.62x54r.net/MosinID/MosinSlug.htm

[GOEX FFF]

I remember using Tom's bore slugging tut many from years ago.
It's a great and simple "How-To". Where it's mentioned "It is best to "flatten" them with the mallet to slightly increase the diameter before using them".
I found this true as well using egg sinkers since they're tapered at both ends where the riding surface is therefore small. The first time I tried it, I forgot to flatten them a bit and the sinker barely had any land/groove impressions to get an accurate measurement.

Another method is using soft lead muzzle-loading round balls that are close enough to your bore diameter/caliber to start.

[Capybara]

I need to get off of my rear and do this this month. So many guns that I have to slug though. Besides Mosins, which other C&R rifles would it be worthwhile doing this to? M48A? K31? SKS? I thought I read somewhere that this is mainly a Mosin thing to do, that the bore diameters on most other milsurps are much more standardized from a reloading POV? What about pistols too?

[Vlad 11]

00 buckshot will work as slugs in .30 cal guns. A shell will give you 9 pellets

Any type of gun can have some amount of variation.

[NOTABIKER]

so is the land dia what is important ?. measuring the high point of the slug is the grove not the barrel Land. the land is what the bullet sees ,not the grove. If i am wrong please correct me.

[MapleSyrupSmuggler]

I've seen this come up enough over the last few weeks that I fig'd people would like to see how to do it. This process can work for any rifle

http://7.62x54r.net/MosinID/MosinSlug.htm

Just did that tonight on my M44 and found out I have a .317 bore as opposed to .313.

Another reason to kick myself for not getting a Finn.

[NOTABIKER]

.317 is that the grove or the land ?

[MapleSyrupSmuggler]

.317 is that the grove or the land ?

It is the groove.

[GOEX FFF]

^^ Yep the groove.

When you slug the bore, the impression of the bore is mirrored where lands will be low and the groove will be high. You want to measure high groove point to opposite high groove point.

[ArmedCMT]

00 buckshot will work as slugs in .30 cal guns. A shell will give you 9 pellets

Any type of gun can have some amount of variation.

Good to know, maybe I'll get to slugging my SKS tomorrow.

[Discogodfather]

This is a good tutorial too:

[Flyin Brian]

so is the land dia what is important ?. measuring the high point of the slug is the grove not the barrel Land. the land is what the bullet sees ,not the grove. If i am wrong please correct me.

The groove diameter is what really matters in regard to bullet selection. I generally use bullets equal to the groove size or .001 larger. I don't generally care about the lands measurement, other than measuring wear. When you see people selling a rifle and they show a photo of a cartridge with the bullet stuck in the muzzle, that is an indication of the size/condition of the lands at the muzzle, but doesn't really help with bullet selection.

[NOTABIKER]

grove

Very good info but please explain how the grove Dia is important. the bullet moves down the bore on the lands. i would think if the land is worn that would affect accuracy. on the other hand the grove has no contact with the bullet [or does it ]. i know very little about the function of lands and groves. As the bullet is squeezed moving down the bore is the outer skin of the bullet making contact with the grove Dia ?. a little more info would clear this subject in my little mind THANKS.

[Flyin Brian]

Very good info but please explain how the grove Dia is important. the bullet moves down the bore on the lands. i would think if the land is worn that would affect accuracy. on the other hand the grove has no contact with the bullet [or does it ]. i know very little about the function of lands and groves. As the bullet is squeezed moving down the bore is the outer skin of the bullet making contact with the grove Dia ?. a little more info would clear this subject in my little mind THANKS.

The bullet is normally the same or larger than the groove diameter by .001" (or a little more for cast bullets). On a .30 cal rifle, the barrel was once a tube with a .300 hole drilled in it, then the grooves were cut, so the lands are the original interior of the tube. That makes the lands in this case .004" taller than the grooves.

When the bullet is forced into the barrel, it is being squeezed down quite a bit, as the overall diameter of the jacket is larger than the grooves, and the '004" tall lands on 4 sides (on a 4 groove barrel) are really crushing it down.

If you think of those "bullet test" photos people do, with a bullet sitting on the muzzle, the only part that actually makes it in the barrel is the nose, so it takes a lot of force to run the bullet down the bore.

It's kind of funny to think of an 03-A3 with a 2 groove barrel, as they only have 2 small grooves cut to .308 and the rest of the tube is .3 so the amount the bullet is being crushed would seem to be enough to cause a problem, but mine all shoot fine

[NOTABIKER]

very good explanation now i get it,