SLugging the barrel

[browningautorifle]

So.. after all that overkill, you only need one ball, right? Not bags, not #4,#3,#2...I know how many sizes of buck there are. He doesn't need them all.

[Peter Laidler]

The trouble (?) with this process is that because you eventually have to remove the slug, you will only ever have the smallest diameter of the barrel marked on the slug to measure.

[vintage hunter]

browningautorifle, your comment was'nt very nice or necessary. I was just trying to be helpful and I did'nt write it for your benefit anyway.

[Tertle]

Sorry guys for my ignorance here, but when ive wanted to check bore diameter for my cast projectiles ive simply made a cast from sulphur.

Its great because you can recycle it! it also allow yoy to really see whats going on. there are a couple of tricks, like ensure the barel is oiled first and be careful not to drop it!.

[Old Lancer]

Forgive me if you think I'm being obtuse but at the risk of stating the bleedin' obvious, why not just make up some reloads using .310 and .311 and just see which one shoots and groups the best, I'm assuming of course you want to actually use the rifle and need to find out which size projectile to use, load workups are much more fun than messing around with buckshot and drifts, JMTPW.

[Peter Laidler]

Here, here Old Lancer........, couldn't agree more. As I say, so long as the slug has to be taken out of the barrel, then you'll only ever get the smallest diameter that it passes on its way through the bore

[browningautorifle]

I wouldn't bother slugging either. I'd just load and shoot.

[newcastle]

never reloaded yet so before I buy the bullets in bulk i'd like to get a decent idea if I have any rifles which need larger Diameter bullets or if I can get one size fits all. thank you all for your assistance.

[Parashooter]

Unless you're shooting cast bullets, there's relatively little to be gained by learning your .303's internal dimensions. Well-constructed jacketed bullets often shoot well in barrels with groove diameters significantly larger than the bullet, the jacket being stiff enough to align bullet with bore axis despite some clearance in the grooves. When bore diameter is so large that the bullet is engraved only lightly by the lands, even stiff-jacketed bullets may yaw in the barrel and fly erratically - but this is a fairly uncommon situation.

Lead-core copper-jacketed bullets up to about 1% (.003" in a .303) larger than groove diameter can also function and group well, although caution is required to ensure adequate neck clearance in the chamber and to work up loads carefully to avoid unexpected high pressure from added resistance as bullet enters barrel.

With cast lead-alloy bullets, too soft to resist off-axis deformation when not carefully fitted to throat and barrel, knowing the relevant dimensions is critical to selecting moulds and sizing dies. Choosing the wrong mould and/or sizer can be a costly error that is avoidable by careful measurement before purchase. Ideally, a cast bullet will provide full land contact through most of its length as well as groove contact on its driving bands and minimal clearance in the throat.

[ireload2]

Slugging a barrel does not have to be a one shot deal.
A slug pushed all the way through can find the tightest spot.
You can also push a slug through to find the loosest spot, then push another slug in from the other direction if needed to slug the loosest place.
So how about the hypothetical loose spot between two tighter areas? That may be a hint you need to lap the tight spots a little just like custom barrel manufacturers do to make the bore more consistent.
I find it interesting that shooters who never reload comment on the slugging process.