Anyway to find what diameter bullet to use?

[Robert Palermo]

If you don't want to slug the bore or have somebody else do it then the solution is to get cast bullets either bought or made yourself in different diameters and try them in the gun seeing which ones shoot the best.
Try .311, .312, .313 and see what you get.

[Unclenick]

Fishing sinkers where I am are lead-free. Too hard and springy for slugging. Hornady makes a .32 caliber pure lead ball that is 0.315". That will work fine.

Don't use a caliper to measure the bore directly with its inside jaws, as these typically measure small holes a couple of thousandths undersize.


You can use a caliper to compare one item to another, but for absolute readings you need a dial type caliper and a calibration standard and to be skilled at making delicate readings with it and interpolating between the graduations. Or, more easy, you want use an OD thimble micrometer with 0.0001" resolution on a Vernier scale. $14 + shipping here. Harbor Freight has one with mechanical digit counter for about $22, which might be cheaper after shipping costs, if you have an HF store near you. Just remember to clean the anvil and spindle nose and check zero first, to find the offset to add to your reading.

Slugging with the ball, use a 1/4" brass dowel rod. You can get them at Lowe's. Run a lightly oiled patch down the bore and lightly oil the ball. Cut a couple or three inches off the brass dowel and use that to drive the slug in at the muzzle with light taps from a plastic hammer (don't want a glancing blow to mark the gun). Once it has started in, you can push it back out from the other end with the brass dowel. That will give you a muzzle measurement. You can do the same in reverse to get a throat measurement, removing the bolt, and, with the muzzle down, dropping the ball into the chamber and then using the weight of the long dowel as its own hammer to tap the ball into the throat. You can also push a ball slowly through the whole bore with the long part of the dowel. This lets you feel for tight or loose spots that may benefit from firelapping. Do it from both ends and you will feel the difference and be able to tell more.

You will find the tightest spot in the bore somewhere along the line. With luck, the muzzle is tightest, though this matters most for cast bullet shooting. And since the balls are 100 per box, you'll still have 96 left for monitoring firelapping progress or for helping friend measure their ≈.30 cal rifles or for checking others of your own.

[FrankenMauser]

Slugging is simple. There are plenty of You Tube videos out there to show you how.

I use a conical lead plastic worm fishing sinkers exclusively. They are pointed thus easy to start and leave plenty of rifling to mike.

Conical Lead is superior to round balls.

Were I in need of a fishing sinker to slug a bore, I'd have the same problem as Unclenick: Everything here is iron, steel, or zinc.

Like with wheel weights, you can no longer assume, with any certainty, that lead will be available in any given part of the country.

[chiefr]

I agree, many are not made of lead. I have tossed them in my casting pot to see them float on top.
Soft or pure lead is not a problem where I am at. I have plenty.

[44 AMP]

I'm not really to keen on forcing a hunk of metal down my bore.

Which is what happens every time you SHOOT the gun!
sighs....

a lead slug is softer than barrel steel, pushed through the bore without the heat& pressure of powdergasses, it can do no harm.

One advantage to (correctly) slugging the bore is that the process will tell you if the bore has any tight or loose spots. You tell this by the feel of it as it is driven through. The slug will,of course, remain the diameter of the smallest part of the bore it passes through.

The 7,62x54 is nominally a .30 caliber, and generally the spec call for a .311-.312" bullet. BUT, combine production tolerances and who knows what has happened to the rifle in the decades (or in some cases century+) since it was made, and you will often find a significant variance from the spec.

[guncheese]

i use .36 or .45 cal round balls to slug all my stuff
they are very soft
i just did my SKS a couple weeks ago
put the ball on the muzzle, and wacked it a few times with a safety mallet
drives the slug into the bore and shaves off the unneeded lead then pound it thru with a dowel
pistols, rifles,revolvers i do them all the same way with a round ball
if doing 9mm or .357, just wack the 36cal ball with a mallet on a plate to fatten it out a bit
to make sure your filling the grooves

[FrankenMauser]

Guncheese,
If you lube the bore first, there is no need to "pound it thru". You can push the slug through by hand, once it's started.

[guncheese]

yes ive found that to be true
but whats the fun in that?!!

[Unclenick]

The reason for pushing through - slowly - is to feel for tight and loose spots to determine if you need some lapping or, in the case of a new barrel blank, which end will make a better muzzle (the narrower end). You'll even find they don't feel the same pushed in opposite directions. Some imperfections can be identified pushing in one direction but not the other. A hammer won't let you feel any of that.

Also, you should be able to push a pure lead through even without oil. It's just not as smooth. If you have a slug that won't budge without a hammer being applied, then it's not pure lead, but some harder and more springy alloy tightening up against the bore. The elasticity of such alloys makes precise measurements and locating of imperfections impossible.