Slugged barrel reading .456 vs Montana .459 bullet

[roscoe]

I plan on casting for my Sharps .45-70 rifle in the near future, but right now I will use some Montana bullets that measure .459. When I slugged the barrel, I get a reading of .456 on the groove diameter and .449 for the bore. I checked the Montana bullets and they are .459. Is it best to size the bullets to .456 before use?

[marlinman93]

I use bullets that are .001" over what the bore slugs to. Never use bore size myself, as I get leading if I do. But I shoot smokeless, and those shooting BP say they get enough bump to use bore sized bullets. .003" over is too much for me. I might try .002", but don't like that far oversized. I'd get a sizing die for my lubrisizer, and size them down, or find the correct .457" bullets somewhere.

[leadman]

The boolit will go down the bore but first you want to make sure there is enough clearance in the throat area of the chamber to have the case neck release the boolit properly. Too tight and the pressure will increase and might cause damage to the gun and you. If you have a case that was fired in the gun with a full load you can check the inside diameter of the neck to see what dimension it is. If no case a chamber cast or pound cast will also give you this info.
Make sure that the slug you drove thru the barrel was actually bottomed out in the grooves. If it the groove to groove is still .456" you might call Montana and see if they can size the boolits down for you, or post a request here and someone will probably help you out. I do not like to go over .002" over bore diameter (groove to groove) myself.

[montana_charlie]

If you have a case that was fired in that chamber, slip one of those bullets in the mouth and chamber it.
If the chamber accepts a .459" bullet, those will fire with no safety concerns.

If the bullet slips in easily (or tends to fall out) you would probably be smart to order a 'fatter bullet size' whenever you go looking for a mould of your own.

Which end of the barrel did you get that .456" reading from?

[Ballistics in Scotland]

If you have a case that was fired in that chamber, slip one of those bullets in the mouth and chamber it.
If the chamber accepts a .459" bullet, those will fire with no safety concerns.

If the bullet slips in easily (or tends to fall out) you would probably be smart to order a 'fatter bullet size' whenever you go looking for a mould of your own.

Which end of the barrel did you get that .456" reading from?

The last is a good point. If you have doubts about a barrel, you should always push slugs all the way through, one in each direction. But the one which goes from the breech and exits the muzzle is the important one.

As has been said, .001in. over bore diameter is a good size, and we are talking only .002in. over that. I don't think it will have any real bearing on pressure (unless someone had a mental aberration about casting in pure linotype, maybe), or on leading. It is irregular finning at the base that would worry me most, and not even that if the bullets were gas-checked.

[roscoe]

If you have a case that was fired in that chamber, slip one of those bullets in the mouth and chamber it.
If the chamber accepts a .459" bullet, those will fire with no safety concerns.

If the bullet slips in easily (or tends to fall out) you would probably be smart to order a 'fatter bullet size' whenever you go looking for a mould of your own.

Which end of the barrel did you get that .456" reading from?

Muzzle end

[montana_charlie]

When you chamber a bullet (in a loaded round) you place it in the breech end of the barrel.
That is where it needs to 'fit the bore' before anything else happens.

Put a slug in the breech end and a rod in from the muzzle to be an 'anvil'.
From the breech end, expand the slug against the anvil, then push it out through the chamber.

THAT is the set of barrel dimensions the bullet needs to fit.

[roscoe]

When you chamber a bullet (in a loaded round) you place it in the breech end of the barrel.
That is where it needs to 'fit the bore' before anything else happens.

Put a slug in the breech end and a rod in from the muzzle to be an 'anvil'.
From the breech end, expand the slug against the anvil, then push it out through the chamber.

THAT is the set of barrel dimensions the bullet needs to fit.

What should I use on each end to do this?

[montana_charlie]

7/16" rod should work well in a .45 caliber barrel.
You could put a short length (2.75") in a 45/70 case.
Stuff a slug up into the chamber, then push the cased rod in behind it and close the breechblock.
From the muzzle end, use a long piece of rod and a mallet to thump on the slug enough to expand it well.
A wrap of Scotch tape every eight or ten inches should protect the bore from the steel.

Drop the breechblock to push the cased rod out, and the slug will follow it.

[Tatume]

To which I'll add, soft blows with a heavy hammer are more effective and safer than sharp blows with a light hammer.

Instead of using a short piece of rod in an empty case, you could fill a case with molten lead. After it cools it works well.

[marlinman93]

I buy muzzleloader round balls for slugging barrels. They are pure lead, and the softest you can find, so they move through the barrel easily. I would never use steel rod in the bore of my rifles, as it can damage your rifling if it gets off to one side. I use my Dewey cleaning rods with a brass jag tip to drive the soft ball through the bore.

I'm puzzled by the comment about "clearance in the throat area"? It's a single shot rifle, and I can't imagine how you can chamber a cartridge with thumb pressure if it was too large? I've occasionally had old singles with very large bores, and seating bullets in the cases caused the case neck to bulge a little. When I tried to chamber them they wouldn't go, so had to ream the case necks to handle the proper diameter large bullet.

[Ballistics in Scotland]

To which I'll add, soft blows with a heavy hammer are more effective and safer than sharp blows with a light hammer.

Instead of using a short piece of rod in an empty case, you could fill a case with molten lead. After it cools it works well.

The case filled with lead should work fine, but you need to discard it afterwards. That muchy heat is enough to impair the work-hardening of the case-head. Filling it with Cerrosafe would be OK though, and it would be easy to remelt and tip out of an internally greased case.

[roscoe]

7/16" rod should work well in a .45 caliber barrel.
You could put a short length (2.75") in a 45/70 case.
Stuff a slug up into the chamber, then push the cased rod in behind it and close the breechblock.
From the muzzle end, use a long piece of rod and a mallet to thump on the slug enough to expand it well.
A wrap of Scotch tape every eight or ten inches should protect the bore from the steel.

Drop the breechblock to push the cased rod out, and the slug will follow it.


Originally Posted by Tatume

To which I'll add, soft blows with a heavy hammer are more effective and safer than sharp blows with a light hammer.

Instead of using a short piece of rod in an empty case, you could fill a case with molten lead. After it cools it works well.

1. I used a .452 cal bullet, 400 grain almost pure lead that I use in my air rifle and dropped in the chamber.

2. I then placed in a case filled with lead. I was able to gently push the bullet up and closed the breech without any issues.

3. I used a .375 brass rod with tightly wound electrical tape and inserted it in the end of the muzzle.

4. Then using a hammer, I gave it several light blows to bump up the bullet. I could feel the nose of the bullet (spitzer style) recessing. When I could not feel it going any further down I stopped.

5. The case popped right out. I had to tap on the rod a little more until it the bullet dropped.

6. Now my readings are: Groove: 459 Bore: .456

[Tatume]

The case filled with lead should work fine, but you need to discard it afterwards. That muchy heat is enough to impair the work-hardening of the case-head. Filling it with Cerrosafe would be OK though, and it would be easy to remelt and tip out of an internally greased case.

I just use discards with mouth splits.

[Red River Rick]

6. Now my readings are: Groove: 459 Bore: .456

Something doesn't sound right. If this is the case, that's pretty shallow rifling.

RRR

[marlinman93]

A .459" groove, and .456" lands, would indicate the groove depth is only .0015" deep. That's either worn out, or crazy shallow.

[roscoe]

I took my rifle to a machinist friend of mine and he checked the bore with gage pins. He then took an ingot of lead I brought along and turned it down to .05 and put a tapered nose on it. I cut it down to .75 long. I drove this through the barrel and took a reading.

Bore: .449
Grove: .456

So now I'm back to my original question.

I checked the Montana bullets and they are .459. Is it best to size the bullets to .456 before use?

[EDG]

If the Montana bullets can be scratched with a thumb nail make sure they are well lubed and shoot them as is.

I took my rifle to a machinist friend of mine and he checked the bore with gage pins. He then took an ingot of lead I brought along and turned it down to .05 and put a tapered nose on it. I cut it down to .75 long. I drove this through the barrel and took a reading.

Bore: .449
Grove: .456

So now I'm back to my original question.

I checked the Montana bullets and they are .459. Is it best to size the bullets to .456 before use?