I'm a little confused on barrel slugging and picking the right boolit.

[rmcelwee]

First topic - So I slugged my Mosin PU Sniper last night. I used a 1/4 oz lead sinker and wooden dowels. I started at the muzzle and worked my way down. I took my calipers and tried to measure the largest part of the boolit. Most measurements were .311 but there were a few places that I got up to .313". I don't understand what I am looking at. I slugged it again and got similar results. I was careful not to drop the boolits when they came out of the rifle. I'm sure I could have disfigured them somehow but I don't really think that was the issue. Is the larger portion some kind of deformity that happens when you pound the slug through the barrel? Again, I was pretty careful when the bullet exited the barrel.

Second topic - Assuming that I do have a .311 bore, what mould do I want to get? I have been looking at the Lee C312-185-1R. I am new to casting and have only done 45 ACP so far. When I did them I PC'd the boolits and then sized them down. I'm guessing that if the Lee will do .312" then I will PC them and size them down to .311". I'm thinking that the full length sizing/priming die for 7.62x54r will make the case necks so that the .311 sized boolit will fit but I might have to get the Lee Universal Flaring die to open it up a bit. Any need for a gas check?

Any help you guys can give me would be very much appreciated!

[Wayne Smith]

First, get rid of the wood dowels for slugging! There is a stickie somewhere on the site about getting a stuck dowel out of a bore. It is not fun - they break cross grain and jam. Get yourself a brass rod or a steel rod and wrap it in duct tape to do this in the future.

Secondly, where and how long are the larger sections??

[largom]

I would use a micrometer instead of calipers for measuring the slugs. Second the "Do not use" of wooden dowels.

Larry

[country gent]

Some barrels have "choke" in them either maachined lapped or thru firing. Ideally the bore gets smaller towards the muzzle. Odd grooves and lands can make measuring tricky at times. If calipers are all you fine bit michrometers give a mich more accurate reading much esier. I would run a slog in a short distance from chamber and back out one to middle of barrel and one a few inches in from muzzle and back out. This gives bore groove dimensions at 3 places. One slug thru will show the tightest spot only. Measure and go .001 over largest spot in bore. Some do a poind cast to get throat dia also and size to that. Lead is a dead metal little to no spring back.

[runfiverun]

those places you got 313 indicate you probably didn't get the slug up to diameter enough to fully measure the inside of the barrel.
I don't slug barrels so I got nothing other than that.

[mdi]

Normally, lead bullets are sized .002" (as a start) over the groove diameter of the barrel. All slugging is is forming/swaging a soft lead slug through the barrel to determine the ID dimensions. You'll need a soft slug(sinker, soft cast bullet, etc.) larger than the largest ID of the barrel (rifling grooves). I too suggest using a micrometer rather than a caliper as the micrometer anvil and spindle have larger surface area to measure with than the thin blades of a caliper.

When I PC my bullets I size to a couple thousandths over groove diameter, coat/cook, and size again. I use the same sizing as if I were not coating...

[Char-Gar]

Just a couple of suggestions that might be of help to you.

1. Using calipers for such a task is an exercise in frustration.
2. Use a micrometer and rotate the slug between the jaws until you find the high spot and that will be your measurement.
3. Don't waste your time slugging barrels. Yes, yes I know everybody is telling you to "slug the bore", but that is a bunch of hooey.
4. The number you want is the diameter of the throat which will be larger than any barrel diameter numbers you come up with.
5. Don't waste you time trying to do a pound slug or chamber case of your throat ether.

Now here is the biggie.....

6. Get a fat 30 caliber mold or one for the 303 Brit, and don't size your bullets smaller than they come from the mold. I am talking shoot .313 or .314 bullets here!

These Roosky Mosin rifles that have been coming in the past few years have been shot, shot and shot some more. They then went back to an armory where they were refinished and put in storage. The net result is they have large worn throats and most are worn around the muzzle end from Russian peasant soldiers using steel rods to clean them.

They are historic, cheap and fun rifles to own and shoot, but don't make work out of this. Just a fat gas cast bullets at around 1.5 to 1.7K fps and be happy. Or, shoot a plain base fat bullet out of soft alloy at 1,100 fps and still be happy.

Addendum: I just want back and re-read your post and you want to powder coat your bullets. Therefore disregard all of the above and you are on your own. I can offer no help and assistance with such an effort.

[Der Gebirgsjager]

This whole thing is a mystery to me! When I run a slug through a bore the bore squeezes it down to the smallest measurement, that's how it comes out, and that's what it measures. They don't swell up to larger sizes. So I'm hazarding a guess that something in your slugging technique is amiss. For what should be a .311 bore I would use a .32 cal. cast lead bullet. I'd start at the breech and pound it through to the muzzle. I use a steel barracks cleaning rod that the handle broke off from years ago. This is a solid rod--no joints. I've got a .50 cal. rod for larger bores. When I can't find a pre-cast bullet of the right size I've got a spool of very soft lead intended for making fishing sinkers. It's about the diameter of a yellow wood pencil. I cut a piece off and put one end on my bench vise's anvil and start tapping the other end with a small hammer. As the length decreases the diameter increases until I have the size slug needed. Based on your findings so far I'd say you'll need to be looking at a .314 diameter boolit for your rifle, but I'd do it over again. Depending on the shape and size of the contact points of your caliper or micrometer, sometimes a caliper is preferable. Remember that when examining your slug you're looking at a reverse picture, so the depressions in the slug are the lands and the ridges are the grooves. Some micrometers will span the gap, whereas a caliper will sit across the ridges or in the grooves. Modern dial and digital calipers are very accurate.

[Animal]

I had pretty good luck using a long slug instead of a round ball. For example, I took a fired .38spl case (unsized with primer remains still in the case), cleaned the gunk out, filled the case with chipped up pieces of soft lead, melted the lead while it was in the case, then added more lead chips to fill the case to the mouth. I drove the cooled lead slug out of the case with a kinetic hammer and proceeded to slug the barrel. The end result gave me a long slug with the lands and grooves engraved perfectly. The long slug made it easier to get a good solid measurement. The trick is to use a fired case that is a caliber larger than the barrel you are slugging. The result was much more repeatable than what I did with a round ball. I'm sure other methods work just fine or better, but this seems to be my preferred method for the moment.

[Pb2au]

My 2 centavos,,,,
Ok, imagine if we took the barrel of your rifle and took a hacksaw and sawed a section out of it. If we looked at that sawn section from one end, it would look something like this:
134448

Now, imagine Mr. Lead slug you drove through it. The highest/widest points you measure on the slug is what corresponds to the green line. We are measuring the distance between the two grooves of the rifling. In local parlance on this forum, it is referred as the "Groove diameter" This is the largest diameter of the rifle.
The distance between the two red arrows is the distance between the rifling themselves. This referred to here typically as the bore diameter.
Common practice that is suggested here is that when you drive the slug through the bore, and measure for the groove diameter, that number, say .311" is your reference to begin with in terms of choosing a boolit size. Most times it is suggest that we add say 0.001" to that number for our desired boolit size.
In short, the idea is to let the boolit go into interference for 0.001" to promote a nice gas tight fit and so on.
Now, what R5R and others mentioned is that they do not slug bores. They follow the practice of finding a boolit/brass combination to fill the throat of the rifle completely. This ensures that Mr. Boolit is as centered in the bore as possible, thus promoting the greatest chance for it to launch, enter and engrave the rifling with the greatest chance of doing so, giving the best accuracy they can facilitate. (Run, I know I am paraphrasing like crazy here, just trying to keep it simple. Please fill in the numerous gaps in my explanation!!!)
So, the question is, which "right" or "better" or "correct"?
My answer is neither is wrong.
So, as Char suggested, pick that boolit, keep the loads simple and just jump in. Take good notes of what you do, and learn from the results.
I hope this helps

[Outpost75]

To determine the correct bullet diameter for a rifle, the groove diameter of the barrel is NOT the determinant.

INSTEAD you want to measure the throat, or the unrifled portion of the barrel forcing cone or "ball seat" ahead of the case mouth, before the rifling starts. The best way to do this is from a chamber cast or upset throat slug.

Most accurate for measurement purposes and easiest is to upset a throat slug, or as some people call it a "pound cast."

Start with a sized case with DEAD primer in its pocket.

Heat up your lead pot, then fill the sized case with DEAD primer plugging the flash hole, and generously overflowing the case.

After the lead cools, clean all spilled lead off the case exterior, then file the exposed lead FLUSH to the case mouth.

Take a piece of PURE lead buckshot or short chunk of pure lead wire and drop it into the EMPTY chamber, letting it fall into the throat of its own weight. (With very long throats you can use a longer piece of wire or a SOFT bullet with long bore-riding nose and not a long grooved section).

Insert your lead-filled dummy case and GENTLY tap it into the chamber using a piece of brass rod until you can close the breech. You are using the lead filled dummy case to force the lead slug into the ORIGIN of rifling. In short throated barrels it helps to drive the slug into the origin of rifling, far enough to chamber the lead dummy behind it, then close the bolt and upset the slug against the lead dummy using a Brownell Squibb Rod threaded onto the end of your cleaning rod. You don't need to use a hammer, just many light taps of the squibb rod against the slug until you get a clear "ringing" sound. It need go no farther!

What you want to measure is the diameter of the UNRIFLED portion of the chamber forward of the case neck BEFORE the rifling starts! Extract the dummy and GENTLY tap the lead slug out and measure it.

THAT is the diameter you want to size your bullets to!

Using Cerrosafe, etc. is more trouble and you then need to compensate for shrinkage, etc.

The upset pure, dead-lead slug is exact and straight forward!
If you forget EVERYTHING you ever read about slugging barrels and simply cast chambers from now on, and get bullets to FIT THE THROAT you will be far happier in the long run.

The limiting factor in bullet diameter is neck clearance.

You MUST measure the neck diameter of the chamber on the cast. Most chambers have enough clearance ahead of a fired case mouth that a properly upset throat slug will get you a portion of the case mouth and its transition angle to the throat or ball seat, so that you can measure neck diameter at the mouth and throat diameter of the ball seat.

The loaded cartridge neck diameter must not be larger than 0.0015" SMALLER than the chamber cast at that point, to ensure safe expansion for bullet release.

This is seldom a problem in the Russian M91/30s and Chinese copies chambers are notoriously sloppy!

In a typical Finnish M39 7.62x54 chamber the chamber neck is 0.340". Typical case mouth wall thickness of Norma or Sako commercial brass is 0.013," so .340" minus twice neck thickness (0.026") = .314", minus 0.0015 for safe expansion = .3125" max. bullet for a typical Finn chamber in an M24, M27, M28, M28/30 or M39.

It is not unusual for WW2-era Russian and later Chicom rifles to have throats as large as .316" and groove diameters of .314". If you expect anything resembling normal accuracy you MUST cast your chamber, measure it, and then buy a mold which fits your THROAT, not the groove diameter of the barrel.

As a general rule the largest diameter of cast bullet which chambers and extracts freely, without resistance, will shoot best. For most Finnish rifles this is .311-.312" and for Russian and Chicom rifles .313-.314".

Use .30 cal. gaschecks, pressing them on by hand and then pushing the base of the bullet against a table edge until the gascheck is bottomed against the bullet shank. Only then size the bullet. Otherwise the GC will not be seated squarely on the base of the bullet and any hope for accuracy goes out the window.

The Lee C312-155-2R was designed for the 7.62x39 and also gives good results in most 7.62x54 rifles when cast 12 BHN or harder, sized to THROAT diameter, and loaded with 16 grs. of #2400 for plinking, or 30 grs. of 4895, 4064, RL15 or Varget, if you want a heavier hunting load.

[wmitty]

I checked a Savage 340 .30-30 last nite as described above; groove dia. was .3095" but throat was .312"... I am trying to shoot the NOE 311407 modified plain base in the rifle, it drops at .313" and I'm sizing to .312".

[krallstar]

Use your calipers to measure the inside neck of a fired case from your rifle. This will give you a rough estimate of how big the neck area on your rifle is. Mine measures out to .319. I size them down to .316 with a gc.

[runfiverun]

Pb.
you got it down enough to simplify it.
the simple explanation is quite often enough to let the listener hear what you are saying.

then a technical answer like outpost-75 put up will fill in the gaps enough for the interested to follow through on and figure out how to do it for them self.
i do it slightly different but close-nuff to this method that i can't add anything.

[Landshark9025]

+1

I've not done rifles yet- my M44 is high on my "next" list for casting journeys. However, when I slugged my pistols, this is what I did. I might recommend you go one step further and clean the inside of the case with a wire brush or lemon juice or similar. Mine were kind of hard to see the land and groove impressions due to the dirt they picked up from the case. That said, it does make for a great slug to drive through the barrel.


I had pretty good luck using a long slug instead of a round ball. For example, I took a fired .38spl case (unsized with primer remains still in the case), cleaned the gunk out, filled the case with chipped up pieces of soft lead, melted the lead while it was in the case, then added more lead chips to fill the case to the mouth. I drove the cooled lead slug out of the case with a kinetic hammer and proceeded to slug the barrel. The end result gave me a long slug with the lands and grooves engraved perfectly. The long slug made it easier to get a good solid measurement. The trick is to use a fired case that is a caliber larger than the barrel you are slugging. The result was much more repeatable than what I did with a round ball. I'm sure other methods work just fine or better, but this seems to be my preferred method for the moment.

[MBTcustom]

To determine the correct bullet diameter for a rifle, the groove diameter of the barrel is NOT the determinant.

INSTEAD you want to measure the throat, or the unrifled portion of the barrel forcing cone or "ball seat" ahead of the case mouth, before the rifling starts. The best way to do this is from a chamber cast or upset throat slug.

Most accurate for measurement purposes and easiest is to upset a throat slug, or as some people call it a "pound cast."

Start with a sized case with DEAD primer in its pocket.

Heat up your lead pot, then fill the sized case with DEAD primer plugging the flash hole, and generously overflowing the case.

After the lead cools, clean all spilled lead off the case exterior, then file the exposed lead FLUSH to the case mouth.

Take a piece of PURE lead buckshot or short chunk of pure lead wire and drop it into the EMPTY chamber, letting it fall into the throat of its own weight. (With very long throats you can use a longer piece of wire or a SOFT bullet with long bore-riding nose and not a long grooved section).

Insert your lead-filled dummy case and GENTLY tap it into the chamber using a piece of brass rod until you can close the breech. You are using the lead filled dummy case to force the lead slug into the ORIGIN of rifling. In short throated barrels it helps to drive the slug into the origin of rifling, far enough to chamber the lead dummy behind it, then close the bolt and upset the slug against the lead dummy using a Brownell Squibb Rod threaded onto the end of your cleaning rod. You don't need to use a hammer, just many light taps of the squibb rod against the slug until you get a clear "ringing" sound. It need go no farther!

What you want to measure is the diameter of the UNRIFLED portion of the chamber forward of the case neck BEFORE the rifling starts! Extract the dummy and GENTLY tap the lead slug out and measure it.

THAT is the diameter you want to size your bullets to!

Using Cerrosafe, etc. is more trouble and you then need to compensate for shrinkage, etc.

The upset pure, dead-lead slug is exact and straight forward!
If you forget EVERYTHING you ever read about slugging barrels and simply cast chambers from now on, and get bullets to FIT THE THROAT you will be far happier in the long run.

The limiting factor in bullet diameter is neck clearance.

You MUST measure the neck diameter of the chamber on the cast. Most chambers have enough clearance ahead of a fired case mouth that a properly upset throat slug will get you a portion of the case mouth and its transition angle to the throat or ball seat, so that you can measure neck diameter at the mouth and throat diameter of the ball seat.

The loaded cartridge neck diameter must not be larger than 0.0015" SMALLER than the chamber cast at that point, to ensure safe expansion for bullet release.

This is seldom a problem in the Russian M91/30s and Chinese copies chambers are notoriously sloppy!

In a typical Finnish M39 7.62x54 chamber the chamber neck is 0.340". Typical case mouth wall thickness of Norma or Sako commercial brass is 0.013," so .340" minus twice neck thickness (0.026") = .314", minus 0.0015 for safe expansion = .3125" max. bullet for a typical Finn chamber in an M24, M27, M28, M28/30 or M39.

It is not unusual for WW2-era Russian and later Chicom rifles to have throats as large as .316" and groove diameters of .314". If you expect anything resembling normal accuracy you MUST cast your chamber, measure it, and then buy a mold which fits your THROAT, not the groove diameter of the barrel.

As a general rule the largest diameter of cast bullet which chambers and extracts freely, without resistance, will shoot best. For most Finnish rifles this is .311-.312" and for Russian and Chicom rifles .313-.314".

Use .30 cal. gaschecks, pressing them on by hand and then pushing the base of the bullet against a table edge until the gascheck is bottomed against the bullet shank. Only then size the bullet. Otherwise the GC will not be seated squarely on the base of the bullet and any hope for accuracy goes out the window.

The Lee C312-155-2R was designed for the 7.62x39 and also gives good results in most 7.62x54 rifles when cast 12 BHN or harder, sized to THROAT diameter, and loaded with 16 grs. of #2400 for plinking, or 30 grs. of 4895, 4064, RL15 or Varget, if you want a heavier hunting load.

Best answer.
I don't personally do a pound cast in this way, and have written a sticky on the subject called "FYI this is how I do a pound cast", but everything outpost75 said is the gods honest truth, and the places he says to measure are exactly right.
This is good advice to anyone wanting to shoot cast in a rifle.

[dubber123]

I'm not sure if I missed it, but it is worth noting not all bores are round. Oval is pretty common, even on some expensive guns. This was part of the OP's question.

[Ken in Iowa]

As for mould selection, the Lee C312-185-1R is not a bad choice for a cheap starter. The first cast boolits I used in a Mosin were from this mould.

Another member here here by the handle of Texassako, recommended the 311331. It is better suited to the shorter neck of the 7.62x54r. I picked up an NOE 311331 mould but have not fired any as yet. Mine drops isotope lead at .313

For neck expansion, look at the Lyman 31R 'M' die, or better yet the NOE expander plugs. The 31R is fine for .312 to .314 boolits or .311 or .312 jacketed bullits.

If you are on a budget or don't want to get in too deep yet, shoot without a gas check at lower velocities. Perhaps you can use the alloy and powder that you already have on hand for 45 ACP.

Good luck and have fun!

[fast ronnie]

First, get rid of the wood dowels for slugging! There is a stickie somewhere on the site about getting a stuck dowel out of a bore. It is not fun - they break cross grain and jam. Get yourself a brass rod or a steel rod and wrap it in duct tape to do this in the future.

Secondly, where and how long are the larger sections??

A good way to coat a cleaning or pounding rod is heat-shrink tubing. It is cheap $2 or $3 for a 3' piece, and is thin enough to use a 1/4" rod in a thirty caliber bore. 3/16" plus heat-shrink for 7mm.

[GhostHawk]

I'm with Ken I've had pretty good luck with my Lee .312-185. It did work better yet when I beagled it with 3 small strips of alum tape, then it was dropping .314, gas checks got harder to put on, but once crimped on with a .314 sizer they got rock solid.

Lee sizers seem to be running a touch small, mine are .314 going in and come out .3135 which is about perfect for my .312 Mosin's barrel.

I'm using the same mold at .312 to make boolits for my Yugo SKS, she seems to like them long and set out as long as will clear the mag.

It is an interesting journey, where you end up at who knows.