Cast bullet size

[Snagman]

Why is it that I reload with a .308 size jacketed bullet and yet the cast boolits are .309 and the sizer die is also .309? Why are cast boolits .001" larger than the bore of the firearm?

[Boolseye]

Copper jacketed bullets can catch the rifling with less width and still do their thing. Cast bullets need a bit more size in relation to the bore to work properly.
They will skid on the rifling at high velocity otherwise, and cause leading in the barrel.


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[Rcmaveric]

That's a large debate. Size to what will work. Size your bullets to what your gun likes. Some size to bore diameter and it works for them, but not me. Some size .001-.002 over and it works great and others size to throat. It all has to do with gas cutting and obturation. A jacket bullet is protected, so gasses can cut and not really mess up your accuracy by deforming the bullet before it has a chance to obturate and seal the bore. Sizing .001 to .002 ensures quicker obturation when the bullets passes into to the riffling. Down side to .001 to .002 is the thought that gasses can still cut around the bullet when it passes into the throat, through the leade and into the riffling. The thought behind sizing to throat is that the throat supports the bullet during ignition and helps keep the throat sealed to prevent gas cutting thereby increasing accuracy. So, try out all the methods, research them and see what works for you. I personally prefer to size to throat.

[GhostHawk]

rcmaveric is giving you the straight dope.

In the end let your rifle tell you what it needs.

But for cast 1-3 thousandths bigger is a good place to start.

[HangFireW8]

Sizing to groove diameter has worked well for me, but even 1/10,000th under and one can get gas blowby and leading from flame cutting. So the rule of the thumb has been .001" over just to make sure. Some guns have further requirements, especially those with large/long throats. Revolvers are in a category all to themselves when it comes to sizing and alloy requirements.

Be wary of anyone here who starts out with a post with "have to". Undersized boolits can work quite well, if soft and/or driven hard enough to get them to "slug up" or expand to the point they obturate (fully block the bore). Also a copper gas check can cure a multitude of ills. I personally shot a bunch of .309" sized cast in my ".308 bore" FN 30/06... zero leading, good accuracy... until I slugged the bore and found out it was really a .310" bore. Since then I've switched to .310" (most of my molds just won't drop at .311") and continue to make advancements in accuracy.

But having said that, I don't recommend starting off with undersize boolits, if it can be avoided at all.

[white eagle]

some time it works out best to size larger than bore size
not always though like others have said a reference not a rule
only your rifle,gun knows for sure

[Dusty Bannister]

Don't you guys mean to size larger than groove diameter?

[JonB_in_Glencoe]

Why is it that I reload with a .308 size jacketed bullet and yet the cast boolits are .309 and the sizer die is also .309? Why are cast boolits .001" larger than the bore of the firearm?

The "why" is that ideally, you want the cast boolit to fill the grooves. If your boolit is .001 over barrel groove diameter, that is more than likely gonna happen.

[Catpop]

Success of shooting cast boolits is fit of boolit to actual groove diameter plus .0005 (or more.) This has nothing to do with what caliber the gun is marked, but rather what the groove actually measures.
Once that is established other factors come onto play.
“Fit is King”

[runfiverun]

the initial 'fit' is in the throat not the barrel.
the most and the hottest gas is concentrated right there.
stop the gas cutting before it starts and you won't have to try and figure out why you have leading and/or poor accuracy.

[Boolseye]

Don't you guys mean to size larger than groove diameter?

Yes. At least .001” larger than groove diameter. I just slug my barrels and go from there. Works for me. Never done the throat thing.


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[HangFireW8]

the initial 'fit' is in the throat not the barrel.
the most and the hottest gas is concentrated right there.
stop the gas cutting before it starts and you won't have to try and figure out why you have leading and/or poor accuracy.

This again.

The gas is not concentrated there in all cases.

Sizing to groove instead of throat often works very well.

Sizing to throat is often not necessary. Of sometimes, even possible.

[Buckshot]

.............Snagman, as being new to the board, and possibly cast lead boolits some clarification might come in handy, maybe not, but here goes: The Bore, this is the ID from the top of one land to the top of the opposing land. In a 30 cal rifle we'll figure the BORE is .300". However, the term 'Bore' can also take in the entire interior surface of the barrel encompassing the lands AND the grooves. Grooves are descriptive of what they are. They are the grooves cut into the BORE to create rifling. If this is not new then please forgive me for assuming :-)

http://www.fototime.com/CD3C27CAC75B24B/standard.jpg

Not having a sectioned barrel, I'll just use this drawing I did for showing the chambering on a M1879 Argentine contract Remington Rolling Block rifle, vs the more common chambering we're used to. In the lower drawing is the type we're most accustomed to. The throat is the unrifled portion of the barrel directly in front of the chamber. Obviously the drawing is exaggerated. By fitting the cast lead slug to 'Just' fit the throat can help marginalize the afore mentioned 'Gas Cutting' of the lead slug which will majorly have a detrimental affect on the lead slug.

The most perfect example of gas cutting I ever saw was a recovered 58 cal Minie' boolit. I wished I'd saved it. Cast of pure lead probably in a cold mould. It looked like a tiny acetylene torch had gotten to it. There was a cut place through the bottom band. The gas then followed a grease groove about half way around the Minie' where it encountered another wrinkled drive band, and passed through into the middle lube groove. Then ditto for the top drive band where the gas found release to the atmosphere. It had the appearance like where a small narrow stream of water had wondered around on a mud flat. It's obvious path was very smooth. It's usually a good idea to size to the throat if possible.

However sometimes the firearm may not allow for sizing to the throat. This usually happens in older rifles, or military surplus rifles. One of the best examples of this I can think of would be the Austro-Hungarian M1895 rifles/carbines chambered to 8x56R.

Another way to defeat gas cutting, is if the cast lead bullet is long enough to engrave in the leade while the base is still in the neck. Upon initial ignition the boolit can seal the barrel, and there is no place for the gas to go, except to remain behind the slug and push :-) If the gas can find a place to escape to the low pressure atmosphere, it WILL go there :-)

..................Buckshot

[HangFireW8]

Thanks for the terminology correction, Buckshot. Yes, technically bore sized boolits would ride the lands. What I am saying is that filling the grooves is often enough. If it is not, then sure, fill the throat.

Also what I am saying is that there is more than one way to get sizing to work. I am getting more than a little tired of some who think there is only one way, or that beginners have to do things there way.

Some older BP cartridges rely on upset to seal. Sizing to throat will result in a cartridge that will not chamber. But good results can be had with proper alloy and start force.

Also hard, long boolits can seal the bore quickly even if sized to groove. Good results can be had without filling the throat with an oversized boolit.

There is no need to force every question into the fill the throat answer.

[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. The way I do this is to heat the 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 first 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 let the weight of the rod drop onto the slug, making 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 lots 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 safe cast bullet diameter is neck clearance. You MUST also 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 absolutely essential for custom target barrels which often have tight-necked chambers which require neck-turned cases.

As a general rule the largest diameter of cast bullet which chambers and extracts freely, without resistance, will shoot best.

For instance in a .308 Winchester target rifle with .339" tight-necked chamber and using case necks turned to 0.012," maximum bullet diameter is determined by"

[neck (.339")-2(neck wall thickness 0.012)] - 0.0015 = 0.3135" for a "fitted neck" in which fired cases do not require sizing, but bullets will be held by case springback only. For necked sized fixed ammo, subtract another 0.0015" or .312" IF the chamber ball seat is that large. In a new barrel chambered for jacketed bullets, probably not. Min. SAAMI throat as on the .308 Winchester pressure test barrel is 0.3105".

Unless you know that your particular throat is cut smaller with a non-standard, custom reamer, try .310", which works in most.
If the barrel has been fired more than 1500 rounds with full power jacketed loads .311" will probably fit better. If you shot a couple seasons season of NRA highpower with it, with lots of rapid fire and barrel heating, then .312" will fit just fine.

John Ardito set all of his CBA benchrest records shooting .312" bullets in his .308 Win. and wildcat .30 cal. rifles.

Bullet fit is seldom a problem in milsurp because military chambers tend to be sloppy!

[stubshaft]

One of the most important things to remember is that no matter what you size the boolit to. You will need a properly sized "M" die to expand the case mouth!

[Outpost75]

One of the most important things to remember is that no matter what you size the boolit to. You will need a properly sized "M" die to expand the case mouth!

Good point. Another thing is that you don't want the expander plug to be more than 0.002" smaller than the bullet, otherwise when a larger cast bullet is jammed into a tight neck, it will "size" a soft bullet and may deform and crumple a soft, thin case neck as in the .32-20, .38-40 or .44-40 cartridges.

The RCBS cast bullet neck expander is available with plugs in 0.001" increments and Buckshot and NOE also make custom plugs.

I always inside deburr cast bullet cases well to break the sharp inside corner of the case mouth, which reduces the tendency to shave lead if the case is perhaps not belled quite enough, which can be common with mixed range brass which people seldom trim to uniform length.

[stubshaft]

Buckshot is not making expander plugs anymore...much to my regret.

[Grmps]

https://i.imgur.com/ufMhCrH.png

[HangFireW8]

John Ardito set all of his CBA benchrest records shooting .312" bullets in his .308 Win. and wildcat .30 cal. rifles.

Hmm I have custom barreled rifles, some of them chambered in .308 caliber. Guess what the throat size is cut to? (The answer is in there).


One of the most important things to remember is that no matter what you size the boolit to. You will need a properly sized "M" die to expand the case mouth!

I've found the sharp step of the "M" expander knocks cases eccentric. But then most here don't ever measure that, so I guess they wouldn't know.

[Outpost75]

I bought a couple pull-off barrels from John Ardito which I set back and rechambered, but before doing so I cast the chambers and blew the castings up on an optical comparator and measured them, neck diameter was .335" cylindrical with chamfer at end of case mouth 15 degrees, Basic, and forcing cone had a major diameter of 0.3124" with no cylindrical ball seat, but a forcing cone angle of 0 degrees, 45 minutes, Basic. "Fitted neck" chamber did not require cases to be resized, springback held the bullet.

John reloaded ONE case sequentially at the range, decapping the fired case, cleaning the primer pocket and priming, charging the case with either 28 grs. of H322 or 24 grs. of RL7 and seating the bumped, nose-pour bullet from mold he cut himself into the unsized case mouth with his fingers, inserting it and closing the bolt. If you extracted a loaded round without firing it was held in the case by the GC and base band only. Bullets were bumped in a swage cut with the same chambering reamer used to cut the barrel, so that bullet was tapered and bumped to fit exactly. Alloy was a blend of linotype and monotype about 24 BHN. His loads in .308x1.625" with 40 degree shoulder chronographed about 2300 fps from a 28" barrel on an Unlimited gun and 2000 fps from a 20" Hunter class gun. His heavy guns were half-minute any time any where on demand... Bullets were 175 grain in Hunter class and 210 grains in Heavy BR. He mixed his own lube from beeswax and STP with a bit of carnuba.

[geargnasher]

A "system" which functions acceptably at 1600 fps is liable to generate some false conclusions about fit and a host of other things, unless the operator also understands the necessary mechanisms of achieving acceptable results at higher velocity and thus has the experience to know the things which are more generally true and what is true only in certain instances.

Many of the techniques and methods for fine consistency and high velocity with cast bullets tend to be similar, and are applicable to lighter loads as well, where the reverse is not necessarily true. Context is important when making general statements.

Sizing to throat entrance diameter or a few tenths smaller, and having some reasonable contour match between the entire leade section of the barrel and the bullet nose (to support and guide the bullet straight as it compresses into the bore) such as in the excellent illustration Grpms posted above are two examples of good, universal cast bullet loading practices. As Buckshot mentioned, achieving either of these fitment goals is not always possible, as anyone who has loaded for a 38-55 will be well aware, but I find those situations to be special cases, requiring special attention and techniques, and more the exception than the norm.

I too find the stepped "M" expander spuds to be deficient. For one thing, the ones made by Lyman are almost never the exact diameter needed. For another, the size difference between the smaller and larger spud journal diameters is always too great. Finally, the transitional step between the diameters is too abrupt to provide a smooth transition for the bullet base as it is seated. The cast bullet neck expanding dies made by RCBS, as Outpost 75 mentioned, are of the proper form and size selection to achieve the best results...objectively, though sometimes, for light loads, plenty of folks have made themselves quite happy using regular production resizing dies and only flaring their case mouths with needle-nose pliers.

Gear

[HangFireW8]

To the OP,

Rest assured all reasonable cast boolit goals can be reached up to 2200 fps with your current .001 over mold and sizer... and has been by a majority of cast shooters for more than half a century.

For some reason the custom barrel, high velocity debate society here has lost sight of this simple fact.

[runfiverun]

or that's what one of us said, and someone else just wanted to argue.

[Snagman]

Thanks to everyone for the information. Some of this I knew already but a lot of good info I didn't kniw. I've loaded about 100 rounds for my 300 blackout with 230 gr boolit and 11.4 gr of AA-1680. I've heard several people claiming it shoots well with that load so I figured it might be a good starting point. Others claim this boolit will keyhole at about 50 yds because the front of the bullet is .300 and the last 1/3 (in the lube grooves) will measure. 309. So the front portion rides the bore, gets a slight wobble, and then keyhole downrange. Guess I'll find out soon enough.

My question is could I take a .312 boolit and resize it to .309 or .310 so the entire length engages the rifling? Some say I'm disrupting the melicular structure of the boolit if I do that.
Any thoughts?

[HangFireW8]

For bore riders, I use a hard alloy, water dropped, and lube the bore riding nose lightly with thinned LLA. Then I load them ( if possible) just touching the lands. That, checking loads carefully for run-out, and a slower powder for a soft start, gives them a better chance of staying aligned.

Any sizing or reforming affects/softens the lead alloy that is reformed. Ideally all are molds would drop perfectly sized boolits for our guns and need no sizing. Reforming or "bumping up" affects overall hardness more as it moves metal around deeper than the skin, as light resizing does.

Heat treatment in an oven can be done after sizing or reforming If needed. I haven't needed it yet, but will keep that in mind in case I do.

[Char-Gar]

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. The way I do this is to heat the 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 first 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 let the weight of the rod drop onto the slug, making 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 lots 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 safe cast bullet diameter is neck clearance. You MUST also 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 absolutely essential for custom target barrels which often have tight-necked chambers which require neck-turned cases.

As a general rule the largest diameter of cast bullet which chambers and extracts freely, without resistance, will shoot best.

For instance in a .308 Winchester target rifle with .339" tight-necked chamber and using case necks turned to 0.012," maximum bullet diameter is determined by"

[neck (.339")-2(neck wall thickness 0.012)] - 0.0015 = 0.3135" for a "fitted neck" in which fired cases do not require sizing, but bullets will be held by case springback only. For necked sized fixed ammo, subtract another 0.0015" or .312" IF the chamber ball seat is that large. In a new barrel chambered for jacketed bullets, probably not. Min. SAAMI throat as on the .308 Winchester pressure test barrel is 0.3105".

Unless you know that your particular throat is cut smaller with a non-standard, custom reamer, try .310", which works in most.
If the barrel has been fired more than 1500 rounds with full power jacketed loads .311" will probably fit better. If you shot a couple seasons season of NRA highpower with it, with lots of rapid fire and barrel heating, then .312" will fit just fine.

John Ardito set all of his CBA benchrest records shooting .312" bullets in his .308 Win. and wildcat .30 cal. rifles.

Bullet fit is seldom a problem in milsurp because military chambers tend to be sloppy!

___________________________________________

Yes, yes and yes again. Outpost is 100% correct. I don't when if ever folks will ever get over thinking land and groove diameter is the key number. The sooner folks come to understand this, the sooner they will be moving toward ultimate cast bullet accuracy.

[Outpost75]

___________________________________________

Yes, yes and yes again. Outpost is 100% correct. I don't when if ever folks will ever get over thinking land and groove diameter is the key number. The sooner folks come to understand this, the sooner they will be moving toward ultimate cast bullet accuracy.

I have repeated this same old song so many times, I might implore that the Mods consider making it a sticky unless they truly believe all the old wives tales, mythology and folklore in the old Lyman manuals too...

[JonB_in_Glencoe]

Ok, I'll make this a sticky.

[Outpost75]

Ok, I'll make this a sticky.

Merci Beaucoups!

[Beerd]

so does a bore riding portion of a bullet bump up to fill the groves when fired?
..

[Char-Gar]

so does a bore riding portion of a bullet bump up to fill the groves when fired?
..

Nope!

[Outpost75]

so does a bore riding portion of a bullet bump up to fill the groves when fired?
..

That depends upon whether you believe in the Easter Bunny and The Moth Man...

If the bullet does not "fit" during initial shot-start, it is impossible for it to upset uniformly and remain balanced and concentric.

Non-fit is a non-starter!

[HangFireW8]

So was JM Browning the Easter Bunny and Winchester the Mothman, or the other way around?

But somehow they made it work.

[Outpost75]

So was JM Browning the Easter Bunny and Winchester the Mothman, or the other way around?

But somehow they made it work.

There is no simple answer, too many variables, good lab problem in finite element analysis, and strength of materials.

[HangFireW8]

It's not rocket science to bump up undersized soft lead. Just about every early Winchester did it. Many here do it in old revolvers.

But for you it's either the Easter Bunny or an unsolvable science problem.

Yet you are happy to tell everyone what they "must" do.

[Outpost75]

It's not rocket science to bump up undersized soft lead. Just about every early Winchester did it. Many here do it in old revolvers.

But for you it's either the Easter Bunny or an unsolvable science problem.

Yet you are happy to tell everyone what they "must" do.

Soft lead, black powder and fast-burning smokeless pistol powders are easy, and yes, bullets will increase in diameter due to axial compression during initial shot-start, but if the bullet is not concentric to the bore axis when launched the upset will be asymmetrical. But not everyone uses soft bullets and fast powders, and the variables of chamber size to cartridge case clearance and alignment of bullet axis to bore axis all throw the simple assumptions out the window.

[vrh]

I cast bullets from both 170 grain Lyman molds and from 170 grain Lee molds for my 30-06 rifle. The lee mold throws a perfect 309 dia. bullet.
The Lyman throws a .311 dia. bullet. I size both in my Lee .309 bullet size. I powder coat them and again resize them. Both shoot really well.

[Ermine]

I have always found if a rifle bullet is worth the trouble casting then put a gas check on it. Size
.001 oversize and go for it. I've been at it for 48 years and have tried all the "witch craft" that's out there and then some.
I started with wheel weights and that's what I use. It is soft enough to,obturate in the bore and easy to swage if you must?
Pistol bullets generally don't require a gas check unless you want to pressure them up for hunting or home defence purposes.

[Black Jaque Janaviac]

Outpost,
I'm not sure I'm understanding everything properly, but not all chambers are the same. I have Rossi '92 lever actions chambered for the straight-case .357. Their "throat" is not like the diagrams posted in this thread. They have something more like a cone. So to size for throat diameter you'd need a .375 boolit or something like that which would not do. Basically it would be a like a big .22 longrifle with boolit and case the same diameter.

[Outpost75]

Outpost,
I'm not sure I'm understanding everything properly, but not all chambers are the same. I have Rossi '92 lever actions chambered for the straight-case .357. Their "throat" is not like the diagrams posted in this thread. They have something more like a cone. So to size for throat diameter you'd need a .375 boolit or something like that which would not do. Basically it would be a like a big .22 longrifle with boolit and case the same diameter.

In "black powder type" rifle chambers, typically in revolver "Cowboy" calibers such as the .38 Special, .44 Magnum, .45 Colt and .45-70, in which there is no "throat" or "ball seat," before the origin of rifling, load a lead bullet of the largest diameter which provides safe case release clearance, producing a loaded cartridge diameter which measures 0.0015"-0.0020" less than a chamber cast at the case mouth. This permits a loaded cartridge to be chambered easily and extracted without firing, doing so without difficulty. Light marking of an exposed front driving band or exposed bullet ogive which does not impede easy chambering or extraction of unfired rounds does no harm.

In my Marlin Microgroove rifles I load .360" in .38/357, .433" in .44 Magnum, .455" in .45 Colt and .460" in .45-70. Your mileage may vary.

[Steven66]

In "black powder type" rifle chambers, typically in revolver "Cowboy" calibers such as the .38 Special, .44 Magnum, .45 Colt and .45-70, in which there is no "throat" or "ball seat," before the origin of rifling, load a lead bullet of the largest diameter which provides safe case release clearance, producing a loaded cartridge diameter which measures 0.0015"-0.0020" less than a chamber cast at the case mouth. This permits a loaded cartridge to be chambered easily and extracted without firing, doing so without difficulty. Light marking of an exposed front driving band or exposed bullet ogive which does not impede easy chambering or extraction of unfired rounds does no harm.

In my Marlin Microgroove rifles I load .360" in .38/357, .433" in .44 Magnum, .455" in .45 Colt and .460" in .45-70. Your mileage may vary.

Thanks for this. I was worried my Ruger 77/357 chamber was wrong. It measures 0.3615" just ahead of the case mouth. I'm planning to get a NOE mold since they claim a diameter of 0.360" for their 38/357 bullet molds using wheel weights. The 360-154-WFN-AN1 seems like it would work well.

[Outpost75]

Here is useful example, Accurate #31-215B as-cast at .316" diameter in Yugo nny 7.62x54R brass, chambered than extracted from a Tikka M39 rifle. Rounds with the unsized .316" bullet chambered without resistance, and upon extraction shot light, but distinct marking at the throat and also on the forepart where it contacts the origin of rifling.

This demonstrates perfect bullet "fit" and yes, these bullets shoot very well indeed.

225946

[a danl]

because if the cast bullet is too small you will get gas cutting and that will completely ruin accuracy . lead is a totally different situation to deal with, hardness,lube, shape, etc all according to velocity. and of course leading of the bbl which no one ever wants.

[gypsyman]

Obturation of a bullet will have something to do with accuracy and leading.

[rickt300]

I have shot a bunch of bullets unsized with no ill effects and very good accuracy.

[PWHeyes]

I shoot a .45 Schofield made in 1876. I have been using cast .454 230-grain bullets from Montana Bullet Works in it and getting excellent results (much better than I get in my Uberti Schofield clone, which has never been satisfactory). I was rather dismayed to find that Montana Bullet Works no longer stocks a 230-grain bullet in the .454 diameter. I understand that using a .452 diameter will cause tumbling and consequent inaccuracy.

I looked online and there are plenty of 230-grain .454 bullets available, mostly from Speer, but these would be commercially "speed"-cast, subject to variations in weight and balance, and I'd rather not use them

I have written to Bruce at MBW to ask for help, but was wondering if anyone here has suggestions. I don't have the facilities to cast my own bullets, so am looking for something to buy.

[gifbohane]

I bought an NOE 359-121-RN-R-3 mold to cast 9mm. 9MM translates to a little over .354. Do you folks think that I have the right mold?

[Rapier]

First thing is slug your barrel, always get ihe exact groove diameter, size to the groove diameter or no more than .001 over. Cast bullets without a hollow base, do not obturate....expand with pressure.

If you have a messed up barrel, big, little, big, well not very much is going to help that, but a rebore or new barrel. Cast shooting for accuracy at any longer distance requires good, clean and smooth, grooves and lands.
You can throw rock and hit a can at 10 feet.

[300leonidas]

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.



I greatly appreciated your post. There is a lot of good info in there! I made a chamber cast of my old 30/40 Krag. See attached image. Based on everything you've said, I would be well suited to size my cast bullets to .311. Correct?

It seems a lot of people recommend that the front end of the cast bullet "kiss" the lands. I take that to mean it should almost touch. Maybe .001-.002 away from touching? The front part of the boolits I've been making will never touch the lands because the only part that measures .311 is the part inside the case. The entire front half of my boolits measure around .300". Only the portion inside the case measures (or will measure after I size them to .311) large enough to fit snug in the throat.

Is that a problem?

310235

[deltaenterprizes]

Don't you guys mean to size larger than groove diameter?

I was just wondering about that!