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Thread: Cast bullet size

  1. #21
    Boolit Master Outpost75's Avatar
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    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.
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  2. #22
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    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

  3. #23
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    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.
    I give loading advice based on my actual results in factory rifles with standard chambers, twist rates and basic accurizing.
    My goals for using cast boolits are lots of good, cheap, and reasonably accurate shooting, while avoiding overly tedious loading processes.
    The BHN Deformation Formula, and why I don't use it.
    How to find and fix sizing die eccentricity problems.
    Do you trust your casting thermometer?
    A few musings.

  4. #24
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    or that's what one of us said, and someone else just wanted to argue.

  5. #25
    Boolit Mold
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    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?

  6. #26
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    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.
    I give loading advice based on my actual results in factory rifles with standard chambers, twist rates and basic accurizing.
    My goals for using cast boolits are lots of good, cheap, and reasonably accurate shooting, while avoiding overly tedious loading processes.
    The BHN Deformation Formula, and why I don't use it.
    How to find and fix sizing die eccentricity problems.
    Do you trust your casting thermometer?
    A few musings.

  7. #27
    Boolit Master Char-Gar's Avatar
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    Quote Originally Posted by Outpost75 View Post
    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.
    Disclaimer: The above is not holy writ. It is just my opinion based on my experience and knowledge. Your mileage may vary.

  8. #28
    Boolit Master Outpost75's Avatar
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    Quote Originally Posted by Char-Gar View Post
    ___________________________________________

    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...
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  9. #29
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    Ok, I'll make this a sticky.

  10. #30
    Boolit Master Outpost75's Avatar
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    Quote Originally Posted by JonB_in_Glencoe View Post
    Ok, I'll make this a sticky.
    Merci Beaucoups!
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  11. #31
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    so does a bore riding portion of a bullet bump up to fill the groves when fired?
    ..

  12. #32
    Boolit Master Char-Gar's Avatar
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    Quote Originally Posted by Beerd View Post
    so does a bore riding portion of a bullet bump up to fill the groves when fired?
    ..
    Nope!
    Disclaimer: The above is not holy writ. It is just my opinion based on my experience and knowledge. Your mileage may vary.

  13. #33
    Boolit Master Outpost75's Avatar
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    Quote Originally Posted by Beerd View Post
    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!
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  14. #34
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    So was JM Browning the Easter Bunny and Winchester the Mothman, or the other way around?

    But somehow they made it work.
    I give loading advice based on my actual results in factory rifles with standard chambers, twist rates and basic accurizing.
    My goals for using cast boolits are lots of good, cheap, and reasonably accurate shooting, while avoiding overly tedious loading processes.
    The BHN Deformation Formula, and why I don't use it.
    How to find and fix sizing die eccentricity problems.
    Do you trust your casting thermometer?
    A few musings.

  15. #35
    Boolit Master Outpost75's Avatar
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    Quote Originally Posted by HangFireW8 View Post
    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.
    The ENEMY is listening.
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    Keep it to yourself.

  16. #36
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    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.
    I give loading advice based on my actual results in factory rifles with standard chambers, twist rates and basic accurizing.
    My goals for using cast boolits are lots of good, cheap, and reasonably accurate shooting, while avoiding overly tedious loading processes.
    The BHN Deformation Formula, and why I don't use it.
    How to find and fix sizing die eccentricity problems.
    Do you trust your casting thermometer?
    A few musings.

  17. #37
    Boolit Master Outpost75's Avatar
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    Quote Originally Posted by HangFireW8 View Post
    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.
    Last edited by Outpost75; 03-26-2018 at 11:34 AM.
    The ENEMY is listening.
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  18. #38
    Boolit Master vrh's Avatar
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    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.
    Da Okie/ Now known as Vearl

  19. #39
    Boolit Mold
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    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.

  20. #40
    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.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check