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Thread: FYI This is how I do a pound cast.

  1. #21
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    Good job, Tim. I think that gets the idea across pretty well.

    One thing I do differently, though I doubt it really matters that much, is use WW alloy to fill the case rather than pure. Sometimes the shoulder telescopes a bit during the pounding, and WW alloy helps support it a bit more. Heating the entire case with a torch helps get the bubbles out for sure, as does tapping the case while heating. One thing that I've found really helps is to use a case that was fired in that particular chamber, UNsized. Point muzzle up when inserting the pound slug because the boolit will fall out of the unsized neck otherwise.

    Here's an article I wrote elsewhere describing essentially the same thing:



    Part one:

    Following the statement "Fit is King" and considering first the static part of fit, we must learn exactly what is the dimensional goal we wish to achieve with our fixed ammunition. The most logical method I've found to do this is to make a sturdy impression of the rifle's chamber and throat from which detailed measurements can be taken.

    While several common methods exist to cast impressions of chambers, I personally prefer the impact or "pound casting" method, and will limit my own discussion here to this type. (everyone else feel free to add descriptions of other methods that work for you) This method was invented, I believe, by some clever cast-bullet shooter friends of mine who were seeking an inexpensive and simple method of getting the rifle's critical internal measurements without the hassle associated with pouring molten Cerrosafe, sulphur, or other things directly into the chamber.

    Essentially, a "pound cast" is made by installing a lead-filled cartridge case and malleable slug into the chamber and throat, locking the breech, and expanding the whole thing to fit the chamber and throat area completely via hydraulic force applied by a rod inserted through the muzzle. Here's a step-by-step general idea of how I do it, which is by no means intended to be comprehensive or absolute.

    1. Clean the rifle's chamber, throat, breech face, breech locking mechanism, and bore with brushes and solvent, dry and put a thin film of oil the chamber and throat. Use a HEAVY oil, such as gear lube or case lube to prevent sticking and make it easier to extract the slug after forming. Apply grease or oil to the locking mechanism per normal lubrication practices.

    2. Obtain a roll of vinyl electrician's tape, a brass or steel rod longer than the barrel but that will insert into the barrel when wrapped in one layer the tape, a medium hammer, a gas check of the caliber of the gun being casted, a sacrificial cartridge case that has been fired in the gun and still has the primer intact, a propane or other hand-held torch, large spoon, a heavy-for-caliber bullet mould or slug mould made with a bore-diameter hole drilled in a piece of hardwood, enough pure lead to cast several heavy (long) bullets or slugs, enough wheel weight or similar-hardness alloy to fill the cartridge case, and some pliers.

    3. Melt the wheel-weight (or similar) metal in the spoon with the torch, heat the top half of the case enough to anneal it (dull glow ok, and pour the molten metal into the case while it's still hot. Fill to about halfway up the neck with the alloy and allow it to cool. Grasping the case with pliers and gently lifting and tapping the case head on a solid surface and re-applying heat to keep the alloy melted for a few more seconds will help dislodge air pockets and settle the alloy.

    4. Using the same spoon, cast some heavy bullets using pure lead, or make a slug mould that will cast a cylinder of bore diameter that is about 1/2" longer than the longest "standard" bullet the gun is intended to fire. This is a general idea, you just want enough metal to fill what's left in the case neck, the whole throat, and the origin of the rifling.

    5. Clean and oil the alloy-filled case, oil and install the dead-soft bullet or slug into the mouth by hand, and insert it into the chamber. Force the action closed behind it and place the gun muzzle up with the buttplate on a firm, non-marring surface (like a clean work mat or cardboard).

    6. If a gas check is available, start it into the muzzle squarely with a punch, concave side up. Wrap the metal rod with a closely spiraled, single layer of electrician's tape to protect the bore, and build bore-diameter "bushings" for a reasonably snug, centering fit on the ends and middle of the rod if one layer of tape isn't sufficient to support the rod in the center of the bore. Use the rod to push the check all the way to contact the slug, making sure the tip of the rod is captured inside the cup of the check and that the check hasn't gotten turned sideways. Sometimes a fired .22 rimfire case or pistol cartridge case can be used instead of a gas check depending on the caliber of the rifle. The object is to keep the tip of the rod from sinking and sticking into the soft lead. The check provides a sort of piston and separation point.

    7. Hold the rifle and support the rod at the muzzle securely with one hand, and firmly tap the end of the rod with the hammer to compress the alloy and annealed case within the chamber. You should be able to feel the rod sink as the metal swages to the form of the throat and chamber, and suddenly the blows should begin to feel very solid. Once it feels like the rod isn't going to go any deeper, invert the gun while holding the rod in place, place the tip of the rod on a solid surface (floor) and open the breech while leaning on the buttstock to apply pressure to the rod. Pushing on the rod while opening the breech will aid in extraction and help prevent broken extractor mechanisms.

    8. After removal, inspect the pound cast for complete fillout. It doesn't have to be pretty, just filled enough to measure accurately in the critical places such as both ends of the neck, total chamber length, throat entrance, and the entire throat up through the ball seat and into the full land height.

    9. Now you have something to measure and keep around that won't shrink, dry out, or change with time, and will have a much better idea of the fit parameters of the particular rifle.

    Here's a not-so-great picture of several pound casts together with some ammunition built to closely fit the chambers and throats based upon them. Should be close enough to get the idea.




    Gear
    You can't fix Stupid, but you can occasionally head it off before it hurts something. --Stephen Adams

    To universalize one's experience and state it as the norm is always thin ice on which to stand.--CharGar

    Being able to separate the wheat from the chaff has always been a valuable skill in all of life's activities. --Bwana


  2. #22
    Boolit Man
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    Once again Tim, Outstanding post. I don't have a say in the matters, but yes on the Sticky. From your original post I have filled the cases of my rifle brass as explained- even better now. I was just not real sure of the follow thru.

    Thank You

    Ghost101

  3. #23
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    So again, why did Tim bring this up? He's trying to help us make a tool for building better cast boolit ammunition for our rifles. Unlike jacketed bullets, our cast boolits are delicate and easily damaged during the reloading process and firing process, so we must support them any way we can to give them a proper, accurate launch.

    Here's a little more on that....

    Part II:

    Now that you have a chamber cast, what's next?

    I'll try to outline some of the things I do in a very general way, but much of it is subjective and dependent on the individual gun.

    The first order of business is to determine how large of a bullet the rifle will chamber and fire without scraping the bullet on the throat entrance. As I mentioned in the "Fit" article*, I've found the best accuracy usually occurs in rifles that have their bullets fitted very closely to the throat entrance dimension. This is not a fast rule for every rifle, but a general approach only. To obtain this measurement, simply measure the step in front of the end of the chamber, right against the base of the step, and PLEASE use a quality, name-brand 0-1" MICROMETER, not your Chinese calipers, ok?

    Next, I like to measure both ends and the middle of the neck to determine taper, if any, and the essential chamber neck dimension. Again, as mentioned in the "Fit" thread, the loaded case neck-to-chamber-neck clearance needs to be minimal, on the order of half a thousandth or so, and certainly less than one thousandth, for maximum bullet support during firing. Excessive clearance here is almost chronic with production rifles, and is probably the single most accuracy-destroying clearance of all of them.

    To establish how much loaded chamber neck clearance you will have, subtract two case-neck-thickness diameters and the throat entrance diameter from the average chamber neck diameter. For example, a .30-'06 chamber neck might measure .3435" in the middle, and brass is typically .0135" thick, or .027" total. The throat entrance is .3105". Subtract .027" and .3105 from .3435" and you will end up with .006". SIX thousandths total neck clearance is unfortunately common since it promotes safe chambering and firing of jacketed bullets and the jackets don't seem to mind being launched crooked or having a lot of gas blow around them before engraving, but cast bullets suffer mightily through this, ESPECIALLY at high velocity. I believe that this excessive chamber neck clearance is the principle reason why there seems to be such a low "accurate velocity" limit when shooting cast bullets in rifles, and why they are traditionally launched with low pressure charges of fast-burning powder. In the case prep thread I will explore methods of achieving smaller case neck clearance, and maybe in the #10 article I will discuss some techniques that sometimes improve accuracy when excessive neck clearances cannot be remedied.

    The next point of interest is the throat shape. Matching the bullet's nose profile as closely as possible to the throat dimensions and shape will greatly increase accuracy in most instances vs. a bullet that simply has a bore-riding nose and parallel driving bands sized to the "common knowledge" dimension of .001" larger than barrel groove diameter. This doesn't mean that two-dimensional bullets fitted well to the bore and throat entrance can't shoot well out of a gun with a long taper to the throat, for indeed they do sometimes, but generally it's more difficult to achieve or maintain accuracy as velocity is increased, or get excellent accuracy in the first place, if the nose isn't shaped like and fully supported by the throat when chambered and during firing.

    Notice that I didn't "slug" the entire bore and measure the groove dimension? That's because I base bullet size on throat entrance diameter, which is 99.5% of the time (H&R .38-55 being an exception) larger than groove and the chamber necks are almost always large enough to accept a cartridge loaded with a throat-entrance-diameter bullet.

    Those are the basics of bullet fit based upon pound cast dimensions, I'll describe more about fitting the cartridge case itself to the chamber in the case prep article.**


    Gear

    *"Fit Is King" is a separate reference not yet published here.
    **"Case Prep for Accuracy" is an additional article.
    You can't fix Stupid, but you can occasionally head it off before it hurts something. --Stephen Adams

    To universalize one's experience and state it as the norm is always thin ice on which to stand.--CharGar

    Being able to separate the wheat from the chaff has always been a valuable skill in all of life's activities. --Bwana


  4. #24
    Boolit Master slim1836's Avatar
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    Tim,

    Thanks for the education, clear, concise, and helpful.

    Slim
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  5. #25
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    Tim, if you get a chance, take a pic of a .308 cartridge loaded with a .310" cast boolit, with your mic on the case neck somewhere in the middle. I'll bet it's around .338", giving about .009" total clearance. With that much room, what do you suppose happens to the driving portion of the boolit when the powder is touched off? It's a wonder we can shoot as well as we do out of "factory" chambers, isn't it?

    Most "benchrest" competitors shooting jacketed bullets strive for half a thousandth or less clearance in the neck area. Much can be learned from them, but with production brass and factory chambers, close fit is usually impossible to achieve. There are ways, though, to either eliminate the fit issue or work around it, once one has made a pound cast and measured it as Tim described and pictured.

    My favorite new way to achieve proper loaded neck fit is to ship a barrel and action to Malcolm Ballistic Tool and have it built with a proper reamer, then just a light neck turn for final precision fit gets the last few "tenths" just right.

    Gear
    You can't fix Stupid, but you can occasionally head it off before it hurts something. --Stephen Adams

    To universalize one's experience and state it as the norm is always thin ice on which to stand.--CharGar

    Being able to separate the wheat from the chaff has always been a valuable skill in all of life's activities. --Bwana


  6. #26
    Boolit Master Garyshome's Avatar
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    Nice job! Good info!

  7. #27
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    Tim, your common hammer appears to be a 2 lb'er. Veral stated to use a heavy hammer with light blows and that a light hammer with heavy blows was a sure reciepe for a stuck rod. Good write up, i have used 2-4 lb hammers but use whatever heavy your wrists will allow.
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  8. #28
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    Yes, HEAVY hammer, light but firm taps. Hitting the rod end squarely and firmly, with controlled follow through is also important, same as it is with a golf or bat swing. 6-8" lead-off with the hammer does it. No using a tack hammer and swinging from behind the head!

    Gear
    You can't fix Stupid, but you can occasionally head it off before it hurts something. --Stephen Adams

    To universalize one's experience and state it as the norm is always thin ice on which to stand.--CharGar

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  9. #29
    Boolit Master

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    Great stuff fellers!
    Ian, I really appreciate your input.
    I wouldn't even know how to do this if it weren't for several conversations we had a couple years ago. Thanks for all your help.
    Tim Malcolm
    MBT custom rifles & gunsmithing
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  10. #30
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    Texasmac has also done an excellent article on impact casting and other methods which is linked here on Cast Boolits which is well worth a read.

    http://www.texas-mac.com/Discussion_...mpression.html

    Rather than use a gas check I put a plug of kitchen towel down on top of the slug, this forms a compact plug that stops the rod depressing into the bullet and the chance of lead flow round the base of the rod. It just pops out with the impact cast and there is no risk of getting a copper ring lodged in the barrel


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  11. #31
    Boolit Master

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    Thanks for the tip adam. I never heard of using a wad of paper before, but it makes sense.
    Actually, when I do this for myself, I make a brass plug that fits the bore exactly and solder it on the end of the rod. It's perfect, but unfortunatley, most members do not have access to a lathe, so I did it the old fashioned way.
    If anybody has the ability to make a custom fit driving plug, that is by far the best way to do it. However, the GC works in a pinch.

    I confess I didn't know about the weight of the hammer. I just used a pretty good sized whacker bonker to get the job done, but I can see how the lighter ones would give bad results.
    Good stuff fellers!
    Tim Malcolm
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  12. #32
    Boolit Master freebullet's Avatar
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    Excellent thread, & a fine example of why I joined this forum instead of lurking off info. Thank you, its priceless.

    I have a question though.
    In the photos there is a lot of lead just ahead of the case neck. Is that how long your case length could be in that weapon? As in potentially eliminating needless case trimming?

  13. #33
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    Quote Originally Posted by freebullet View Post
    Excellent thread, & a fine example of why I joined this forum instead of lurking off info. Thank you, its priceless.

    I have a question though.
    In the photos there is a lot of lead just ahead of the case neck. Is that how long your case length could be in that weapon? As in potentially eliminating needless case trimming?
    It depends, but usually so. One can tell by measuring with calipers the approximate length of the chamber on the slug how long the brass can be. Most chambers are rather "generous" in all directions. Simply observing the brass/lead line on the pound cast can be a bit deceiving since the case mouth can flow back slightly as the impression is made.

    Look at the picture I posted above and you can sort of see the chambers vs. brass length.

    Gear
    You can't fix Stupid, but you can occasionally head it off before it hurts something. --Stephen Adams

    To universalize one's experience and state it as the norm is always thin ice on which to stand.--CharGar

    Being able to separate the wheat from the chaff has always been a valuable skill in all of life's activities. --Bwana


  14. #34
    Boolit Master
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    yep that is really how long the chambers neck is.
    quite often they will end with a little taper here and not an abrupt square edge.
    the little taper there gives you a mis-leading look at things so you need to put the mic on it too to be sure of how long your brass can be.
    many are surprised to find they have been doing all that work trimming their brass only to find out their chamber will take .xxx longer brass than they have been making.

    if you don't fill this area with brass the boolit might be trying to when you fire the cartridge this is called riveting.
    it's all an educated guess,,,, till the trigger is pulled.

    this opinion brought to you by mister low-tech solution..

  15. #35
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    QUESTION?

    You have annealed the neck of the cartridge case.
    Does the neck of the cartridge case expand to fill the neck of the chamber ?

    That would also be good info to have.
    First reload: .22 Hornet. 1956.
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  16. #36
    Boolit Master

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    Quote Originally Posted by williamwaco View Post
    QUESTION?

    You have annealed the neck of the cartridge case.
    Does the neck of the cartridge case expand to fill the neck of the chamber ?

    That would also be good info to have.
    Yes. That's the whole reason for annealing it dead soft.
    Also, that is mil-spec brass, untrimmed and correct length. Measuring from the head of the cartridge to the end of the full neck diameter is 2.050 in this slug.
    Spec is 2.015 max length on the 308.
    If anybody here paper patches and finds rings of paper left in the chamber after the shot, you might be surprised to find that ring to be exactly the same as the distance from the end of the case mouth to the end of chamber. Cosmic coincidence? I think not.
    Until you do a pound cast, you know nothing about the true nature of your chamber and how your brass fits in there, and how your boolit fits the throat.
    Cerrosafe just doesn't give that to you.
    Tim Malcolm
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    "He who is enslaved by the compass has freedom of the seas"

  17. #37
    Boolit Master
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    Shoot full of holes? Baloney! You've given us a very good method, described in detail of how to get a "cast" of some critical dimensions of our guns. I have seen other methods, but like the "goodsteel" method quite a bit. Thank you...
    My Anchor is holding fast!

  18. #38
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    Cerrosafe actually works pretty well, but you really have to pay attention to age time and use the shrinkage chart to get accurate measurements. The pound cast is basically free and permanent. Less messy too.

    Gear
    You can't fix Stupid, but you can occasionally head it off before it hurts something. --Stephen Adams

    To universalize one's experience and state it as the norm is always thin ice on which to stand.--CharGar

    Being able to separate the wheat from the chaff has always been a valuable skill in all of life's activities. --Bwana


  19. #39
    Boolit Master

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    Bump for a friend
    Tim Malcolm
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  20. #40
    Boolit Man
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    Thank you for the pictures. Very helpful. I have my brass full of lead per one of your posts but haven't followed thru with everything else.
    GoodSteel thank you once again for teaching me.

    Ghost101

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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