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Thread: Need advice on a mold

  1. #11
    GunLoad Trainee
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    The education continues, thanks for all the input. I have slugged two of my three rifles. Discovered one is a two land and the other is a five land barrel. This time I used the 1/4 oz oval fishing sinkers. A lot easier than trying to drive the 158 grain hard lead through.

    I found an article that suggested that a wood dowel be placed in the barrel and the slug driven down on it so that progress was blocked and the lead would flatten to fill the barrel's groves completely before it was driven all the way through. And I did that. However, visually, it appears that the diameter of the slug is greater on the driven end than on the front and I am having a tough time getting readings that I have any confidence in. I have slugged each barrel three times. It is oblivious that I don't have any experience at this point. I may have to ask someone else to look at these tea leaves and read them. Anyone want to try?

    Am I missing something here? The oval sinker flattens out wider than the barrel and it seems that it should be a good indication of the barrel diameter. There is excess lead that is trimmed off as the slug is driven into the barrel. The slug is not that difficult to drive through but it is greater than hand pressure. Think I am getting the total diameter?

  2. #12
    Dogs Like Him versifier's Avatar
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    Yes, you're doing it right. That's what's supposed to happen. There is no need to drive it into a dowel, though (that's something you do when you don't have a slug that's large enough in diameter.) Just forcing the slightly oversize slug down through the bore is enough to give you good readings. It doesn't take a lot of force unless there is a constriction in the barrel, but it needs more than you can apply by hand. A little patience now will save you hours of casting and lots in components later on.
    "Stand your ground.
    Do not fire unless fired upon.
    But if they mean to have a war let it begin here."
    - Capt. Parker, Lexington Militia, April 19, 1775

  3. #13
    runfiverun runfiverun's Avatar
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    if you mashed it out like the instructions said and are getting pretty consistent readings you should be fine.
    the two groove bbl is gonna be a pain anyways [trust me]
    i'd concentrate on the 5 land bbl,it's hard to measure the diameter of them but you need to have an idea as then you can exceed it.
    this all sounds like a pita right now but you at least have an idea of where to start.
    now to fill the throat area.

  4. #14
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    Saw this on a 8/31/09 post over on Cast Bullets:

    "just checking, but you do know that you can't just put the slug in a micrometer and measure it due to the 5-groove barrel? If you do that, they do tend to come out at around .308", but that doesn't actually tell you anything useful. "

    I have to agree that it is difficult to measure the 5-groove slug, but there has to be a secret. How does everyone do it.

  5. #15
    Dogs Like Him versifier's Avatar
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    Ah, grasshopper, you have discovered the curse of S&W (and others). One method uses a v-block and is generally more accurate, the other uses a depth mic with accuracy dependent on how well you can use the tool. If you search over on CB, you will find pictures and diagrams of several different setups, or ask in a post and someone over there will find the right thread for you. Some smartass with a dividing head invented the five groove rifling configuration that has been aggravating casters for generations. Just in case you happen to have discovered his/their name(s), don't tell me, I can curse them more effectively and I cherish my ignorance.

    My way is easier but you need another tool. I use a depth mic to carefully measure groove depth/land height. The slug is first measured groove to land, which gives you bore diameter + one land. Measure the depths of all 5 grooves with the depth mic and add their average to your first measurement to get groove diameter or subtract it to get bore diameter.
    "Stand your ground.
    Do not fire unless fired upon.
    But if they mean to have a war let it begin here."
    - Capt. Parker, Lexington Militia, April 19, 1775

  6. #16
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    Well I have made a little more progress. For the two groove barrel, I have made numerous measurements on three different slugs. No big variations between the readings; the readings average 0.3163" So I assume I am looking for a cast bullet in the range of 0.3180 to 0.3190"

    The five groove barrel, well I am still working on it. I found some 0.001' shim stock and I am doubling it and wrapping it around. First measurements indicate around 0.3112-0.3113". The bore does have a mirror finish and may be that tight. As I said before, still measuring.

    Runfiverun threw me a piece of bait, guess it is time to bite. He mentioned filling the throat area. Is the throat more important than the bore? How do I determine the throat diameter? I read somewhere that the inside diameter of a fired case would be a good indication of the throat area. Is that an acceptable way? Need a little guidance along this next segment of my journey.

  7. #17
    runfiverun runfiverun's Avatar
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    measuring inside the case will tell you how big of a boolit will chamber.
    the throat is a bit more complicated you want to try and mimic the shape of the throat as much as possible.
    your boolit and throat look like this ...>>.
    best way to "see" it cerrosafe.
    or just through experience i guess.
    your boolit doesn't have to be grossly oversized to your bbl but it does have to fit it.
    if your bbl is say 311 you can get away with 3115 or 312.
    the boolit fittting the throat helps it align straighter and grip the rifling better without slipping [skidding] if you are gripping the rifling from the start it makes life easier on the gas check and it can do it's job better and help the boolit maintain it's grip in the bbl and exit straighter.
    not even gonna start on slump,alloy and lube yet. fit is what you want to learn first.

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BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
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HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
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LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
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