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Thread: Slugging A Barrel

  1. #1

    Default Slugging A Barrel

    Just wondering how many of you have ever slugged a barrel, to determine actual groove diameter?

    What prompted this is I have a Marlin 1895 in 45/70 (actually, I have two of them...an older one with micro-groove rifling, and a newer one with ballard rifling), and recently tried some cast, plain base, 340gr bullets made in a Lee mould. They dropped from the mould right at .457 diameter (wheel-weight lead), so there was no way I could size them to .458, or .459. (would have preferred .459) I tried them anyway, with a modest charge of IMR 4198, driving them to about 1300 fps. Accuracy was extremely poor...couldn't hit the broad-side of a barn, from INSIDE the barn! (ok...a slight exaggeration, but you get the idea) The highest velocity reading on my chrono was about 1380 fps, with all the rest being less. (but still more than 1200 fps)

    The barrel suffered extreme leading after about 10 shots, and had to be brushed out with a bronze brush, to get all the lead out. (yes...the bullets were lubed properly) This was with the older rifle with the micro-groove rifling. I didn't have time to test the newer gun, which might have been perfectly happy with those loads...

    After some contemplation, I did some searching on the web to see if anyone else had suffered the same problem. Yep...plenty of them! Turns out the groove diameter for the Marlin 45/70 is spec'd at .4587" diameter, not .457". If that is the case, then trying to shoot .457" bullets through them isn't going to work out too well. I can just imagine all the high temperature gas blow-by....

    This lead me to wonder how to slug a barrel, to find out for sure. I found a couple "how-to" videos:

    http://www.youtube.com/watch?v=ErFaJlUVs1Y

    http://www.youtube.com/watch?v=CR_WiL8Dkgw

    Both videos appear to know what they are talking about, so I'm gonna give it a whirl with my Marlin and see what's up with this barrel...

    So...who has slugged a barrel? Did you do it the same way these guys teach, or some other way? Can you use a regular lead bullet, instead of a round ball? What if I "fatten" up one of those 340gr slugs a few thousanths or so in a vise, then try to use it as the "slug"??? (I don't have a 45-cal lead ball)

    Your thoughts?

    Marshall/Ak

  2. #2
    Member broncoformudv's Avatar
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    I have never slugged a barrel but plan on doing my 44 soon as I would like to start shooting cast bullets as well.

    Were you using gas checked bullets? Do you know the hardness of the lead you shot?

    There is a lot of good info on this on Montana bullet works website and they also produce a good booklet on shooting cast bullets.
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  3. #3
    Member Alangaq's Avatar
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    The easiest way to slug a barrel is with a pure lead muzzle loading ball. Just pound that puppy into the end of the barrel with a wood mallet and then pop it out with a cleaning rod.

    My advice is to forgo the slugging as all it will really do is confuse you…. If you want to shoot cast bullets in your 45/70 order yourself a RCBS 45-405 mould and pick up some gas checks. Use a .460 size die to lube them.

    Your Lee bullets will shoot a lot better if you bump your pressure up enough that they will obturate and seal you bore better. You got a bunch of leading because you are using WW alloy which is pretty hard for the low pressure load you are shooting so you got gas cutting and blow-by due in part to the small bullets. Lube has got nuthin to do with it, so don’t worry about your lube. So either go softer with your alloy or bump up your pressure, or ideally, buy a Lyman or RCBS mould. Try RL #7

    http://castboolits.gunloads.com/ is the end all do all cast bullet forum. Check them out!
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  4. #4
    Member Alangaq's Avatar
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    A couple more thoughts for you…..

    Do NOT try to use one of your WW alloy bullets to slug your barrel… it will get stuck BIG TIME and you will be hating life trying to pound it out of the barrel. If you can wait about a week until I get back in town, send me your address in a pm and I will mail you some musket balls.

    Also, 1300 fps isn’t too poopy…. My black powder loads with 405 gr bullets out of a 16” barrel run about 1200 fps.

    I can also send you a hand full of RCBS 45-405’s to try if you want.


    Let me know…..
    “You’ve gotten soft. You’re like one of those police dogs who’s released in to the wild and gets eaten by a deer or something.” Bill McNeal of News Radio

  5. #5
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    Default Slugging

    You can drive a soft lead bullet or ball into the muzzle and then knock it back out with a cleaning rod as suggested easily enough with a bolt gun but it is not so easy with a lever gun where you may have to drive the slug down through the barrel out the breech end. Use a SOFT lead ball in an oiled bore and use a piece of steel rod as close to bore diam. as possible. I use drill rod for smaller calibers.

    It appears a lot of .45-70 barrels are significantly larger than .457. I'll slug my .458 just for grins and see what it runs.

    I recently slugged my ".404 Express" to see if it was a .40 cal or .416 caliber and i've got a 8x57 to slug to see if it is a .318 or 323 bore. Slugging can be usefull but it can also be confusing as noted.
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    Hmm, I consider my self still a beginner/newbie at all this kind of stuff but don't find slugging the bore and the results to be confusing at all. In fact I find it clears things up, especialy when it comes to cast boolits, etc. I just slugged my Redhawk 45 Colt again and my Puma 454 levergun with a 20" barrell. I had used a round ball previously but I don't think it was quite big enough. I used an egg shaped sinker with the hole running lengthwise this time and it was perfect for these 45's. I oiled up the bore and hammered/tapped them through with a shotgun cleaning rod wrapped with tape every few inches. Here are a few pics. You can see the round ball barely has the rifling on it.



    Getting ready...


    Redhawk 4inch barrel 45 Colt. .451 bore



    Puma 92 454 Casull 20 inch barrel .452 bore


  7. #7
    Member 1Cor15:19's Avatar
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    Quote Originally Posted by Snyd View Post
    Hmm, I consider my self still a beginner/newbie at all this kind of stuff but don't find slugging the bore and the results to be confusing at all . . . I had used a round ball previously but I don't think it was quite big enough. I used an egg shaped sinker with the hole running lengthwise this time and it was perfect for these 45's. I oiled up the bore and hammered/tapped them through with a shotgun cleaning rod wrapped with tape every few inches.
    Maybe this is too strong of a word, but this sounds like a GENIUS idea! I've not used these for this before, but I'll certainly file this away in the ole gray matter and use it next time. Thanks Snyd.

  8. #8

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    Thanks guys for all the tips and info. I'll try to answer the questions all in one reply:

    1. These 340gr bullets are plain-base, not gas checked

    2. No, I don't know the lead hardness. It is from melted wheelweights. (The ones with the steel clip that hammer onto the rim) All I know for sure is that they aren't pure lead...they are harder...

    3. RE: the RCBS 405gr mold, with gas check. I already have one, and this bullet (cast from wheel-weights) shoots very well in either of my 45/70's...no problems, good accuracy, and no leading. All of these bullets I had sized to .459, and they shoot well...all of them. However, I load them to around 1700fps; recoil is downright punishing. I am trying to get a lighter bullet at more moderate velocity, for plinking and informal target practice. (and less kick!) Trying to get away from using gas checks also for the lighter bullet, because gas checks are not cheap. I do appreciate the offer from Alangaq to have some RCBS 405's shipped to me to try out...already gottem, but thank you!

    4. I don't see why slugging a barrel would be confusing. What would be so confusing about it? The process appears to be very simple. I would think knowing your barrel groove diameter would be very helpful information...especially for someone who casts their own bullets. (which I've been doing off-and-on for 40-some years) Just for whatever reason never got around to slugging a barrel...

    5. I agree with 1 Cor 15:19.....Snyd's idea is a spark of GENIUS: Egg-sinkers!!! Now why didn't I think of that? I will get a few of them and try those in-lieu of the soft round lead balls. (which I don't have) Sinkers are made out of pure lead, so they should work just as good. And...Snyd is a pretty fair photographer as well...his close-up photos really helped clarify the process...thanks Snyd!

    6. I don't know where I could find a .460 sizer die. All I can find online for 45 cal rifle are .457, .458, and .459. I have the RCBS Lube-a-matic tool, and almost always use the .459 die. I'd try a .460 sizing die, if I could find one, but don't see how that would help if the bullets as-cast are dropping from the mould at .457....

    7. Next experiment: to try the undersize .457 bullets in my other Marlin, the one with the ballard rifling. Not sure what Marlin specs the groove diameter for these newer guns...maybe the only thing different is the rifling...

    8. Bottem line: things might come down to this: Ebay....here I come, with a very lightly used Lee bullet mould, 340gr 45-cal plain base...looks like new...

  9. #9

    Default right sinkers

    when buying the sinkers, make sure you get the LEAD ones and not the "environmentally friendly" non-lead ones that look the same. it's an easy mistake--- trust me.

  10. #10

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    radman is correct: the "non-toxic" sinkers do look pretty much the same...I almost bought a pack before I saw the writing on the pack that said "contains no lead". They are brighter in color, like freshly cast lead that hasn't had time to oxidize. I don't know what they make them out of, but there isn't any lead in them. The real lead sinkers will gradually take on a darker grey color as the surface oxidizes. I'd just read the package, and avoid anything that says "environmentally friendly".

    Marshall/Ak
    "I love my country...it's the government I'm scared of"

  11. #11

    Default Results...

    Ok folks, here's the deal:

    I just slugged both of my Marlin 1895's using Snyd's method of using lead sinkers. It works perfectly. And it was relatively easy. The only hitch I ran into is that the sinkers I chose were slightly smaller than the bore (Danielson lead egg sinkers, size #8) I solved this problem by "squishing" the ends closer together (shortening the sinker, but making it fatter) in the jaws of a vise-grip pliers. A table vise would probably work just as good, but don't over-do it.

    It was easy to tap the sinkers into the end of the barrels until flush, then push them out the receiver end with an aluminum shotgun cleaning rod. It was interesting to note that pushing through the "micro-groove" rifling of the older gun was somewhat harder than through the ballard rifling of the newer one. (less friction?) Still, I did not need to "tap" the rod through the barrel...just a good steady shove was all that was neccessary.

    Be extra careful when measuring, as it is so easy to make a mistake at this point. Remember, the riflings on a bullet (slug) are a mirror-image of the barrel, so are "inside-out". You want to measure the widest point on one side of the slug to the widest point on the opposite side. This will be the groove diameter of your barrel. I found this was easiest to determine by setting the caliper jaws to just slightly over slug size, then closing the jaws very slowly, while at the same time rotating the slug slowly between my thumb and forefinger. Then when I felt the slug just barely "tugging" while rotating it, I knew the widest points of the slug were contacting the jaws, so took my reading there.

    (Warning: if you can't still rotate the slug, then the jaws are too-closed, and the reading will be in error, because the jaws have fallen into the grooves created by the barrel rifling...a lesser distance than the groove diameter. That makes it unable to rotate.)

    Remember, you are not measuring convenient flat surfaces...they are rounded due to the roundness of the barrel, but it's not really all that difficult...just take your time. I found it easier to use a micrometer than a caliper (because it was far easier to adjust while rotating the slug) but either will work.

    Results:

    Marlin 45-70 micro-groove barrel: .4585"
    Marlin 45-70 ballard-rifled barrel: .4567"

    Now...having finally slugged a barrel, I can see one potential problem with this procedure: let's suppose your barrel has an odd number of lands and grooves. While the process of tapping a sinker through the barrel will still be uneventful, measuring the result will be very problematic. In this scenario, you will have a groove on one side of the slug, and a land on the other! Seeing as how you need to measure groove to groove, and not groove to land, how then are you going to do the measurement accurately, since the nearest opposing groove will not be directly opposite on the slug (the farthest point away), but rather will be offset to one side or the other? If any of you know the answer to this one, please clue me in...

    However, everything should be hunky-dory and good-to-go with any barrel with an even number of lands and grooves...no problem.

    While I have not tried the newer Marlin yet with cast bullets, just knowing the groove diameter is smaller makes me believe it will very likely shoot better than the one with the micro-groove barrel. At least with those cast bullets measuring .457"


    Marshall/Ak
    "I love my country...it's the government I'm scared of"

  12. #12
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    I know it is not needed in this thread but to keep it going Here is how to measure a odd grove slug.

    To measure a slug with an odd number of groves you need a V-block of approximately the correct angle for the number of groves.

    Attached is a picture of how the setup and math are done. The Alpha angle of the block need not be exactly the Ideal Alpha angle, it just needs to be close enough that the outside of the slug rests against the V-block. However, the exact angle of the V-block should be used in the calculations. Since there is no good way to directly measure the "v" value of the blocks, place a round object of known diameter in the block and measure "h" then calculate "v" using Equation 2. Then measure your slug and calculate Diameter using Equation 3.
    Attached Thumbnails Attached Thumbnails 100_1848_crop.jpg  

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