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Thread: New full bore slug

  1. #1
    Boolit Grand Master


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    New full bore slug

    I ended up buying cast bullet design software, made by member Tom Myers. I got the basic, and it works well enough, I'm not sure it's worth its price though. I was under the impression it could estimate ballistic coefficient's, but it seems only the professional version may do that. Anyway, I decided to use it to draw a slug I've had rolling around in my head for a while. I wanted to get the longest bearing surface I could on it to reduce the jump to the rifling as minimal as possible. I hoped to keep it a bit lighter, but 725-760 grains depending on alloy is ok. Taking a cue from other bullet designs, I put a meplat of .500", just over 68%. Small meplat's are a complete waste on a shotgun slug, and is my biggest fault with my Accurate 73-770S. I feel like a tangent ogive with no shoulder should provide the best self-aligning in this case. I'm not scared of the slug jumping the crimp at all, most factory rifled slugs are the same without problems. Along with the weight thing, I wanted the lightest weight I could, so I think a hollow base is the best way to do that. The walls should be plenty thick, and nose left thick so that it does not deform on firing or impact. I'm not sure how the balance will effect it, I would think if anything it would help. Anyway, here is the slug I'm hoping to have Tom (Accurate molds) make, and then sent for a hollow base pin. Don't be afraid to criticize. Presumably, I could have multiple base pins made. How thin do you think I could go?

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    Last edited by megasupermagnum; 04-23-2018 at 12:54 AM.

  2. #2
    In Remembrance bikerbeans's Avatar
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    Mega,

    One thing to check is Tom has some dimension restrictions on depth of the grooves and the angle of the grooves. I don't remember the numbers but if you open his design a mold it lists them.

    The wider the nose the better in my book. Easier to roll crimp and makes a big hole.

    Regarding skirt thickness, if you want the skirt not to collapse then I would plan on heat treating the slug. I know folks fill the cavities of the HB slugs, but in my mind that's just adding another variable to the load. Few components means fewer chances for error.

    I have a couple of HB slug molds and both base pins have tapered sides and a flat point. I know you want a fair amount of taper if you want the slug to release easily. I don't know why the point of the pin is flat.

    BB

  3. #3
    Boolit Grand Master


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    I agree, I never did like the idea of filling the cavity. I was either going to heat treat, or cast with linotype, probably heat treated 94/3/3 alloy. I should be within Tom's tooling abilites. The groove angles are 55 degrees, and the depth is the same as his other slugs. I did not see an option for a flat point hollow cavity in the program, although there is a decent taper to the whole thing. I'll mess around more, and see if I can't get a flat point, that may lower the slug weight even more.

    Edit:
    It seems the program can only do rounded top cavities, but I'm sure Erik at Hollow point molds can set me right. The very odd thing is as far as I can tell, I never touched anything, yet now it's telling me the estimated weight is 671 grains with the same alloy. I'm not sure how much I really trust the program, but that would be fantastic if true.
    Last edited by megasupermagnum; 04-23-2018 at 12:55 PM.

  4. #4
    In Remembrance bikerbeans's Avatar
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    94/3/3 alloy heat treats harder than blazes!

    HP Molds can make you a pin that will also allow you to cast a solid base slug. This is a good option in case you decide to hunt cape buffalo.

    BB

  5. #5
    Boolit Grand Master


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    No kidding. A plain base is calculated at 950 grains! Now the hollow base says 760 grains again, so I'm going to assume that is the weight with the hollow base shown. I've never heat treated anything, but I've water dropped some alloy. I had some lyman #2 water drop at 26 BHN, so I can only assume heat treated 94/3/3 should be close to linotype hardness. I certainly won't be seeing any expansion.

  6. #6
    Boolit Grand Master


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    Good afternoon
    That looks like death waiting to strike !
    What if it was poured from zinc ? I understand the desire not to contaminate a mold with zinc but it would be light and probably the skirts would withstand any pressure applied in a shotgun.
    Mike in Peru till June
    "Come unto Me, all you who labor and are heavy burdened, and I will give you rest." Matthew 11:28
    Male Guanaco out in dry lakebed at 10,800 feet south of Arequipa.

  7. #7
    Boolit Buddy uncle dino's Avatar
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    Mega ... BC is in lower rt hand corner. .12 looks about right for that slug..not sure if pic is from your software or accurate molds though..d

  8. #8
    Boolit Grand Master


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    Quote Originally Posted by uncle dino View Post
    Mega ... BC is in lower rt hand corner. .12 looks about right for that slug..not sure if pic is from your software or accurate molds though..d
    D'oh! Good catch. Now I'll be checking out different bullets for hours looking at the BC. I had to name the slug something, so I just put in an Accurate molds number. So far Tom has had nothing to do with it, I created that slug myself on a program that I'll link below. I'm hoping somebody will catch any mistakes of mine before I have the mold cut.


    http://www.tmtpages.com/draw/draw.htm

  9. #9
    In Remembrance bikerbeans's Avatar
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    Heat treating with the right alloy is easy. With 94/3/3 I use 450F for 30 minutes and immediately dunk them in a 5 gal pail of water. I use a cheap toaster oven and my thermo couple, SSR and PID to control temp. I drilled a hole in the top of the oven and insert the thermo couple right above the slugs.

    BB

  10. #10
    Boolit Grand Master

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    Looks okay to me though I think i'd go a hemispherical RNFP... but then I am thinking smoothbore. Things are a bit different for rifled gun.

    As for the HB and skirt, I'm with BB on it likely being best to heat treat. I haven't run into a skirt yet that hasn't deformed some if not heat treated no matter how thick it was, and still looked like an HB slug anyway. I fill the cavities partly to support the skirt but mostly to keep wads out of the cavity. Heat treated or not if the slug has a hollow base wads will try to get in there, even nitro card wads. You could copy the Lee Drive Key or get a tapered hollow bored/reamed into the core pin like the Russian Paradox slugs so the skirt could be thinner but the wad would be stopped by the central pin.

    I wouldn't go any thinner on the skirt than 0.100" ... at least without a pin or "key", but that's just me.

    If you don't fill or use the key/pin idea then put a tough disk like polyethylene under the slug. That should keep wads out.

    As for weight, you could lighten some by using just two driving bands and leave a wide, and deep as Tom can cut, groove. The old Paradox slugs had a huge groove! They were solid body so heavy even if they were HP'd but a hollow base design would lighten them a lot. I've always liked the Paradox design:

    https://www.classicshooting.com/coll...ant=1179491392

    I'd stay away from too large a flat on top of the pin. I made mine fairly flat so keep lead in the nose but if I don't tip the mould a bit while pouring I often get a little cavity at the top due to air trapped over that big flat. Bubbles seem to flow off a radius or point but seem to hang onto the flat... at least in my mould. I think your radius looks good.

    That slug would probably shoot just fine as is from rifled gun.

    Longbow

  11. #11
    Boolit Grand Master


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    Quote Originally Posted by longbow View Post
    Looks okay to me though I think i'd go a hemispherical RNFP... but then I am thinking smoothbore. Things are a bit different for rifled gun.

    As for the HB and skirt, I'm with BB on it likely being best to heat treat. I haven't run into a skirt yet that hasn't deformed some if not heat treated no matter how thick it was, and still looked like an HB slug anyway. I fill the cavities partly to support the skirt but mostly to keep wads out of the cavity. Heat treated or not if the slug has a hollow base wads will try to get in there, even nitro card wads. You could copy the Lee Drive Key or get a tapered hollow bored/reamed into the core pin like the Russian Paradox slugs so the skirt could be thinner but the wad would be stopped by the central pin.

    I wouldn't go any thinner on the skirt than 0.100" ... at least without a pin or "key", but that's just me.

    If you don't fill or use the key/pin idea then put a tough disk like polyethylene under the slug. That should keep wads out.

    As for weight, you could lighten some by using just two driving bands and leave a wide, and deep as Tom can cut, groove. The old Paradox slugs had a huge groove! They were solid body so heavy even if they were HP'd but a hollow base design would lighten them a lot. I've always liked the Paradox design:

    https://www.classicshooting.com/coll...ant=1179491392

    I'd stay away from too large a flat on top of the pin. I made mine fairly flat so keep lead in the nose but if I don't tip the mould a bit while pouring I often get a little cavity at the top due to air trapped over that big flat. Bubbles seem to flow off a radius or point but seem to hang onto the flat... at least in my mould. I think your radius looks good.

    That slug would probably shoot just fine as is from rifled gun.

    Longbow
    A lot of it was just done by eye, I think that nose looks right on there. I just want to try some kind of round nose to see if I can't squeeze that last bit of accuracy out of the gun verses a sabot or wad cutter type full bore slug. I've been getting consistent 5" groups with some coming down to about 3 1/2" with the Accurate 73-770S now that I've dialed the loads in better. I could keep trying for those sub 3" averages, but they don't seem as devastating as they should due to the small flat point. I have no doubt they are more than lethal, but if I'm going to punish myself in recoil, and they are in pain in the butt to cast, I may as well throw a hammer of a slug. Plus you can bet I'll try the hollow base in a smooth bore as well. That would really be some bear medicine!

    Back to the looks of the slug, I did try just one big lube groove, and it just looks wonky. If I want lighter weights, that slug says it should be about 725 grains when cast of linotype, and 740 gr with Lyman #2. I'm going to try some of the 73-770S's over the chronograph again soon, as I have a feeling I am getting awful close to 1300 fps with them and Bluedot. I gave up on Remington hulls, it turns out they are softer than anything. I got failures to extract at 34 grains. With Fiocchi hulls, I was starting to get an extractor dent at 36 grains which should be in the ball park of 11,000-12,000 psi. I've now gone to Federal hulls, and at 36 grains, they are spotless. I'm thinking of pushing it to 38 grains and seeing how fast that is.

  12. #12
    Boolit Buddy uncle dino's Avatar
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    I've had the pro edition for a year and I'm still learning...I do believe you can trick the program and do a flat base pin. It'll give you an error, but it'll still calculate.. I'll have to re check how I did it..d

  13. #13
    Boolit Buddy catboat's Avatar
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    I am interested in slug loading my 12 and 20 gapump shotguns. I’ve been reading and reasearching designs and loading notes from those who have done it,

    Looking at your slug design, one thought came to mind based on my reading. I seem to recall reading that it was beneficial to have a flat ledge on the outer front rim of the slug ( sort of like the shoulder on a Keith style bullet, but with a wadcutter,minimal pronounced center meplat). Evidently ledge this allows a roll crimp to release/unroll upon firing and not create pressure spikes if the accelerating slug( that does not have a flat rim ledge, and is more “ rounded” going from meplat to slug side like your design) would “ catch” the roll crimp and get jammed between the slug and barrel.

    I’m no expert on this, but I just recall reading about this design element ( flat ledge on outer rim on front of slug) being a good thing/ desired/ recommended for avoiding pressure issues. Just a friendly comment-not a criticism.

    Good luck. Looking forward to following your progress with this project.

  14. #14
    Boolit Grand Master


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    Quote Originally Posted by catboat View Post
    I am interested in slug loading my 12 and 20 gapump shotguns. I’ve been reading and reasearching designs and loading notes from those who have done it,

    Looking at your slug design, one thought came to mind based on my reading. I seem to recall reading that it was beneficial to have a flat ledge on the outer front rim of the slug ( sort of like the shoulder on a Keith style bullet, but with a wadcutter,minimal pronounced center meplat). Evidently ledge this allows a roll crimp to release/unroll upon firing and not create pressure spikes if the accelerating slug( that does not have a flat rim ledge, and is more “ rounded” going from meplat to slug side like your design) would “ catch” the roll crimp and get jammed between the slug and barrel.

    I’m no expert on this, but I just recall reading about this design element ( flat ledge on outer rim on front of slug) being a good thing/ desired/ recommended for avoiding pressure issues. Just a friendly comment-not a criticism.

    Good luck. Looking forward to following your progress with this project.
    It's a good question, and one I barely mentioned in my first post. The ledge does give the roll crimp something to seat on, but its usefulness is overrated. I would guess it is possible for undersized slugs to become a problem, but a full groove diameter slug can not jump over the crimp. Consider that most, if not all factory rifled slugs are essentially a round nose with no shoulder besides the beginning of the rifling. They are all roll crimped, and never once has it been a problem. In a gun with a proper throat (good handguns and rifles), I've come to be a big fan of SWC's. The shoulder's main purpose is to align the bullet in the throat, and then the bore. Down range, the shoulder will cut a clean hole in paper. That fact, along with the fact that they will generally shoot very accurately at very low velocities makes them fantastic for target shooting. They can also be driven faster than most bullet designs, and with a large meplat, make awesome hunting bullets. None of this really applies to shotgun slugs for a number of reasons. The two big ones are because a to-scale bullet in 12 gauge would be too heavy to be reasonable, think 1500+ grains. The second reason pertains to just the shoulder. Shotguns don't have throats. Without a proper throat, a SWC does not center itself as well as a round nose design. I have no doubts about that fact, but how much it will truly effect accuracy? The only way to find out is to pull the trigger.

  15. #15
    Boolit Grand Master


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    The mold is now in the Accurate Molds catalog, and I am just waiting on a reply from Hollowpoint Molds.

  16. #16
    Boolit Grand Master

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    You should be fine with the round nose. As you say, most factory slugs are round nose and without any flat shoulder.

    My first time out with 0.735" RB's I was wondering if they might run over the crimp but no problem at all. In fact I've found it a bit odd that even slugs like the Lee Drive Key wad slugs will open a roll crimp just fine... or so it seems anyway. I've had no problems with them running over crimps or petals on wad being damages which is what I expected.

    It'll be interesting to see how that slug does but I am thinking in a rifled gun it will work very well.

    Longbow

  17. #17
    Boolit Buddy finstr's Avatar
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    My knowledge of slug design is quite limited so take this idea with a grain of salt please.
    I think the slug looks great and I personally would powder coat them as its a full bore size to stop any leading of the rifled bore. I run really soft pure lead thru my .45 and .38 and so far thru my 12ga with no leading at all.
    Also the cavity in the base would be interesting if you took a page out of Lightfield's book and created a more cylindrical void with a small bump around the rim to attach an impact discarding type wad that stays with the slug during flight. Now the Lightfield wad has a protrusion that snaps into the cavity and acts like a set of vanes on an arrow to guide the slug thru its transition from supersonic to subsonic keeping it semi-stable thru the shockwave. At least that's my understanding of it. Of course we can't buy those wads but someone with a 3D printer might be able to make something like that.
    I can post pics of the Lightfield slug and wad as I have a couple here someplace
    Just a thought...
    Last edited by finstr; 04-25-2018 at 10:42 PM. Reason: pOr sPelLiN
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  18. #18
    Boolit Grand Master


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    Not a bad idea, and no need for pictures. I've shot, even reloaded Lightfield slugs. They are good, but never anything spectacular. I always had better results with brenneke slugs, with rifled or smooth bores. You can buy exactly what you describe, just look up all the Russian slugs these guys are talking about. They are various designs that go on a wad with a post. You can buy those wads, but they have to be imported from Italy (Gulandi). That design has it's own set of problems, like anything. If you could get a CONSISTENT sabot to load, I think that would be a good way to go. The problem is I have never seen one that shoots well stick around more than a year or two, especially factory ammo. I never had anything other than good enough results with any kind of wad slug. I really think a full diameter bullet is the way to go for my purposes, and I am looking for consistent sub-3" groups at 100 yards. I've tried powder coating, it's not for me. In handguns, it's more work, and I actually prefer the smell and smoke. I haven't messed much with cast in rifles, but I get zero leading in 30-30. With shotgun slugs, I didn't add any kind of lube to my last batch (Accurate 73-770S). I'm now up to about 50-60 shots, no lube at all, no cleaning the bore and leading is very minimal. Gas cutting isn't and issue, and if I heat treat these next ones, I just don't see any reason to worry. The hollow base puts the weight forward slightly, which may help with stability. I've been shooting some 770 grain plain base slugs at 1200-1300 fps, and still get 4-5" groups at 100 yards (5 shot CTC averages) which is about as good as anything.
    Last edited by megasupermagnum; 04-25-2018 at 10:58 PM.

  19. #19
    In Remembrance bikerbeans's Avatar
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    Mega,

    Did your new mold arrive?

    BB

  20. #20
    Boolit Grand Master


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    No. I ordered two molds about 3 weeks ago, and have not seen either. One for handgun coming right to my door. The slug mold is going straight to Erik, and I'm guessing he must take 3 weeks or so to do his thing. He is not doing regular pull out pins at the moment, so it will be an in-mold pin (insert bar?). Because of this, the taper will have to be increased, and I think he recommended 12 degrees. He will do a flat point pin, so that should help with weight. I also asked about a slot cut like a Lee slug, but he said it would most likely not cast well.

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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