Finned 12ga slugs

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Freyr_255

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So in my pursuit of finding Brenneke slugs in Canada I looked into making my own. Good luck finding a mold(seriously though they aren't that difficult to make..I just don't have the tools to do it). I still cannot figure out why no one produces a mold for these. So digging around the internet some more I stumbled across these cute little things.

finslugs.jpg



And this got the wheels turning. So I started playing with designs and came up with some cool ones, but only this one turned out IMHO to be practical. KISS principle and can be done in a 2 piece mold. The fins would have to be cut with a slight taper into the body as well to facilitate mold release, and possibly the bottom as well. One I drew up that has cut outs in the fins to increase drag looks like a little bomb. It's extremely cute, but I figured the drag increase wasn't likely to help much and making the cut outs would just complicate things.

FinnedSlug.jpg



With my renewed interest in tracking down Brenneke slugs I figured I would ask around for people's opinions on this design. I've sent it in with some dimensional numbers I crunched to be roughly 1.25oz in weight to a custom mold manufacturer to see if he can do it. I'm a little up in the air though as I'm not sure who would be tooled to do this kind of a design as I assume most custom mold guys are doing these on a lathe and likely not able to make the fins.

As a side note I gave it dimensions similar to a Lyman 425gr sabot slug so that it can be loaded in cup wads with a fold crimp. Reasoning is I want this design as a hard cast bear slug at short range so I don't need to get fancy with the tolerances and I want it to work in many different guns without causing damage. Rational for kick ass design: cause I can. Plus if I want Brennekes in this country it seems I would need a custom mold anyway so I might as well go big. I'm hoping I can get this design made and it works well because I think it would be a massive improvement in shotgun slugs that is about 50 years overdue.

Afterthought: Cute bomb 'higher drag' design. It's cool but I don't think practical to produce a mold for. It may also have issues with fins deforming on firing with the cut out.

Slugdesign8.png
 
Ballistic products or Precision reloading sold/sell a plastic set of fins that you put on a 12 ga. round ball and amounts to the same thing as what you're doin', I've never tried it because I think the Lyman "sabot" slug does much the same. Bp and PR sell all kinds of this stuff for slug and shot shell tinkerers.
 
Suggest you might want to put a slight cant on the fins. Fin-stabilized armour-piercing projectiles have that, not for gyroscopic stability but rather to cancel out any irregularities. The projectile flies, in effect, a spiral path, but that's better than it drifting off to one side or the other.
 
ATOM said:
Suggest you might want to put a slight cant on the fins. Fin-stabilized armour-piercing projectiles have that, not for gyroscopic stability but rather to cancel out any irregularities. The projectile flies, in effect, a spiral path, but that's better than it drifting off to one side or the other.
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Good idea. I might have to modify that in.

So apparently that guy I contacted can't do these(cnc lathe bore only..). Anyone know of someone with a cnc mill that does bullet molds? I found one guy that says he has cnc mill capabilities but he's not taking orders due to health reasons.

The problem I have with all the slug designs out there right now is they are rather limited in what they have to offer. Ya a giant wadcutter pellet is cool. No I don't want that profile. Same goes for the little half dome fosters(why are these popular??). Brenneke slugs are more or less what I'm after in design but ya...attaching a wad accurately is not easy without a 3 part mold to give a pilot hole. I might go this route but I want to try and upgrade shotgun slugs a bit since people's take on them is "it should be massive and not aerodynamic and any sense of the word". Honestly the design is not complex...one just can't pop them out as easy as slapping 2 blocks against a cherry cutter...

Going to modify fins and put up another pic.
 
I am no machinist...but a reloader. My Lyman chamfer/deburr tool is machined by the looks of it on a milling machine (if I remember gr 10 shop). The chamfer side may have a close resemblance to the fins on your slug, it may help, it may not.

Link is just to provide picture of tool. w ww.optics planet.net/lyman-extra-large-caliber-deburring-tool-7810206.html
 
So angled fins are a terrible idea for keeping it simple. Going to abandon that design.

Trying MP-molds.com to see if they will make one. I'm skeptical as even though they have a cnc mill their site isn't exactly non-commercial orders oriented. Actually crap I just noticed in their FAQ section they have minimum order quantities...so scrap that idea.
 
A thought. Is there a tech school near you, one that teaches tool and die makers? The teacher might be willing to take on making a mould as a project for his students.

Failing that, there are lots of companies making moulds; you don't necessarily have to go to one specializing in bullet moulds. Think of every cast object you've seen - every one of them came from a mould somebody made. It's not an impossible task, by any means; it all hinges on what you are willing to pay for it. Casting lead is not that high-tech; it's been done for thousands of years.

One other thing to consider is the actual loading process - how to keep the slugs straight and ensure obturation.

BTW, have you a link to the site with the original photo you posted?
 
Ya there is just the Yukon College really and I don't think they have the capacity. I'm actually almost thinking I might try making them in a silicone mould. You can get the higher temp stuff for casting lead and zinc so it should work out. Only downside is that its softer/mailable as a mould(plus then I can make all sorts of cool stuff :p ). And a good point that it might be easier to find someone to make a mould that doesn't do bullet moulds. Only downside is then I have to give whole block specifications for handles and crap. Not difficult just one more step.

The guys who make the dies for the first ones are Corbin. They make a bunch of swagging gear. Click on the picture with a whole suite of slugs displayed and that one I posted comes up.
ww.corbins.com/slugs.htm
 
ATOM said:
Now that is very cool. Thanks for the link.
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Agreed. Also very expensive. :p

I'm going to try and make some Brenneke slugs here at some point and put the finned slugs on the back burner unless one of the companies I e-mailed gets back to me with a positive response. Since I just picked up a drill press today(General has a sale on...I couldn't pass up a General International for the same price as generic crap :p ) which will allow me to make a less than production friendly 3-part Brenneke mold. Also that damned 11/16 bit cost $36 so it had better damned well work out. I'm hoping I don't take too much metal off with it as the bit is 0.685-0.690...which is about what I want...thinking it might end up at .710 which can work with no cup and just wadding. Other alternative is to use a 5/8 bit which is 0.630 or some such and ream it out. Not exactly ideal.

Now to find some metal in which to make this.....I miss having a scrap pile/metal rack laying around.
 
You could try something like boring a hole through a block of brass (by preference) that has your nose shape just poking through, then have a base plug with the fins cut in. Do a nose pour, pop the plug out the bottom and there's your slug.

J
 
achtanelion said:
You could try something like boring a hole through a block of brass (by preference) that has your nose shape just poking through, then have a base plug with the fins cut in. Do a nose pour, pop the plug out the bottom and there's your slug.

J
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Very good idea. This is actually how I was going to do the Brenneke mold more or less. The only hard part of this will be carving the plug with the fins in it to fit the hole perfectly and be uniform as I don't have much for tools to work with. That being said I should be able to pull this off if I can find the right materials as a starting point.

Really this will probably end up being mild steel though as brass and aluminum blocks/rods are in short supply around here. Might upgrade at some point though.

Lee has gotten back to me with a positive response. They want to see a drawing so I'm drawing up some scale ones right now to submit to them(you know...cause I don't have AutoCAD kicking around...). I'm thinking I should almost re-design this slug to jut be full bore and loaded with felt wads rather than a sabot in a cup. It just seems a bit short on the fin side(0.450") to me for some reason, but I'm at my maximum length(0.780") which duplicates the Lyman sabot slug. Really my main problem here is I don't know how much I can push slug dimensions so I'm just kinda copying what is already out there....which is bloody limited. I guess if I went with full bore dimensions then I can just have whatever length as it will be made up with wad and roll crimped. This wanting to have a sabot slug makes life more difficult dimensions-wise.

Does anyone have various cups to measure depth of for me for both 2 3/4 and 3" so I know what my limitations are? I'm still getting into shot shell reloading for this express purpose...don't have much kicking around to measure/play with.

I'm going to submit this drawing to them anyway just to see if they can do it, I might just hold off asking for production while I tweak the design.

I'll post the drawings I submit as well that are more or less scale(1"=10cm...its a great scale). And really I did all my measurements in the drawings in inches just because they have nice round numbers for bullets and most tooling is in inches.

Also design inputs are greatly appreciated. I've got a basic design down but really if people have suggestions I'm more than open to them. If I get Lee to do this I may just order 30 molds because then they don't charge for tooling set up etc. I really can't see any reason why this slug wouldn't fly straight and I'm sure some people would be interested in playing with a new slug design. Let's face it...if a foster slug flies straight, these should be like an arrow by comparison.

*edit*

Finished the sketch.

Sketch.jpg


*edit 2*

Additional thought on producing a mold as described above with a rod in the bottom. Fins in this respect wouldn't be terribly difficult to produce. If one took a rod and drilled a hole dead centre in it, followed by creating an X pattern with a saw through the rod(or 3 cuts for a hex), it would produce much the same thing. I also just realized the taper I put on the fins is not actually needed for mould release purposes as there is nothing for the cooling lead to pinch like on square cut lube grooves(*afterthought facepalm*).

The hard part of this design then becomes alignment of the cuts. Both perfectly centred drilling and cross cuts. I think I could pull off the centre drilling given my equipment but the cross cuts are another matter. I have tried to split bars before and it takes something extra to do it evenly enough not to throw off ballistics. Thinking metal band saw and fence. Neither of which I have. That being said second cut on this set up could get tricky to keep it aligned perfectly with the first cut. Given a decent machine shop this should be cake to produce however.
 
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I tossed my textbooks on this years ago, but am pretty certain that your fins are so close to the main body that they are going to be mainly in a vortex zone and will be unable to exert much beyond the most minimal effect on stability until the projectile has a major yaw. The likely result would be at best a yaw-driven zig-zag path in the general direction of aim. My suggestion would be to find some way to lengthen them.

As well, I would reiterate my early suggestion about a slight cant on the fins. The canted ribs on Foster slugs do not spin them anywhere near fast enough for gyroscopic stability to kick in, but they do provide a slight spin, enough to cancel out any other deformities. If a given slug is likely to drift to the right, for instance, this keeps it spiralling around the trajectory it would have had without the spin.

This is very interesting looking over your shoulder. Thanks for letting us kibitz.
 
ATOM said:
I tossed my textbooks on this years ago, but am pretty certain that your fins are so close to the main body that they are going to be mainly in a vortex zone and will be unable to exert much beyond the most minimal effect on stability until the projectile has a major yaw. The likely result would be at best a yaw-driven zig-zag path in the general direction of aim. My suggestion would be to find some way to lengthen them.
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Ya....this was kinda why I was worried but talked myself into ignoring that detail for the moment. What I can do easily enough is trim the cone on the base down to a cylinder that just removes the sharp edge from the meeting of the fins, shorten the band behind the nose taper, and add all this additional material to the fins to lengthen them. The main concern is I don't have enough shotshell reloading experience to know what the maximum allowable length of a slug is as wad thickness/type affects the load drastically.

My other thought is to rip off a design I saw on Corbin's site and make a slug that looks like my base drawing only. Maybe a larger cylinder in the centre. Kinda almost a sabot round minus the plastic sabot holding the smaller projectile. Talk about 'star power'. :p
 
If you are talking about fin or flare stabilization, I think that your limiting length is going to be what you can fit in a shotgun hull. Think of an arrow; there's no max length. Your simplest solution might be to hunt around and find the longest shot cup available. Although I gave up shotshell reloading years ago, I think I remember seeing photos of ones designed for steel shot that had virtually no compression and were thus longer.
 
ATOM said:
If you are talking about fin or flare stabilization, I think that your limiting length is going to be what you can fit in a shotgun hull. Think of an arrow; there's no max length. Your simplest solution might be to hunt around and find the longest shot cup available. Although I gave up shotshell reloading years ago, I think I remember seeing photos of ones designed for steel shot that had virtually no compression and were thus longer.
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Sounds like a plan. I'll browse around for steel shot cups.

*edit*

Rough profile for the 'lead sabot' round based off quick scale drawings I made on paper. More or less same thing with a different center profile...from diamond/tear drop to cylinder. I would imagine this in a rifled barrel would fly almost like a bullet. Fins could be adjusted off 90 degrees to impart spin in the air easier as well.

leadsabotprofile.png
 
ATOM said:
My bad - I should have mentioned weight as well. No doubt you thought of that already, but can't be too careful.
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Ya weight is in consideration. I go for outer dimensions and then adjust things like that solid band and fin thickness to get the right weight. Really leaving certain dimensions fluid allows one to get exact weight easily enough. Hardest part is not going over my 1.25oz limit. I could push 1.5 but load data would be a #### to figure out more than it already will be...also the reason I was trying to do a standard weight in a shot cup; Easy load calculations.

Any thoughts on the 'lead sabot' profile? I'm thinking it might almost be the better way to go. You will still get a hole the same diameter as a full size slug, more torn than punched from the fins causing some rather serious trauma. Should also penetrate well if one lengthened the nose cone a bit. If it hit a shoulder blade it might punch and shear the fins but I dunno. Either way that one was drawn with a .40 cal core which will do some damage either way.


*edit*

Browsing the net a bit I came across some pictures of the lyman 525gr slug in wads. Looks like I can easily lengthen mine as they were blocking them up with felt wads to get the proper height in the wad cup. Still no dimensions found though for cup depth on magnum wads.
 
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