Modified Forsther Slug

[missionary5155]

Good morning
While working on my Matchlock lock cutting parts I began wondering what if the standard mold had the hollow base plug modified so the cavity was not so deep? What if it was just half way or even just a third along the lines of the skirt on a mini ?
Then it would have a more solid head and have to penetrate much better. Would also have an increase in mass so again better penetration on hard resistant items.
But in the end still would not match a solid RB in any way... Oh well back to hacksawing parts for the Matchlock.
Mike in Peru

[GabbyM]

20 gage with a solid slug down a rifle barrel is hard to beat.
Would be easier and cheaper to have a custom mold made to simulate the .577 Minie sans hollow base than develop a new gun. Make the slug fit grove diameter. Lube it then load over fiber wads.

I just use a muzzle loader here in our state of Illinois.

If you made a pump action dedicated Minie ball shooter it would be a rifle and not a shotgun. Thus would not meet Illinois deer hunting regs. IMHO. However if it was a one of a kind wildcat whose shells were 1/8” shorter than a standard 20 gage. Who would notice. Call it the 20 outlaw. Not really my cup of tea. Would make a good episode for one of those silly TV shows. They’d have to fit the round into a Saiga auto loader of course.

[turbo1889]

Yes, making the hollow base plug shorter and getting a thicker tougher nose on a hollow base foster slug as a result produces noticeable results in the terminal effect on game. This is especially true with hollow base foster slugs cast from pure or nearly pure soft lead.

I have two interchangeable hollow base pins for a custom full-bore 12ga. slug mold I have. One produces a hollow base that is 2/3 of the slugs length deep and the other produces a hollow base that is 1/2 of the slugs length deep. The difference in penetration vs. expansion is incredible with slugs cast from soft alloy and fired from a smooth bore gun. The slugs with the thinner nose and deeper hollow base just about turn themselves inside out on impact and make big silver dollar shaped hunks of lead that only penetrate about 2-3 inches deep when fired into the end-grain of big Dug-Fir firewood rounds and tear a big round "blast cavity" at the impact point. Where as the slugs with the thicker nose with the hollow base that is only 1/2 of the slugs length deep cast from the same soft nearly pure lead fired from the same gun with the same powder charge penetrate over twice as deep and tear a longer narrower channel in the wood test medium and the nose of the slug "mushrooms" instead of the whole slug turning itself inside out and flattening out into a big flat disk. The difference in weight between the two is just barely 1/8 of an ounce with the slug with the deeper hollow base weighing in at just a smidgen under 1-1/4oz. when cast from soft lead and the slug with shorter hollow base plug and thicker nose weighing in at just a smidgen under 1-3/8oz. when cast from soft lead.

On actual game the 2/3 deep hollow base, thin nosed 1-1/4oz. slugs of soft lead fired from a smooth bore shotgun at 1,300-1,400fps. muzzle velocity leave a massive exit hole on deer that he can stick your fist through and work great for maximum terminal performance on such light boned, thin skinned, medium weight game but I do not and would not trust them for effective penetration on heavier boned, thicker skinned, heavy weight game, especially dangerous game at least when cast from soft alloy. The 1/2 deep hollow base, thick nosed 1-3/8oz. slugs of soft lead fired from a smooth bore shotgun at 1,300-1,350fps. muzzle velocity leave about a 2-3" diameter exit hole on deer expanding minimally. I have yet to actually try them on heavier or dangerous game but I would be much more comfortable with them for that purpose if I had to use a hollow base slug in a smooth bore gun, especially a soft lead one which is necessary with a choked gun if the slug is full bore diameter without some kind of narrow horizontal ribs like a Brenneke (actual brand name not just type) slug or similar which can still be choke safe even though they are made of rather hard 4-5% antimony swagging alloy due to having narrow horizontal ribbing (more commonly inaccurately refereed to as rifling) which allows the slugs outside diameter to squeeze down in the choke without putting excessive stresses on the choke which could damage it.

[missionary5155]

Howdy Turbo1889
Thanks for posting all that info. Had a feeling it would have to be far better than the origonal configuration. A two inch exit hole on a corn cruncher that went through the chest is massive. I would not dought it would destroy a shoulder and anything else in the way.
Thankds again.. that was an interesting read.
Mike in Peru

[turbo1889]

Yup, currently my main line of thinking for hollow base slugs includes making the hollow base about half the slugs length deep. Which makes a thicker nose then a conventionally proportioned foster slug and as a result its a little heavier. Makes a huge difference in terminal impact behavior with soft lead slugs (not as much difference with hard lead) and I think it also improves the slugs balance at least for a smooth bore slug design putting a little more weight in the nose of the slug and moving the center of balance a little further forward then the standard design. I also prefer a shallow angled "bull nose" TC shape up front rather then the conventional round nose shape.

Here is what I'm talking about:
http://farm9.staticflickr.com/8403/8604283341_63c1603bdc.jpg

Conventional Foster slug proportions on the left, how I like to set-up mine on the right. That is all to scale since it was a screen capture out of CAD.

[longbow]

Mike:

One of my failed experiments was to make a Foster mould with an RNFP design with large meplat, thick nose and a long thin skirt. The idea was as you say, to make a slug with a heavy thick nose but also to have a thin light skirt then fill the hollow base with hot melt glue to support it so the nose is the "projectile" and has most of the mass and the skirt is just to keep things nose forward. I bored the mould at 0.685" to suit standard wads.

For whatever reason I have as yet to figure out it did not shoot well at all. I did not recover any slugs though so don't know the reason. Fit to bore was good and the logic was sound (I think so anyway but I may have a few screws loose) but in fact I failed again!

I had figured the skirt was so thin that it wouldn't fill out well but they cast very nicely. I suspect the skirts may have bulged or split even though they were a tight fit to bore. Now my Brennekes using only hot melt glue "skirt" and solid nose are working pretty well. Go figure!

My next trial will be similar to turbo's TC slug but thicker shorter skirt then filled with hot melt glue and extended as an attached wad Brenneke style and sized to fit into a shotcup. The cavity should provide enough surface area for the glue so I don't need to run a screw into the slug as I do now to hold the skirt.

Now would that be suitable in your matchlock... not likely but I got to rambling.

What you might look up is information on the "Nessler Ball". I was going to make a mould based on the images I have found but it turns out that the Lee Drive Key slug appears to be very similar proportions so I strongly doubt there would be any significant difference in performance. However, do look up the Nessler Ball and you will see some pretty impressive claims of range and accuracy.

However, I am with you on the round ball comment! Still having trouble beating the god 'ol simple round ball for most shooting.

Longbow

[turbo1889]

A quick note on the thickness of the skirt walls on foster slugs. I found that for a 12ga. (0.73" diameter) slug one can't go much larger then 0.50" diameter on the hollow base to keep the skirt walls thick enough to sustain the loads of firing. That was with lube grooves in the sides of the slug so that on the bottom lube groove the thickness of the skirt wall in the bottom of the lube groove was about 0.09". I wouldn't make your skirt walls any thinner then that at any point if you want it to hold up structurally.

As you may have noticed in the CAD screen shot I posted above the skirt walls on my type of slug are thicker then the normal foster slug.

[longbow]

turbo:

I remember your post on the custom hollow base slugs/moulds (Brooks mould?). How did they do for accuracy in the end? Especially the shorter hollow base version.

Just wondering how far you had shot them and what sort of accuracy you got.

As far as I recall you were not shooting very long range when you posted after getting the moulds.

I am still searching for the elusive 4" group at 100 yards that Lyman claims their Foster will produce (I am doubting Lyman's claim). I have gotten 6" +/- a bit at 100 yards with some slugs but those are the exception.

Longbow

[turbo1889]

turbo:

I remember your post on the custom hollow base slugs/moulds (Brooks mould?). How did they do for accuracy in the end? Especially the shorter hollow base version.

Just wondering how far you had shot them and what sort of accuracy you got.

As far as I recall you were not shooting very long range when you posted after getting the moulds.

I am still searching for the elusive 4" group at 100 yards that Lyman claims their Foster will produce (I am doubting Lyman's claim). I have gotten 6" +/- a bit at 100 yards with some slugs but those are the exception.

Longbow


It's not just the slugs from my Brooks mold. I've done testing with a lot of other hollow base foster slugs as well, some of the conventional arrangement and some at or more towards how I like to set them up. Problem I have for comparison with your numbers is that I rarely test smooth bore loads out to the 100 yard mark. Yes, it is true that the initual information I posted about the Brooks mold were test shots mainly to test terminal effect more then accuracy at very short ranges but I have tested them further out then that. I usually test my smooth bore loads for accuracy at the 50 and 75 mark. For a smooth bore slug gun I consider the 50 mark to be normal range and the 75 mark to be long range, I just have never had much expectations of getting usable results much beyond the 75 mark with a smooth bore. Yah, every once in a while I've tested an exceptionally accurate load out to the 100 yard mark but that has not been normal operating procedure for me. If I want to shoot in the 100+ range I use a dedicated rifled barrel slug gun and even then even my very best loads out of my very best gun haven't been able to push out much beyond the 200 yard mark with even a solid slug design which does not have the inherent problems of hollow base slug design.

Since round ball loads are the accuracy standard you are most familiar with I can tell you that with the right load out of a smooth bore I have been able to slightly better the accuracy of the round ball loads on the margin with my improved hollow base foster slug designs which use a TC nose shape with thicker skirt walls and a hollow base that is only half the slugs length deep making for a thicker nose. Basically I can pull the same size core group as the round ball loads while reducing the number of fliers around the core group. For example at the 75 mark using 0.735" RB loads out of my Win-1200 sawed off pump shotgun with custom ghost ring sights if I do my part shooting off of sandbags on the bench I can print about 4" groups with the occasional flier (about 1 in 5 to 6 ) that opens up the group to more then 6". Using the same gun at the same 75 mark using loads made from my Brooks mold with the shorter pin installed that makes a shallower hollow base and thicker nose I can match that 4" group but at the same time I can bring the fliers that open the group up down to only about 1 in 20 or less.

That's all out of a smooth bore of course, with a rifled barrel slug gun the round balls usually show a substantial drop in the number of fliers that open up the group and the "core group" also tightens up quite a bit especially further out then the 50 mark. Where as when shooting hollow base slugs out of a rifled barrel slug gun the percentage of fliers does not go down and the "core group" tightens up only marginally.

It isn't so much for any improvement in accuracy that I would choose a hollow base foster slug designed my way over a round ball. But rather for the difference in terminal effect. With a round ball your only option to adjust the terminal effect is to adjust the alloy it is cast from. With a hollow base foster slug you can make changes to the nose shape (mainly adjusting the size of the flat on the nose and the angle of the nose for my TC nose shapes) to produce terminal effects substantially different from the terminal effects of a round ball regardless of how much you vary the alloy.

In Conclusion, my point is that you can make a hollow base foster slug that will shoot quite well out of a smooth bore shotgun. The way to accomplish this, however, is not with the conventional round-nosed, thin skirt, deep hollow base, and thin nose foster slug design. Some changes to the design need to be made to get it to shoot acceptably. I make no claims that my design is the best design or even that a totally different type of slug design other then a hollow base foster slug isn't potentially more accurate. I'm just saying if you want to make a foster slug perform these are some of the changes that will help in that direction. Basically, if you want to shoot a foster slug then here is one way to do it and actually get some decent results because the stock molds along the conventional design parameters will only frustrate you.

First ~ Fix the outside diameter, most foster slug molds are undersize, that is the biggest problem.

Second ~ Fix the diameter and length of the hollow base pin, most foster slug designs have too large of a hollow base diameter that is too deep. This makes a weak thin walled skirt that can't hold up structurally and a hollow base that is too deep doesn't make the nose heavy enough to balance the slug properly for best shuttle-cock effect out of a smooth bore.

Third ~ Fix the nose shape, a 1R profile round nose only has good accuracy at sub-sonic velocities. If your loads are supersonic almost any nose shape other then a 1R profile round nose will have better accuracy. Personally I find a short squatty angled TC nose shape with a large but not too large flat on the nose to be ideal. Others have had good luck with other nose shapes including nearly full wad-cutter nose shapes with just a small angle or curve around the edges and also curved radius noses just with a 2R or higher profile with a good sized flat on the nose and even sharp pointed noses with only a very small flat at the tip just large enough for a pore hole.

[missionary5155]

Good evening and thanks Turbo.
I had no idea the nose shape is such a factor.
Did the thicker skirt modification to a caliber .58 Lyman mini as I wanted to shoot a 40-1 faster than with the 60 grains. My targets were showing a hole much larger than .58 and recovered slugs showed base flare to near .80. Seemed to help up to 80 grains of 2F. But then I also discoved my Zouave has a 1-66 twist and shoots a RB so much better.
Thanks a bunch for that welll written explanation.
Mike in Peru

[longbow]

Thanks for that turbo. Good info!

Maybe I am dreaming thinking about 100 yard smoothbore accuracy. Mostly I shoot at 50 yards as well and as you know, round balls do quite well to at least 50 yards.

my undersize TC hollow base mould is similar to yours though it was originally designed to be a solid loaded into thick steel shot wads for rifled barrel. The original was a solid HP design by Greg Sappington bbut it got some more development so used the mould to make a TC hollow base slug then patched them up to snug fit to bore in regular shotcups.

I made two versions ~ TC and full wadcutter. Neither shot well until i oven heat treated and they had quite thick skirts. After oven heat treating the TC slugs shot quite well at 50 yards and equaled of maybe bettered round ball groups by a bit running pretty consistent 3" five shot groups. I didn't stretch the range out though to see how they held up at longer range. Not sure why, I just didn't. partly I didn't want to oven heat treat and partly I didn't like the extra work patching so put them aside.

The full wadcutter slugs did not work well for me.

The TC design is quite similar to your TC design but with slightly less lead in the nose and a little deeper cavity.

I plan to cast some more up and give them a go at longer range but maybe 75 yards is more reasonable. I am also planning to modify the mould some to bring the nose diameter up to 0.675" with a driving band then use an attached wad of slightly smaller diameter to suit the tapered petals in the shotcups ~ around 0.665". I will probably open the body up full length to 0.665" then have the slightly larger nose driving band and that way they can be hollow base or attached wad slugs. I do like versatility!

I had some full bore Rapine slugs in a TC design that I liked and they shot pretty well too, so that was the nose shape I copied for mould. They do shoot pretty well and they make nice clean hole in paper. They penetrate well in wood too. A thicker nose like yours would only improve that.

So far I am finding that while I like full bore slugs, I tend to get better results and easier loading using shotcups in my smoothbores. I think if I was using a rifled gun I would be using full bore slugs though.

Thanks again for all the info.

Longbow