I purchased a new Lyman Foster Slug mould and ti ...............

[prs]

.......... cast non-rifled Foster slugs almost perfectly. I was using pure lead at 770F bottom pouring using pressure pour technique with pre-heated mold that had been scrubbed with Dawn Platinum and hot water, then rinsed. Just my SOP. Very first slug fell out perfectly cast and out or 200+ cast only two rejects from where my spout had a cool bead of dripped lead that partly clogged the spru plate. No trouble with the center plug or loose screws or anything. Maybe Lyman is getting their act together, should I go buy a lotto ticket?

Of course, there is one glaring flaw in their design, the slug's outer diameter is way small for 12ga bore size. But, it is specified as that too small diameter. Due to that, this particular design is infamous for being inaccurate, but I am going to work with it a bit to see I have better luck.

prs

[tomme boy]

Send it to Eric at Hollowpointmolds and have him open it to whatever you want.

[GBertolet]

I have that mold. It was casting at .705 using pure lead. I opened mine up to .730, on a lathe with a boring bar. Looks like a giant belt along the side of the slug now. I still had trouble getting the slug to shoot well. Recovered slugs show the skirt is collapsing from the setback of firing, causing fliers. I may have to make a smaller plug to make the skirt walls thicker, or go to a harder alloy. Anyhow I am having such good success with the .735 RB for hunting, the Lyman mold project has been defered to another time.

[longbow]

I have heard of a wide range of as cast sizes from 0.685" to 0.705" for the Lyman Foster slugs. My mould casts 0.705" with soft lead.

I believe the reason the mould casts undersize is that Lyman (Ideal?) used to sell a swaging tool to put rifling on the smooth slug. If 0.10" grooves were swaged into teh slug that would raise 0.010" lands/ribs which would take that 0.705" slug and turn it into a 0.725" rifled slug. Speculation on my part as I do not have a rifling swage. I have seen them and almost bought one but decided I didn't like the overall thin design of the Lyman slug anyway.

Personally I think Lee has a better idea with the Drive Key slug and my first time out with the drive key slugs I got better groups than I got after much load testing using the Lyman slug.

Yes, the Lyman Foster slug has too thin a skirt... and nose. It is in my opinion a poor design and I am surprised they have not improved it. They did design the Lyman sabot slug which is a big improvement but also a different type of slug. It would be nice to be able to buy a commercial Foster mould of a good design like turbo1889's design.

I do like Lyman iron moulds but I wouldn't waste my time with the Lyman slug anymore. Best to get the mould machined to bore diameter as stated above.

My thoughts anyway.

Longbow

[prs]

All of the above thoughts are appreciated. After giving this a good try, I may well have it machined to true 12 bore. So far, I have only shot one test group. Four of the shots fomed a group of about 9" at 75 yards, but one of the five flew to some where beyond my 40" backer board! This was one of Lyman's publshed recipes with Unique, the charge reduced by 20% and Teflon wrap between slug and hull wall. The loading goes S-L-O-W with the gas seal and wads and Teflon wrap (which has to be cut into more narrow strips to fit the slug without getting pinched by the roll crimp). So I may get tired of this pretty quick. This is not for hunting, just family "Slug Fest" fun shoots. I may stick with my 7/8oz Lee for quick reloading of lots of rounds.

prs

[longbow]

My conclusion as well. Wad slugs (those that are sized to fit into shotcups) are much quicker and easier to load.

I do have to say that 9" at 75 yards is nothing to sneeze at especially with the Lyman Foster. I found myself lucky to get 8" at 50 yards with any regularity at all using Lyman load recipes.

Paper patching to bore helped and something like Teflon wrap, mylar wrap or similar to bring the slug up to bore diameter should also work but it introduces another item into the reloading and a variable in that how it is added and whether it is affected by opening crimp, jumkp through the forcing cone, etc. all play a part in accuracy and consistency.

There are a couple of alternatives to bring the slug up to bore size:

- wrapping with paper or...?
- machining the mould to create a bore diameter slug
- swaging or "knurling" the slug up to bore diameter


In the end I still think that the Lyman Foster slug is a less than optimal design so I have not pursued it further.

I think you will find easier loading and decent accuracy with the Lee 7/8 oz. slug. It has a good reputation from both smoothbore and rifled guns. I have the 1 oz. Lee mould but not the 7/8 oz. which I keep threatening to buy but haven't yet. I think it would be a good mould to have though.

Longbow

[Grmps]

Throw a few layers of PC on them and see if they fair better

[longbow]

0.020" of PC would be a lot! These aren't just slightly small, they are stupidly small. Not sure what Lyman was thinking but it would be closer to size them down to fit a wad than PC them up to fit the bore.

I guess if you can put several thou a coat on then PC might work but it seems like a lot to me.

[Hardcast416taylor]

I have heard time and again that those rifling grooves on Foster style slugs are only there for cosmetic looks to impart the idea that the slug will develop rifling rotation in its travel in the barrel. In short, in a smooth slug barrel it flies like a thrown rock. The addition of a rifled choke tube (Remington slugster tube) will impart some rotation to slightly improve accuracy. As an old gunsmith once told me about Remington 1 oz. lead slugs, `If you listen carefully you will hear them rattling against the sides of the barrel while going down it`! Through my years working for a shop sighting in any firearms that needed sighting in I found that Winchester 1 oz. Foster slugs were much more accurate than the other brands of Fosters in either a smooth barrel or with some manner of rifling.Robert

[longbow]

I think a bit more than cosmetic in that I believe the swaging operation enlarged the outside diameter of the slug and if so then it would be a closer fit to bore. SluggerDoug did that using helical gears to "rifle" the slugs which brought them up to bore diameter. If the slug is closer to bore diameter it has a fighting chance of improved accuracy.

You are absolutely right though that the rifling has little to no effect on producing spin on the slug.

Even Brenneke claims their deep helical ribs do not produce any spin stabilization.

Having said that there are some internet slo mo videos of ribbed/finned/rifled shotgun slugs that do pick up a spin but ever so slightly and certainly not enough to produce any sort of stabilization. I would not have thought that any spin at all would be produced due mostly to shock wave and turbulence interfering with air flow but there you go, wrong again.

Soft slugs do bump up as I found with my Lyman Fosters cast from pure lead and shot into soft snow. They start out at 0.705" and wind up at bore diameter but the skirts and noses of all recovered slugs were a different shape and not from impact, from uneven obturation and/or cocking through the forcing cone. Why Lyman and the factories make them so undersize is beyond me especially when they do bump up so are bore diameter if they hit a choke. Why bother, just start them out at the right diameter.

Longbow