minnie Ball casting

[barnabus]

just bought a Lyman 575213 OS mould for my 58 cal 1861 Springfield.This is my first time using a pin to make a hollow base bullet.After getting the mould and melt hot it started to drop nice looking bullets with about 30 percent rejects. i weighed the 100 that i poured once it was running and weighed each of them afterwards. The weight spread was from 489-494 grains. is this normal with minnie ball casting?

[DickelDawg]

That spread is pretty good for any bullet casting. Approx. 1% deviation.

[quail4jake]

Look for the shrink bubble in the base, notice the underweight ones show the bubble larger and often off center. 489 - 494 is right where you want to be with pure lead or 40:1. I am right now boring that mold to bring the diameter of the driving bands up to .582+ as it drops from the mold. Please let me know what diameters you're getting, I would be curious to know. Do you know the date of your mold?

[bedbugbilly]

quail4jake - for what it's worth - I have 4 575-213 molds - 2 old style and 3 new style. All of mine drop right at .575 and are a perfect for my '55 Armisport and my old Remington Zouave that I have had since the early 60's that I rebarreled with a Zoli barrel. They were a perfect fit on a 1864 Watertown (;61 pattern) that I had for many years. Fortunately I never had to size any of them for the rifles I shoot.

Grain weight variation is normal and common. The secret to casting the hollow base 575-213 is to get and keep the mold hot and get your cadence down when casting. Normally - and I ladle pour - I may get 3 or 4 without complete skirt fill when starting up, even with preheating the mold on the pot while it is heating up. Once I get going, they drop just fine.

The original barrel on my Zouave - and I have no idea who made it as it is not marked - does have a serial number and is a high quality repro - the bore was oversize and I had a friend who had a mold that would drop at .581 which worked well in it. I was going to send it in to
bobby Hout to have it re-linged to .577 but haven't done it yet. I ran across a Zoli with a birch stock that was used but not shot a whole lot. I got it super cheap and used the barrel to drop in my Zouave since the bore was in excellent shape and at .577 - I like a .002 undersize minie so the monies as they drop from my molds work just fine.

My original Lyman 575-213 - new style - I purchased with the handles in about 1964 and I have cast thousands of monies in it. The other new style I have is also a Lyman. Both of my old styles are both older Ideal blocks.

[barnabus]

Look for the shrink bubble in the base, notice the underweight ones show the bubble larger and often off center. 489 - 494 is right where you want to be with pure lead or 40:1. I am right now boring that mold to bring the diameter of the driving bands up to .582+ as it drops from the mold. Please let me know what diameters you're getting, I would be curious to know. Do you know the date of your mold?

mould date is 9-20 and drops at .578 with pure lead at 850 degrees

[quail4jake]

Great to hear input from old timers and new folks, there are only a few of us who dabble in casting expanding balls. The reason I asked about the date of your mold is that I wonder if Lyman has started making their .58 and .69 old style molds larger diameter. My .58 OS is from 2007 and drops .575 lead and 40:1, hearing that your 2020 mold is .003 larger maybe means that they're catching on. NSSA info generally calls for .001 under bore size, when I talk to seasoned NSSAers the theme I hear is tight enough that you need pressure on the rammer to send the ball down the bore and seat, which translates to .001 under bore size. If you look at NOE molds they are in the .580 - .584 range anticipating that the ball will be sized to .576 or .579 or whatever is needed, naturally if a Lyman mold drops at .575 that is a non sequiter.
Bedbugbilly, it's great to hear from someone who has been doing this so long with success. I have a Zoli zouave, 1971, and it does OK with the Lyman OS one day and falls on its face the next! The bore is just .580 so following NSSA advice I am boring the driving bands on the OS mold so that I can size to .579 in my star sizer, we'll see! Why not just buy an NOE mold at .582? Not available, so when Swede gets around to making more I probably will.
Bore size may surprise you, it did me. My Armi Sport 1842 rifled .69 pin gauges at .695! It should be .690. I just bored the mold and now the driving bands are .695 but I need more like .697 to size to .694 with my homespun star die, so back to the lathe we go...
Any ideas on how to minimize the shrink bubble? I have been at this for 45 years and still get the shrink bubble...

[barnabus]

Look for the shrink bubble in the base, notice the underweight ones show the bubble larger and often off center. 489 - 494 is right where you want to be with pure lead or 40:1. I am right now boring that mold to bring the diameter of the driving bands up to .582+ as it drops from the mold. Please let me know what diameters you're getting, I would be curious to know. Do you know the date of your mold?

i still dont understand the shrink bubble?

[mehavey]

It's the void at the bottom of the hollow base:
https://www.flickr.com/photos/155475279@N02/39202976025/

To eliminate it...
Run pure lead HOT ~780-800dgr
Do *NOT* contact pour. Instead pour about 1/4-1/2" off the hole to vent/alleviate the tendency to form an air pocket near the top of the pin.

*(Go ahead. Ask me how I know)

[quail4jake]

It's the void at the bottom of the hollow base:
https://www.flickr.com/photos/155475279@N02/39202976025/

To eliminate it...
Run pure lead HOT ~780-800dgr
Do *NOT* contact pour. Instead pour about 1/4-1/2" off the hole to vent/alleviate the tendency to form an air pocket near the top of the pin.

*(Go ahead. Ask me how I know)

I didn't have luck with hot pure lead, some of the worst shrink bubbles and very poor mold fillout. The best I've done is using 40:1 at about 650 and a mold at 450 - 480, that's about as hot as I can run a binary alloy without tin loss in dross. That seems to help but there is still a shrink bubble but less underweight throwouts and great mold fill out. The tin alloy expands and grabs the rifling but I don't know if that would work in reduced charge loads. Remember there is no history of how to cast expanding balls from the contemporary era since they were swaged, so we're all trying to figure this out!

[mehavey]

From my miss-spent N-SSA youth, I learned the requirement that pure
lead takes high (800°) heat, and that unbroken contact pour invariably
caused voids at the tip of the pin.

Thereafter, no problems:
273421

FWIW:
- Pure Lead (800°)
- 30:1 (780°)
- Lyman#2 (700°)

While higher heat in the metal does mean you have to flux more often (I use a small 'pea' of 50/50 lube) to keep
from losing the alloy mix, you do not lose that mix if you FLUX* prior to skimming
http://www.lasc.us/Kelter_Cast_Bullet_Alloys2.pdf
Meanwhile, that higher heat make your life much more simple.

See also https://thefiringline.com/forums/showpost.php?p=6617761&postcount=37

See below aso for degree of sharp fill-out when casting pure lead HOT.
273432

*"Flux" meaning melting the wax on top of the surface, then plunging the dipper/open-side down through the wax/dross/into the metal repeatedly to mix all components until only light ash remains on top.
That you can skim and discard.
No big deal.