Casting question for my 38-40 bullets

[KirkD]

Gents, today I cast some 38-40 bullets with my RCBS mould. It is only the second time I've casted, so I'm still learning. Two questions:

1. For some of my bullets, the sprue broke, taking a little piece of the base of the bullet with it where it attaches. For other bullets, the cutter cut it nicely. Does the breakage occur because I waited too long, or did not wait long enough, before cutting the sprue?

2. It was dogonned hard to get the plain base bullets to completely fill out around the very edge of the base. Many of my bullets have a slightly rounded edge all around the base. What's the secret to having sharp edged plain bases?

[mooman76]

The sprue broke off a little piece of lead because the lead was still a little soft. It happns a little more common after you throw some bullets and your mould get up to temp more. You could either turn the heat down a little if it's taking too long to cool or weight another second or 2 before cutting with the sprue. If it is a little tiny piece and in the center I wouldn't sweat it too much.
It is hard to get the corners to fill out real sharp. Adding a little tin helps sometimes or turn the heat of the mould up a little more. I don't sweat it too much as long as the corners are filled out evenly and mostly filled out but nice sharp corners are certainly desireable.

[missionary5155]

Greetings KirkD Moonman76 said it well. I have been casting for a 44-40 (a 38-40 but fatter) for some years now... The base is key to gas sealing so the better they are the better seal you get. Is your Boolit of large enough diameter to fill the chamber ? My chamber is well worn (.434) so I cast to fit that.. not the muzzle which is nearer .431. A lead boolit easilt "swages" down as it passes through the barrel. Also I do recommend you use the softest mix possible ... PURE WW will cast larger than PURE Lead.... (One way to get Fatter boolits) but a soft boolit will respond much better to the barrel and of course at the lower velocities really expand. But again FILLING the chamber end is MOST important.
Black powder will help bump up the boolit base if that is needed. My 1892 winny really likes Unique (8-10 grains). Your case is really the same only necked down about .030 so no real difference. I have a Winny 38-40 up in Illinois that I treat just like my 44-40 down here.... Just a lighter boolit. These are GREAT old chamberings and SUPER to shoot and pop rocks with. ENJOY IT !!!
My old Winchester mold requires the mold to be HOT to fill out the bases real good. My Rapine mold (aluminum) does it much better but it still needs to stay hot at the sprue plate.
You did not say how you cast... but be sure there is a good puddle on top of the plate.. I use a dipper and some molds require a Good supply of lead in the dipper and complete and sustained closer between mold and dipper while the mold fills. The full dipper adds preasure to the lead flow to help fill out the mold. Many molds are different "individuals" and ya have to play with them. When you find out "what works well" write that down for the future as memory sometimes get cluttered...

[crabo]

I have opened up the sprue plate on several molds, with a 90 degree countersink and it helps the bases fill out much better. It gives you a bigger funnel to make a better sprue and a little larger hole to pour the lead in.

I also use the Bruce B speed casting method of touching the sprue plate to a wet towel, once it turns frosty. Really speeds up your casting. Go to Castpics and read the article.

[KirkD]

Thanks, fellows, for that helpful advice. Crabo, opening up the sprue plate holes makes sense to me. I was thinking that myself this afternoon ... 'why are those holes so small?' I wondered. I was using used wheelweights. My first casting session I made 500 grain bullets for my 45-70. Things went easier, but I figure it is because 1,000 grains of hot lead in the double cavity mould kept that mould nice and hot. This RCBS 38-40 mould was a double cavity mould, but those little boolits were a lot smaller .... 180 grains each, so the mould took longer to heat up.

I have to say, fellows, I sure like all the money I save by casting my own out of used wheelweights from the local garages. I'm really looking forward to trying out my old Winchester 1892 38-40 (made in 1913, with a very nice bore). I bought it last spring, but was waiting until I could cast my own bullets so that I could load my own cartridges.

[freedom475]

If you are using a bottom pore pot:...if you place the mould tight against the spout and fill you will get good base fillout. Just be sure to hold the mould to the spout, with the spout open, a few seconds after you think the mould is full. This presure increase will fill out your bases.

If you are using WW and you let some zinc ones into the mix, this seems to make the spures break off as well as when the mould gets too hot.

Hope this helps

[August]

When I first started casting, I was amazed at how long it took for a cast iron mould to heat up to the point where it would make serviceable boolits. I, too, think the base being filled out is essential in this caliber, but then I view it as a black powder round (exclusively).

I am making the nicest boolits with a Lee six cavity Big Lube design I got from Dick Dastardly. The bases a square, the sprue cuts cleanly, and the mould heats up with three or four cycles. I use iron moulds for the precision, long range gunz, but really think those aluminum moulds are the bee's knees for production, cowboy boolits.

[Trailblazer]

Another thing that might help base fillout is to loosen the sprue plate a bit if you have it tight. That gives it a little more venting.

[Don McDowell]

Kirk those RCBS mold sprue plates are a bit thicker than other molds so you need to worry more about preheating the sprue plate than the mold.
Also make sure there's no oil left under the sprue plate thats creeping into the opening and causing the lead to wrinkle around the base. Not sure what RCBS uses for oil when they ship the molds, but it can be a bugger to get all of it off,and out .

I'm with trailblazer you might need to loosen the sprue plate just a bit to get better venting, and be sure and leave a big puddle if bottom pouring or hold the ladel to the mold just a bit longer to get better fill out.

That bullet sure shoots good in my bisley, and one of these days am hoping to stumble onto a good deal on a rifle so I can cast more of those bullets.

[KirkD]

Very helpful advice, fellows! Thank you for mentioning details that I didn't even think of, but do make good sense.
One other question. One of you mentioned zinc wheel weights. How do I avoid getting zinc in my melt? Does it have a lower or higher melting temp?

[Last Spike]

Higher melting temp, Kirk - when melting the wheel weights down, you don't want to get the temp too high as the zinc will melt into the alloy mix and cause additional issues. As to zinc's melting point, I can't recall the temp, but definitely higher than lead.

[KirkD]

I looked it up. Looks like it is 787 degrees F. It sounds like I should stay around 700 degrees with my melt. I've just got a simple set-up .... Lyman pot on a camp stove and a Lyman ladle.

[Le Loup Solitaire]

I cast and shoot quite a bit of 38-40; I use Lyman mold #401043 and its an easy bullet to cast, being short and fat. Some of the causes of the problems you have described include; temp being not high enough, a bit of zinc in the melt, and/or trapped air in the mold/ air not getting out fast enough. A whole chapter can be written about avoiding zinc contamination or working around/with contaminated metal. Assuming that you are using contaminant-free melt lets go to the "air prob". The sprue plate should not be too tight...it should swing free of its own weight without being sloppy-fit. Some folks like to enlarge the sprue hole, but thats not always necessary. The stream of melt coming down from the pour nozzle may be too fat for the hole and not letting the air get by it (the valve is opening up too much). Try reducing that so that the stream goes in with a little room around it. Also if you can get a roll of 60/40 solder and put a bit into the melt...the 40 is tin and even a little of it will increase the "fluidity" or pourability of the melt. Keep your melt fluxed and clean. I use a 1/4" slice of wax from a candle. It starts smoking right away, but toss in a lighted match and the smoke (but not all of the stink) will burn away in a moment. Scrape the sides and the bottom of the pot when fluxing and skim off the dross, crud and oxides when you do that. Flux whenever the metal starts to act and/or starts to pour "stringy"/"clingy". Some casters like to use Marvelux which is a fluxing agent that does not smoke or stink; I've used it, but the candle is a lot cheaper $-wise. When you pour..with the temp up, let a puddle form on the hole so that when the bullet shrinks it can get some more melt thru the hole to feed the shrinking. Let the sprue harden; some people count to five or else use a second mold to allow time for the sprue to really set up. It turns to a duller gray as it does that. If you get into a rush and cut the sprue when it is still soft then you will get smear(s) across the top of the blocks and on the underside of the cutter plate. That is a royal pain and has to be removed or else it will continue to build up and really ruin things. There are a few ways to remove the smears; the one I use is to take an ingot and using one of the corners-rub the smear. The ingot corner seems to absorb the smear, but the bottom line on that is to avoid the smearing to start with. With a little tin, no zinc, the right temp, rythm, a well adjusted sprue plate and stream of melt you should have no futher trouble knocking out good castings for your 38-40. LLS

[KirkD]

Okay, I can see I was messing up in two ways. First, I was knocking the sprue plate open when the lead puddles on top were still almost liquid. I'll wait about 7 or 8 seconds next time. Secondly, my sprue plate was so tight I had to hammer it closed with my wooden club. I'll definitely loosen it up a bit like Don and Le Loup Solitaire and some others suggested. In the meantime, here are a couple photos...

The two bullets on the left are unlubed. You can see the flat base on the far left one and the rounded edge on the second from left. Lubed and sized to .401", they weigh 188 grains with the flat base and about 187 grains with the rounded edges. The brass is Starline. I've loaded up 5 rounds of each to see what affect the rounded edges have on a 5-shot group at 100 yards. I'll post the range results with photos of the targets later this week.
http://img.photobucket.com/albums/v497/3855Win/38-40-bullets.jpg

This is my 38-40 Winchester Model 1892 made in 1913. It's nothing fancy, but it's a good honest gun that no one has ever messed with (i.e., original finish on wood and metal). It looks like it has earned its keep over the years, with only about 50-70% blue remaining on the barrel, but the bore is very nice, which is why I bought the gun .... strong, sharp rifling the whole length.
http://img.photobucket.com/albums/v497/3855Win/38-40.jpg

[mooman76]

When you are smelting if you pay attention you can spot the zink WWs right off. I don't cook my WWs, I just melt them. I don't have a thermometer but the lead isn't going to gt real hot because I keep adding as they get melted. If you are paying attention you see how long they take to melt and if a WW or two takes longer to melt than the other and sitting there floating all by it's lonesome it will be zink since the melting temp is higher than the others. Just discard it.
As far as when to open the mould you can see the lead puddle turn to a dull color when it hardens on the spue. I usually give it about 2 seconds more and then knock the sprue. It kind of depends on the size of the bullet too. A larger and heavier bullet will take a little longer to solidify inside. If you see the sprue taking out chunks of lead then you know to let it sit a little longer. It's just something that comes with experience and from the looks of your bullets you are coming along fine.

[no_1]

Thanks a lot guy! Now I have to find one so I can load for it. Levers have always had a soft spot in my heart.

R.

[Don McDowell]

Kirk there probably won't be much difference in accuracy,,,, but,,,, I'ld shoot the beveled base bullets last , as there's a fair to middlin chance you'll be mining some lead in the bore , brought on by some blowby gas cutting . If you shoot those first be sure and clean the bore good, as the leading left will tear the other bullets and what a mess that might make.......

[KirkD]

Don, that sounds like good advice. If things work out, I'll head out to the range at lunch to try these loads out.

[w30wcf]

Kirk,
Lots of good advice from our cast bullet enthusiasts. Only a few things I can add:

Preheat the mold - I use a small toaster oven for this. When I started doing this many years ago, the bullets from the 1st cast were match grade.:smile:

Use two molds - By doing this, it allows enough time for the sprue to set up on each mold.

Venting the top of the blocks - The best thing I have found is to use a fine grit stone at a 45 degree angle and just barely stone the top edge of each mold block at (DO NOT USE A FILE). About a .005 groove is ideal. It will vent but not let any alloy flow into it.

drop pour - If you are using a bottom pour pot, drop pouring will also allow the mold to vent, providing the sprue hole is at least 1/3 the diameter of the bullet.

Looking forward to your range report.

w30wcf

[KirkD]

More excellent advice. Thanks, John. I never thought about venting the top, but it does make sense. Hope to hit the range over the lunch hour, chrono my loads, and see how accurate they are. If things go well, you may see a range report before the day is over.