Bottom pours vs pressure casting?

[Martin Luber]

I have cast high volumes of mostly Pistol bullets with bottom pour furnaces, no problems.

Doing 30 can rifle bullets lately and I am not getting good base fillout with a Lee 6 cavity when bottom pouring. I switched to pressure casting by placing the nozzle in the sprue plate and started getting good results.

Is this typical or is this new mould dirty or not seasoned?

Thanks

[Four-Sixty]

I think with the pressure casting you have a lot more control over base fill out. Experimenting with technique I've gone too far, even getting lead to go into the vent lines on some molds leaving little "wiskers".

[762sultan]

Just purchased several old Saeco molds that prefer pressure casting. One is a 301 truncated bullet and the other is a 425 grain 45/70 bullet. They seem to drop undersize bullets so I have to resort to beagleing them to enlarge the diameter about a thou of an inch so they would size properly in the size die.

[Rcmaveric]

Every mold has its personality. Pressure casting is a trick in the tool box.

Sent from my SM-N970U using Tapatalk

[charlie b]

I only cast for rifle right now, .308, 2 cavity molds.

I have tried pressure casting with a bottom pour as well. It does fill out nicely, but, if my pot was full (20lb) I would get finning and/or whiskers and/or 'leakage' around the base/sprue plate.

Getting a good base fill out for me happens when I leave a good puddle on the sprue and have proper temperatures of the mold, sprue plate and melt. Also accurately pouring into the mold helps (instead of splashing off the sprue plate :) ).

Having said that my 'good' vs 'bad' bullet ratio is usually 50% when I add in the weight sorting. 25% get tossed for visible flaws. Another 25% for low weight.

You might try ladle pour with a spout, like a Lyman or a bit more capacity ladle.

[country gent]

Pressure casting can make a big difference in castings both weight and visual. It keeps the pour molten longer and pushes air gases out better. Watch the level in the pot as as it gets lower the "pressure " drops off quickly. experiment with temperature and alloy also they make a big difference.

[WHITETAIL]

+1 with Charlie b,
I have been casting for more
years than I will admit.
( being 65+ years)
And I find that if you get the
mould and lead up to temp.
Leave a good puddle on top
bang you get a full boolet.:castmine:

[Conditor22]

good fill out:
1) mold hot enough ( I like 400° on a hot plate)
2) alloy/lead hot enough -- 680° to 720° ( the softer the alloy the hotter I need to go)
3) not enough tin/pewter
4) not leaving a big enough puddle on top
5) not "bleeding the spout (squirt lead into the catch basin below mold to get rid of the cool lead in the spout so it doesn't get into the cavity) before casting the first cavity
6) lube left on the bottom of the sprue plate.

[fcvan]

I have four 30 caliber molds, three are Lee, one is NOE. Two are 150 gr, one is 155, and one is 230. I learned a long time ago that I get good fill out and clean sprue cuts depended on several things. 1) allow temp, 2) mold temp, and 3) how the cavities are filled.

Using two cavity molds, I let the stream hit the sprue plate slightly to the left of both sprue holes filling both at the same time. This causes the sprue plate to stay hot and the alloy to swirl into the holes. When the sprue alloy material has visibly hardened the mold gets opened.

Bottom drop furnaces produce more pressure than using a Lyman or RCBS ladle due to not having as much weight in alloy. I started out ladle casting 45 years ago, started bottom pour furnaces shortly after. I have cast an unreasonable amount of boolits through a Lee 10 pounder, wore it out, bought the parts and rebuilt it.

I have watched a video from the 1930s of a guy casting with a 10 cavity mold using a bottom pour furnace. He just moved the mold as each cavity filled in one continuous pour. Try the suggestion of the other previous post. Find what works and go for it.

[Dusty Bannister]

Since one of the members posted having issues with a Saeco mold, this reminded me one should look at the size of the sprue hole in the plates. I had problems with the Saeco #221 which is the 22 cal gas check bullet. They had changed to a smaller hole in the plate. The mold was not cut correctly and would not accept a gas check on the gas check heel of the casting and was returned. The replacement mold came with the original large hole which nearly exposed the entire bullet base.

The smaller hole demanded pressure filling, the larger hold distorted the base. I was able to acquire one of the old plates and drilled it slightly larger and after polishing the sprue plate and hole, it now casts better from a bottom pour pot. Just keep in mind that the sprue hole also has a lot to do with ease of casting from a ladle and bottom pour furnace.

Pressure casting can be a great help in getting good mold fill out when working with a newer mold. It helps to develop that oxide formed on the cavity and speeds up the break in of a mold.

[fredj338]

I find every mold is a bit diff. Some will need pressure casting some not. In multicav molds I sometimes have a certain pattern I need to fill to get all the cavs producing good bullets. Haven't figured that one out yet.

[Mitch]

I used a lee 4-20 bottom pour for a long time.then one day Country get taught me how to ladle cast 500 gr 45 bullets.now i have kinda got my own way of doing things.i have never had good luck trying to pressure cast with the bottom pour pot.The ladle is where i pressure cast.the smaller short pistol bullets say under 350 grans or so bottom pour just fine in most molds.I use the ladle i think it is a lyman with the hole drilled a bit over sized.I got it this way in a box of junk at an auction about 30 years ago.i use to for long and heavy bullets.I put the ladle spot right in the sprue plate hole.then let the little bit of lead left on the ladle run over the top of the mold to keep the sprue plate hot.i have a 200 gr 308 mold that i can get decent bullets from with the bottom pour but the mold really shines with the ladle.the small amount of lead in the ladle seems to be just enough to get realy nice bullets.while pressure casting with the bottom pure is just way to much.it make a mess for me finning whiskers and pluged vent lines.