Pressure filling molds?

[44Blam]

So, I heard about this a while back. Basically with a bottom pour pot, you push the mold up to the nozzle and fill the mold...

Last time casting, I did this with an OO buckshot mold (to make slingshot bbs) and it filled a cold mold perfectly. Then I tried it on my warm boolit mold and I got good boolits every time...

Does anyone do this? Is there a drawback to it?

[bmortell]

i do it with a half full ladle pour as i dont have a bottom pour, but the only downside i see is its easier to get "fins" if conditions are right for it.

[smithnframe]

Some of my moulds it works, others not so well!

[Neverhome]

i do it with a half full ladle pour as i dont have a bottom pour, but the only downside i see is its easier to get "fins" if conditions are right for it.

This.
Fins and whiskers.
And depending on the mold, a base flange. My Lees exhibit this more so than my better molds.

[762sultan]

I have a SAECO #301 mold that will only make well filled out bullets by pressure casting.

[Dusty Bannister]

This method is usually more beneficial when the sprue hole is small and the alloy does not fill the mold quickly. Cool ambient temperatures will add to the issue. Some can use it to hurry up the mold warming time since the alloy is forced into intimate contact with the mold surfaces. If you have a spot where the mold is just not filling out, it can help press the alloy into that area as well. Usually after a short period of casting, you can return to your normal pouring method.

With high antimony alloys, there will be less shrinkage so you might suffer mold sticking with better fill out.

[OS OK]

Yah, it works & it works more than not...

* have to have clean mould faces, snug fitting sprue plates and tight moulds
* have to time it just right & drop the mould from the valve just quick enough to make a sprue puddle
* can't run lead really hot, from what I've seen 750ºƒ is 25º too hot...the old Ideals I have will try to fin at the pin in the nose
* can't allow the little drip on the valve to enter the cavity, wipe it with the sprue plate as you mate the plate & valve

* checking each and every base fill-out will warn you before the mould gets too hot, it will tell you your sprue plate needs adjusting, if your plate is bent upwards from hitting it wrong, you will have to fix that & make it snug and smooth again

In this video I was running two pots & two different blends of lead and running three moulds...that made for perfect timing. I was busy the whole time working one of the three moulds and each of the three had plenty of time to cool & bleed off the heat.
The trickiest thing is learning the timing of dropping the mould from the valve and shutting the valve off...if this ole'Dog can do it then no one should have any problems.

[Billwnr]

I get better pressure filling with a ladle than from a bottom pour. Lead comes out faster from a ladle and the weight of the lead in the ladle also pushes down on the "fill". When the bottom pour orifice gets a bit clogged it makes it hard to get a good pour and the lead starts to cool in the mould a bit too fast. My bottom pour orifice needs to be cleaned out.

[Thumbcocker]

Have pressure filled since day one. Just have to adjust the rate of flow with the valve.

[mattw]

I have the RCBS Pro Melt from 1984... I find if I open the rod just a little, I can usually get good fill by getting very close to the nozzel but not touching it. There I times that I pressure fill a few touchy moulds, but you may (will) get some finning at the nose and maybe a vent line or 2. My moulds are so variable that nothing is a constant.

[Walks]

Has Never worked for me. It of course does for dipper casting.

Gave up on it Years ago. Frustrated the bejeezes out of me, My Dad could do it all day long. A pair of #358395HB molds and a "Potters" pot and he could go for hours. Never more the 1% rejection rate.

[beagle]

It's a matter of the proper amount of heat. When starting with a partially warmed mould, I'll occasionally pressure cast. After 2-3 throws, this normally warms the mould sufficiently for it to cast well filled out bullets. But, sometimes this is too much of a good thing and "wings" and "whiskers" will occur on subsequent casts. In this case, you have three options. First, you can slow your casting tempo. You can revert to moving the mould from the spout and revert to "gravity" casting or you can turn down the heat of the melt. Sometimes the latter results in balky results unless you get it perfect. I choose to use the gravity pour after the mold comes up to casting temp./beagle

[fredj338]

I pressure cast with some molds or partial pressure cast, fill with contact then drop the mold down at the end to form the sprue. I get better bullets this way, but some molds will get fins from the vent lines or sometimes the base over fills under the sprue plate if a bit loose.

[Mk42gunner]

I'm a firm believer that molds will tell you what they want, if you will just pay attention. Most of my molds don't seem to care if they are filled with a ladle or from a bottom pour spout with a bit of clearance between the spout and sprue plate.

I have one mold that demands pressure filling to fill properly, a little single cavity Ideal 313445. Actually I think if I vented it just a skosh it would then act as the rest. It is such a pain to change the way I cast, that I haven't used it for several years.

I have one I Frame that just loves the little monsters, and I am about out so I need to cast some more this coming winter.

Robert

[megasupermagnum]

Yes, some molds it works great, some not. If it doesn't work, you will get finning on the sides, the base, or both. As a general rule, I regularly pour cast with a bottom pour, and pressure pour with a ladle. The difference is that a bottom pour normally has 15 to 20 pounds of lead forcing down on the nozzle, which is usually too much pressure for a good casting, but not always. A ladle only has a few ounces. I sometimes pour with a ladle, but at the moment I can't think of anything I pressure pour with a bottom pour.

[trixter]

I shoot a LOT of 9mm, and have been using a Lee 2 cavity 358-105-SWC. I tried the 6 cavity mold but could not it to work for me, and I am sure it was me. Using the 2 cavity I have learned to pressure cast and I am in no hurry so this works well. The problem with the 6 cavity that I have is that one of the center cavities will not release the boolit. Maybe I will send it back to Lee and see what they have to say. It would be kind of nice to speed up the operation. (Make more, shoot more).

[onelight]

I shoot a LOT of 9mm, and have been using a Lee 2 cavity 358-105-SWC. I tried the 6 cavity mold but could not it to work for me, and I am sure it was me. Using the 2 cavity I have learned to pressure cast and I am in no hurry so this works well. The problem with the 6 cavity that I have is that one of the center cavities will not release the boolit. Maybe I will send it back to Lee and see what they have to say. It would be kind of nice to speed up the operation. (Make more, shoot more).

I have had one that did that and I got to where if it did not fall out I would just leave it in the mold until it did and skip that cavity when it stuck , was faster for me than fighting that one cavity.

[OS OK]

Use a Q-Tip and rub it around the edges of that cavity on the parting faces...if there's micro burs there they'll grab the cotton.
Try taking a popsicle stick and carefully rubbing the edges of that problem cavity, sometimes there are micro-burs left from the machining, can't hardly see them but if they are there they'll hold a cast well enough to make you whack the mould to get it to jump out.

[trixter]

Use a Q-Tip and rub it around the edges of that cavity on the parting faces...if there's micro burs there they'll grab the cotton.
Try taking a popsicle stick and carefully rubbing the edges of that problem cavity, sometimes there are micro-burs left from the machining, can't hardly see them but if they are there they'll hold a cast well enough to make you whack the mould to get it to jump out.

.

Thanks for the tip. I'll have to give it a try.

[bangerjim]

You use the technique that works for your molds. All are different. Yes, I use pressure casting a lot on certain molds I have.

banger