Do you agree?

[madcaster]

Couldn't sleep early this morning,about 4AM got up and started casting.
Got to thinking,smoke coming off my bald spot and all don'tcha know,that maybe a round ball mould and nose pour have something in common-being that while the cavity is filling with lead,that any trapped air is actually NOT being trapped,that it is being forced out the top by the lead volume pushing it up.
Here is a couple of pictures of my setup for today....
Jeff Tanner gang moulds,best there is for round ball moulds,bar NONE!

[charlie3tuna]

Jeff Tanner gang moulds,best there is for round ball moulds,bar NONE![/QUOTE]

I'm old, fat and lazy. Can I have a link? Thanks.

the other charlie

[waksupi]

I had no idea Jeff made gang molds. Price?

[9.3X62AL]

I did the same thing today, got up early and fired up the pot. Lymans #358429 and #410032 were in short supply after my mammoth reloading effort the past couple of days, so I took the time with Marie out of town on retail therapy to re-stock the larder. Just two-banger moulds, but I made a pile of boolits.

I've come around to leaving the sprue plates fairly slack on the pivot bolts--the cavities seem to vent more easily that way, and I get a lot fewer rejects--even with lowered casting temps (675*-700*).

[Nardoo]

9.3,
I am with you regarding a loose sprue plate. I always have had better luck that way. Interestingly, I just received a beautiful H.T. Bugg .440" RB mould from Jim at CBE. It is my first Bugg and it has never been used. Well I cast up a couple of hundred balls on the weekend and my, he knew how to make a good mould. The sprue plate pivot screw holds a specific clearance by use of a beautifully made spacer rather than a grub screw captured affair the others use.

Perhaps that is not clear and I should provide a photo but Trevor knew just how much clearance sprue plates needed and made his moulds accordingly. When cold I thought the plate was too loose but I was wrong.

This is my first Bugg but won't be my last.

Nardoo

[montana_charlie]

Got to thinking, that any trapped air is actually NOT being trapped,that it is being forced out the top by the lead volume pushing it up.
I think it's correct to see it that way...unless a load of lead gets dumped in so quickly that a 'bubble' is trapped in the nose. In that event, the venting along the length of the cavity should provide the escape route.

Many ladel casters don't turn the mated mould and dipper upright suddenly...even when casting very large bullets.
By taking a full second (or two) for that motion, the chance of trapping air is minimized.
CM

[Le Loup Solitaire]

Sometimes molds do not fillout entirely due to a couple of conditions. One is the sprue cutter being too tight and this can interfere with venting. A sprue cutter plate should be loose enough to swing freely of its own weight, but at the same time not so sloppy loose so that it can move up and down on its screw/bolt. Another condition that traps air is that the stream of molten lead is the same size as....or thicker than the pouring hole in the sprue plate. A large torrent of lead slams into, but not entirely thru pouting cone and hole so no air can get by as the lead trys to fill the cavity. A stream of lead can vary between a trickle and half the diameter of the pouring hole and successfully get the job done. The distance between the valve and the pour hole is yet another factor which can effect the quality of the cast bullet. This is where the pressure comes from. These last two variables have to be "played with" to determine which settings work best. They also vary from mold to mold. Listing the mold in a small notebook along with your personal comments on the settings will assist you to set it at what works best for you with that particular mold the next time that you use it. LLS

[montana_charlie]

Sometimes molds do not fillout entirely due to a couple of conditions. One is the sprue cutter being too tight and this can interfere with venting. A sprue cutter plate should be loose enough to swing freely of its own weight, but at the same time not so sloppy loose so that it can move up and down on its screw/bolt. Another condition that traps air is that the stream of molten lead is the same size as....or thicker than the pouring hole in the sprue plate. A large torrent of lead slams into, but not entirely thru pouting cone and hole so no air can get by as the lead trys to fill the cavity.
Consider this theory about escaping air and sprue plate adjustment...

Most sprue plate pivot screws are used with a spring washer (I think a wave washer is better than a lock washer).
Either can be socked down so tight the sprue plate cannot lift off from the top of the block.

Tightening the screw just enough to use up half of the spring in the washer makes it possible for the plate to lift if the force is sufficient...but it will immediately drop back flat when under no pressure.

Superheated air will expand with a great deal of force. It is enough to lift that sprue plate (if the screw isn't torqued down)...even if you are holding the pouring spout snuggly against it.

A moderately quick fill of the cavity allows the lead to get below the trapped air which then expands and blows out under the sprue plate. The plate then snaps down (under spring pressure) to create a flat base as the alloy cools.

That (I believe) is why a 'looser' sprue plate and standard size pouring hole work best.

CM

[anachronism]

I always drain the ladle on each cavity. Since I've started doing this, my reject rate is so low it's laughable. I believe that keeping the base of the bullet molten by pouring excess molten alloy over it allows more air to escape before the bullet freezes. I can get bullet bases a guy could almost shave with, they're so sharp. It takes a couple of seconds longer, but no where near as much time is required to remelt & recast defective bullets. Go ahead & laugh, I probably would too.