boolit base voids

[chevyiron420]

ok guy's i have a question. i have one of the cheep lee molds for 185 gr. 303 bullet i bought about 5 years ago. i havent used it much untill now, and i need it! i keep getting too many boolits with little bubble voids in the base. otherwise they look good. its a single cav mold and it doent seem to have any venting on the top of the blocks. is there anything i can do without re-inventing the wheel here? i have worked with different temp setting, faster--slower pour, tilting, sacrificed some small animals. i am useing a lee bottom pour, and it works perfect for all the other molds.-phil:castmine:

[454PB]

Those air pockets usually appear in the larger diameter boolits, and are caused by too much flow/too fast filling. I realize you have slowed your pour rate, but it needs reduced pressure as well. Try using half a pot of alloy, that will reduce the pressure of the fill. Another thing to check is the spout on the Lee pot. Over time, they get restricted by crud buildup, which has the effect of increasing the pressure......kind of like placing your thumb over a hose end to increase the pressure. Use a nail in needle nose pliers to clean it while it's up to temperature. Raise the fillvalve, let the lead flow, and then insert the nail and ream it out. I use a dental pick for this, but a nail works as well.

[Dale53]

The molten metal and the mould should be hot enough that it takes several seconds for the sprue to solidify. Adding as much metal as you can to the sprue plate keeps the sprue plate hot and the sprue liquid long enough for the bullet mass to pull down molten metal into the "void" as the bullet cools. This fills the void.

Hope this has been helpful.

Dale53

[grumpy one]

If it isn't what others have said, it might be worth checking for something even more simple but perhaps less obvious. If you have put oil or some other lubricant on the top of the mould and it has transferred to the sprue plate, you'll probably get what you have described.

[JSH]

A friend called me this past weekend, having the same problems only with a Lyman SC 45-70 535 grain mould.
I talked to him a bit and tried to help him through it. Everything I told him to try he stated he already did.
Mowed the yard and went over there. First off his mold was a mess, took me about a half hour to clean all the lead smears off, vent lines etc. Jumped him pretty hard for being so sloppy.
Somthing that I learned, read here stuck with me on this subject you mention. I fooled around for about an hour and had it chunking out great biggun's that looked and measured very well.
All I did was bumped his heat about 50 degrees, RCBS pot, and then instead of pouring right through the center of the sprue cutter, I let the stream hit the edge and swirl down into the mould.
He could not believe the difference. I made about 200. We weighed a few and they only varied about 1 grain, he is sorting by weight.
Hope maybe this helps.
Jeff

[1Shirt]

Words of wisdom from JHS. In addition, suggest he try Bullplate! It also helps a great deal.
1Shirt!:coffee:

[NVcurmudgeon]

I used Bullplate Lube for the first time a couple of weeks ago. The percentage of keepers was my highest ever. The bases were nearly all perfect.

[floodgate]

chevyiron:

"...it doesn't seem to have any venting on the top of the blocks. is there anything i can do without re-inventing the wheel here?"

You can provide venting at the top of the blocks by one careful swipe of a fine file across the top inside edge of each block, making a very slight (no more than a "line of light") 45* chamfer leading from the pour hole out to the front and back edges of the blocks. This often helps with the problem you are having.

floodgate

[chevyiron420]

thanks floodgate, ill try that! i assume you mean 90 deg. to the parting line of the mold? thanks to everyone for the help!-phil

[floodgate]

chevyiron:

NO! NOT 90* to the parting line, but along it, front-to-back. Just a very light chamfer along the top edges of the blocks where they meet, under the sprue-plate. The other would work ,but would be hard to do without raising a burr.

floodgate

[lurch]

An observation and a question:

1. I can agree with 454PB - the flow rate is a big contributor to bubbles near the base. Slow it up and not loading the pot all the way makes for a lot more keepers when I cast 45's & 44's. I don't notice the problem as mch with the 38's but it is there.

2. Dale: I load my sprue plates up to just about ready to run down the side of the mold. If I don't watch the flow rate, I still get a lot of base voids. I am casting hot enough that I have time to give half decent inspection to the last drop before I even think about cutting the sprues - 15 seconds or so as a guesstimate (never actually timed it). Bullets come out a little bit "galvanized" looking. To me this does not seem to help too much though I do get much better fill out of the base edge casting like this. To me it seems like the lead inside the mold freezes up before the bubble can make it out of the fill hole and let the still molten portion of the sprue in. Any thoughts on that? :confused:

[pdawg_shooter]

Try a ladle....cured the problem for me.

[leftiye]

Lurch,
I cast hot enought that the sprue takes a few seconds to solidify, and time until the sprue cut off is mushy is a few seconds more. This way the voids draw metal from the puddle and fill up. Base voids are a thing of my distant past. Use a mold heater if you have to to keep the mold hot enough. As mentioned earlier, you can improve base of mold venting by beveling the inside top edges of the mold a little.

[454PB]

Try a ladle....cured the problem for me.

I agree, I've never had voids with a dipper. I just can't go back to such a crude way of doing things[smilie=1:

[jhalcott]

I get these "dimples" or torn bases AFTER I've been casting for a while. I'm not sure if it's because I am getting tired or rushing to empty the Lee pot. Doesn't matter what mold/ molds i'm using either. When I sort the pile, those with the base dents go into a pile for plinking or fire forming . The real bad ones go into the redo can!

[lurch]

Next time I break out the 44's or 45's I'll have a go at a light stoning of the top edges and see if that helps out some.

I'm afraid I'd get a little heavy handed with a file...[smilie=1:

I just can't bring myself to ladle cast anymore. I'm spoiled. The base bubbles are not enough of a problem to drive me back in that direction (not that many of them when I watch what I'm doing more closely).

On reading this through some more, I'm not sure I'm seeing the same thing that other folks are. When I get a bubble near the base, it usually shows up as a partial ring that looks slightly sunken in. Sometimes I'll notice a shiny spot near one end that is the obvious thin spot from the surface of the base to the void. In either case, a little probing with a pick at one end or the other will usually point up a bubble a little below the surface.