Large Cavity Casting

[StrikerOmalley]

A while back I purchased a large volume 4 cavity mould (513-850) and I've been pretty happy with it. Each bullet is close to 850 grains. My only issue seems to be flyers every once in a while. I typically get three rounds with a 1-2" group at 100 yds, then a fourth is 10-15 inches off the group center.

I've repeated the test a few times and I've concluded that voids in the flyers are causing them to veer off course.

I've begun weighing the bullets but I'd guess that is only so good for defeating the issue. I'd like to get at the root cause. Is there any specific guidelines for casting with large volume moulds?

I'm currently using a Lee production pot (bottom pour) and I'm also using a hot plate to pre-heat the mould.

Thanks,

[Yodogsandman]

I also had problems using the 10 lb. cap. Lee Production Pot with 505gr .58 minnie balls. I resorted to go back to ladle pouring them. The flow just wasn't fast enough in the bottom pour to maintain mold temperature. A Lee 4-20 Pro Pot has an adjustable flow and would be better (have not tried it). Weighing your boolits and using a hot plate are both good ideas.

[Tatume]

I also prefer ladles, but you may need a larger ladle to pour four 850 grain bullets. Take a look at the Rowell #1.

http://www.rotometals.com/product-p/casting_ladle_bottom1.htm

Make sure your alloy and mold are hot enough to keep the metal melted in the mold long enough to vent all the air. I prefer frosted bullets, as that is a good sign that the bullets were hot and molten for a long time.

Continue pouring after the sprue plate is full, and let the plate over-flow back into the pot. This keeps a supply of hot, molten lead in contact with the sprue area, and also keeps the sprue plate nice and hot, furthering the goal of keeping the interior molten. The longer the interior is molten, the better it is able to expel air.

Take care, Tom

[Catshooter]

I would love to see a pic of both boolit and mould.


Cat

[1johnlb]

I know nothing about large calibers except my shoulder hates them, but could you be experiencing lube purge. I know it happens on smaller like 30Cal rifles. I have one rifle that has a flyer every 5th shot because of lube.

[masscaster]

Run a Wet Patch, followed by a dry patch every third shot. I do this with big bores regardless if it's Smokeless or Black Powder.
If you get in the habit of doing it every other shot you'll find accuracy to be way better. Most of this has to do with bearing surface, and fouling, even with Smokeless powder.
Wet Patch, Dry Patch, Shoot, Shoot. ; )

Hope this helps.

Jeff