problems with sprue

[50-90]

i need some help. im using lead pipe sheathing and tin for a 16-1 mix. a mp mold in 45-270 with hollow point pins. the problem is it tears the base. this happens with a quick cut or a long wait. whats up?

[jsizemore]

Does it do the same thing when you use the non-hollowpoint pins?

[Bzcraig]

I'm thinking the pins aren't up to temp. Are you using a hot plate to heat your mold?

[50-90]

I use a hot plate to preheat. I have not tried without the hollow points. This continues even after 200 or more bullets. Pot is running at 725 to 750. Ladle poured.

[jsizemore]

'Cast hot and fast' is the hollowpoint caster's mantra. When you cut the sprue early, it gets 'torn' from the bullet base. Depending on your priorities, if that's what it takes to get filled-out, consistent boolits, then go for it. I try to keep my alloy temp 100deg above liquidus and time my sprue cut so that it's 'cut' and not 'torn'. Sometimes to get the desired results you have to make compromises. I suggest try casting without the hollowpoint pins and time your sprue cut so it doesn't 'tear' and adjust your results with the hollowpoint pins in place. The reason I like cut and not torn is I don't end up with lead smear across the top of the mold blocks or sprue plate. I know I could add lube to keep the smear from happening, but patience will also work.

[tomme boy]

Tearing the sprue, or are you getting flashing from the plate being too tight?

[50-90]

No flashing

[jsizemore]

How about some pix?

[tomme boy]

Pics would definitely help.

[DLCTEX]

Bullplate lube on the mould helps IMHE.