Problem: lead bristles forming in air grooves

[KirkD]

I had an RCBS 25-20 PB mould that I had a fellow use before I got my own casting equipment. He cast up over 500 bullets for me with no problems judging from the bullets (seams are almost invisible).

I just sold the mould to another fellow and he is having trouble. First of all, the two halves were not closing tight unless a lot of force was used. The alignment pins were adjusted and now the mould halves close tightly with ease. The problem is that he is getting lead spines or bristles from the melt leaking into the air escape grooves, even though the two halves are tight against each other. My bullets cast from the same mould show no signs of any bristles, so this seems to be a recent development. He has started using a bottom pour pot and is using melted wheel weights. Could the lead bristles be due to the higher pressure melted lead shooting into the mould and/or a too high melt temperature? .... or is there another explanation? How can he keep these bristles from forming? I have casted five different bullets for myself since I started casting, but have never had bristles forming in the air escape grooves for any of them, although the smallest caliber I've casted is 38-40.

[HangFireW8]

Could be: too hot, too much tin, too much melt pressure.

-HF

[geargnasher]

Could be: too hot, too much tin, too much melt pressure.

-HF

+3.

I never see those whiskers as an issue unless they turn into fins, which IS a problem with block closure. The whiskers will be totally gone from normal handling by the time loaded ammunition is placed in the box.

Gear

[runfiverun]

tell him to not pressure pour.
my 22 mold will whisker if i pressure pour.
and a mold that pours that well is a blessing. needing little or no tin and lower alloy temps once the mold is warm.

[noylj]

Whiskers mean that everything is optimal and you are getting complete mold fill-out. Tell him to cut them off and be glad that everything is so perfect. Those bullets are winners.
He can either slow down his casting speed or lower the melt temperature, but he is not going to make better bullets.

[KirkD]

Thanks, gents, for that information. Now you got me thinking it is I who must be doing something wrong, since I never get whiskers on my cast bullets. My bullets are completely filled out, though, so I'm not worried. Perhaps my melt temperature and Lyman ladle are less conducive to whiskers.

[snuffy]

Kirk, you say you're ladle casting using a lyman ladle. I bet your buddy is using a bottom pour pot, then holding the sprue plate tight against the pour spout, IE, pressure casting. The difference in pressure between your method and his, is considerable.

The "whiskers" are of no concern. They usually can be whisked off with a fingernail, before sizing them.

[9.3X62AL]

I agree with the consensus view expressed above, that all is well with both your own and your friend's casting efforts. Keep right on pouring, both of you.

[Freischütz]

HangFireW8 covered it nicely.

[HangFireW8]

HangFireW8 covered it nicely.

Thanks, Freischütz. But I left out geargnasher, runfiverun and noylj's excellent point- nothing is actually wrong, but there is a good chance you can eliminate creating whiskers if you really don't want them.

-HF