scratching my head...

[jimb16]

Today I was casting some rifle bullets and had a problem. About 1 out of 10 bullets didn't fill out right. This was the same alloy mix that I always use. 9 of the 10 would be perfect. I added some tin; no good. I upped the temp; no good. Mold is an old stand-by used many times with no problems. No oil on the mold. It is stored in a sealed barrel with my other molds none of which are oiled so no source for contamination. Casting speed was a normal fast pace. I left a nice puddle of lead for the sprue. Puddle took several seconds to solidify so I know I wasn't casting too cool. I'm not new to casting with 40+ years of practice. Any ideas what could have caused this problem? Wrinkled bullets are a nuisance! And yes, I did flux several times. And the puddle did "suck" in as the bullet solidified.

[Bzcraig]

Though I can't point to the issue, it seems that it is random enough to suspect something in the cadence possibly?

[Guesser]

I would suspect a venting problem in the one cavity; you didn't state what size mould or what design. Clean the vent lines and see.....

[farmerjim]

Was the bad bullet from the same cavity?

[OS OK]

Hard to tell without pictures but I'd imagine that something was gassing in the cavity.
Wrinkles are obvious but a gassing lube looks like a 'wantabee wrinkle'...

[Echo]

I would suspect a venting problem in the one cavity; you didn't state what size mould or what design. Clean the vent lines and see.....

Plus One - if the problem is a mis-shapen side, rather than the nose or base...

[jimb16]

No problem with cadence. Normal casting rhythm. Vent lines were clean. In fact some of the bullet noses had vent line whiskers! Single cavity 8mm 185 gr. plain base. And the wrinkles were usually not in the same places. Some were on the nose, some on the sides and some on the lube rings! I even had a couple on the bases. I used a straight down pour from the pot; an old Lyman bottom pour. Mold was set 3/4 inch below the spout. Guide was set so that the pour was consistent in the center of the sprue hole. Like I said, I'm an old hand at casting and this has me baffled.

[Moonie]

I've had days casting where no matter what I did I couldn't make good boolits. Other days everything is perfect and they rain perfect from the mold.