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Tippet
12-27-2009, 09:24 PM
Finally got a chance to break in the new mould. My first time casting with a dual, first time with a cramer, I've got a question.

I had a lot of drops where one boolit is perfect and the other has rounded edges on the base. Any guesses as to the cause?

I cast at 750° with No. 2 alloy. For a couple hundred boolits, aside from the ones with rounded bases I only found a couple dozen imperfects. Must have been the first few drops. The rest had perfect fillout around the nose holes, no wrinkling looking real good. Just a little frosty is all.

Next, I'll drop it down in increments to find the coolest temp that still gives good drops. But I'd sure like to figure out what's causing those rounded bases. Not letting the sprue cool long enough?

opentop
12-27-2009, 10:06 PM
Are the ones with rounded edges closest to the handles? It might be that the mold is cooling off to quick at that point. Or it could be a venting problem.

This may sound corny, but try filling that hole first. I have a LEE 2 cavity that wont fill out unless I fill that hole first.

Tippet
12-27-2009, 11:07 PM
OK I'll give that a try. I figure it must be some temp diff betwixt the 2 cavs, whether order or pour of sprue issues,

Springfield
12-28-2009, 12:46 AM
Rounded bases is usually caused by either a venting problem or not haveing the mould hot enough. As long as you aren't tearing out the base of the bullet letting the sprue stay hot is usually a good idea, especially for getting good fill at the bases. Cold sprue plates will cause rounded edges, not hot ones.

Tippet
12-28-2009, 02:10 AM
OK I'll let more sprue pool on the plate and push it open sooner, maybe the thing will heat up better. Something tell me this mould does not have a venting problem. Everyone else who's used one says it's the best.

Tippet
12-28-2009, 08:59 AM
OK I turned up the temp on the stove for preheating, and started filling the rear cav first. I didn't make an effort to allow a bigger pool of sprue, but I picked up the pace. It seems to have worked. So far I've tried it at 750°, 725°, 700°, and 675°. I got good fillout at all those temps, but I got the least frosting (pictured below) at 725° which surprised me. I expected the frosting to diminish directly with the temp. In a bit I'll hit it again at 650°.
http://i113.photobucket.com/albums/n226/tayloroid/cast%20boolits/725.jpg

Tippet
12-28-2009, 10:03 AM
Well at 650° I still get frosting, and trouble keeping the mould hot, resulting in a lot more rejects with poor fillout around the base and lube groove.

Funny thing is, this is the last of my No. 2 alloy. After this is gone, I'll be making up my own and I'll have to go through this again to find the best casting temp for this mold with the new alloy. I think No. 2 is harder than I want for this .45 ACP boolit.

I have a buttload of pure lead, and a whole mess of ingots stamped SN63 which I believe means 63% tin 37% lead. I guess I better confirm that. I have maybe 10 lbs or so of antimony too, but I don't think I'll use it any time soon. Maybe when I get to the rifle boolits.

I also have a buttload of ww, both clip-on and sticky. I guess I'm looking to come up with a fairly soft alloy to promote expansion. I've come to learn softness doesn't make for leading, rather it's sizing, so I think I want to start experimenting with a BHN of around 11. I understand that makes for excellent expansion with the Lyman Devestator.

Lee hardness tester inbound.

Storydude
12-28-2009, 03:40 PM
I"ve been throwing 1Lb Clip on WW to 3 Lbs Stickon ww. No clue on hardness, but I can dent it easily by dropping a boolit onto a concrete floor.

No leading and decent expansion....at least they make Frozen gallon jugs of water explode nicely. :D

Tippet
12-28-2009, 07:37 PM
sticky WW is nearly pure lead, clip-on is abit harder but still pretty soft. Sounds like a good soft mix, just slightly harder than pure lead. Apparantly leading is caused by improper sizing, not soft lead as I used to think. What temp are you pouring that alloy at?

Barnowl
12-30-2009, 01:52 AM
I"ve been throwing 1Lb Clip on WW to 3 Lbs Stickon ww. No clue on hardness, but I can dent it easily by dropping a boolit onto a concrete floor.

No leading and decent expansion....at least they make Frozen gallon jugs of water explode nicely. :D


Around 9 BHN. (.1 Sn, .8 Sb, 99.1 Pb or thereabouts) See this thread for info on mixing alloys and a nice alloy calculator spreadsheet. http://castboolits.gunloads.com/showthread.php?t=67401&page=2
(See post #22 for the Excel spreadsheet attachment)

Kevin