Losing tin???

[L1A1Rocker]

I'm stumped with a fill out problem on my 4 cavity 359-640.

Background:

Had a 50/50 COWW/Pure with 2% tin in the RCBS bottom pour melter that I drained and set aside. Loaded up with COWW with 1% tin to cast up some solids with the mold. This was the first casting with this mold and it did great after only 4 throughs. This was several months back.

A couple of days ago I drained out the straight WW allow and set it aside and loaded back up the 50/50 mix and put the round hollow point pins into the mold. Horrible fill out, round corners all along the boolit - base and lube groove all very rounded. The ridge seperating the two crimp grooves is not even on some of the boolits its so bad.

I dissasimbled the mold and boiled it out twice, scrubbed it with starting fluid and still had problems. I've varied the temp and pour flow. Finally in desperation I got out my old faithful 2 cavity 359-640 mold and put it on the hot plate. Edit to add: My old faithful 2 cavity mold has dropped near a thousand almost perfect boolits.

Once it came up to temp I tried "old faithful" and got the same horrible results. The only thing I can think of is that I've lost my tin somehow. Is such a thing possible? I'm thinking about trying to add 1% tin to the pot after lunch and see what happens.

Does anyone have any other ideas?

Thanks

[StratsMan]

I'd like to know what you find, too... Got a 4 cav -640 a couple of months ago... even my best casts with the mold and melt screamin' hot still show very little of the ridge between the crimp grooves... I had to slow down, cuz the boolits were breaking in half when I opened the mold (with round HP pins in the mold)... I wondered if it's just too many corners in too small a space at the crimp groove to fill out properly....

[L1A1Rocker]

I'd like to know what you find, too... Got a 4 cav -640 a couple of months ago... even my best casts with the mold and melt screamin' hot still show very little of the ridge between the crimp grooves... I had to slow down, cuz the boolits were breaking in half when I opened the mold (with round HP pins in the mold)... I wondered if it's just too many corners in too small a space at the crimp groove to fill out properly....

I don't think that's it. My old faithful 2 cavity mold of this boolit has produced near a thousand beautiful boolits of this design - the new 4 cavity is a replacment of it. But heck, the solids I did a few months ago came out great. I'm just at a loss for what is going on now all of a sudden. . .

[runfiverun]

pay attention to how you fill the mold.
try slowly swirling the alloy in at an angle..

[L1A1Rocker]

pay attention to how you fill the mold.
try slowly swirling the alloy in at an angle..

I tried that too. Poor straight in, hit it at an angle - little angle, big angle, none of it made a difference.

[Calamity Jake]

Sounds like the vent lines are pluged no letting the air escape and maybe the sprue plate is to tight I like mine a little loose.

There's no way that the tin is just going to disappear.

[geargnasher]

Two things: If you used starting fluid instead of pure ether, realize that you just put oil all over your mould. Starting fluids these days contain upper-cylinder lubricants. Hot, soapy DISTILLED water is about the best mould cleaner there is. The other thing is it was over a hundred degrees ambient a couple months back, and recently has been much cooler. You need to adjust your casting pace to get that mould 20-30 degrees hotter than before.

If you still have trouble, give me a ring and I'll stop by and give it a go with you.

As to the losing tin, it does go away if you overheat the melt and repeatedly skim the oxide scum without reducing it first. Tin oxidizes out at the melt's surface far more rapidly than the other metals, probably because of its lower melt point. I have proven this by performing SG tests of deliberately overheated melt skimmings that were reduced back into their elemental state.

Gear

[L1A1Rocker]

Two things: If you used starting fluid instead of pure ether, realize that you just put oil all over your mould. Starting fluids these days contain upper-cylinder lubricants. Hot, soapy DISTILLED water is about the best mould cleaner there is. The other thing is it was over a hundred degrees ambient a couple months back, and recently has been much cooler. You need to adjust your casting pace to get that mould 20-30 degrees hotter than before.

If you still have trouble, give me a ring and I'll stop by and give it a go with you.

As to the losing tin, it does go away if you overheat the melt and repeatedly skim the oxide scum without reducing it first. Tin oxidizes out at the melt's surface far more rapidly than the other metals, probably because of its lower melt point. I have proven this by performing SG tests of deliberately overheated melt skimmings that were reduced back into their elemental state.

Gear

Thanks Gear. I'm actually using Prestone Starting fluid without the lubricant. Gibson's is the only place I can now get it. I started using that stuff way back in the 90's to clean my IPSC pistols with - works great and drys absolutely clean without any of the tacky stuff left behind. It's been getting harder and harder to find. Thankfully, there's always Gibson's, LOL.

It would seem that I haven't lost the Tin so I'm going to give it a try again this evening. If I can't get this going I'll take you up on it.

Thanks.

[geargnasher]

Yes, thank GAWD for Gibson's, especially Arthur! Lemme know how it goes.

Gear

[MT Chambers]

My understanding is that tin can be skimmed off the top of the melt if not fluxed properly, but that is not your problem, because I use alot of molds with pure lead (no tin) and the molds fill out good and bullets are nice and sharp edged.

[L1A1Rocker]

SUCCESS!!!

In an effort to try and pressure cast as suggested I really cranked open the flow. Well, I didn't really notice a change in flow. Soooo, I ran a needle up the flow spout and WOW did it start to flow. Apparently my problem was that the lead was pouring way to slow and . . . well, ya'll know what that will cause.

Thanks everyone for chiming in to my aid.

Gear, we need to get together sometime, maybe we can toss some burgers on the grill or something.

[geargnasher]

You have a PM.

Gear