Big heavy bullets and base voids?

[Blackwater]

Fellows, I have a Saeco #745 mould for my BPCR Browning 1885. I tried WW's in it and got a VERY high scrap %. I don't recall the scrap rate, but it was WAY over 30%. This doesn't happen with plain lead/tin alloys. What's going on? Why do WW's get voids in the base while the plain lead/tin alloys not do so???

It's hard to find real good plain lead at the junk yard, and I'm too cheap to buy the foundry store stuff, so I'd really like it if I could get good WW bullets out of this mould. Any help you can offer would be appreciated.

It's a sort of Creedmoor style bullet with a small flat point, and weighs 533 gr. with 1:30 tin/lead, and drops at .4597" nominal. Shots pretty good with lead/tin, but .... well, just how dumb would I have to be to NOT want to shoot cheap WW bullets? Thanks for any help.

[JohnH]

You don't say if you are adding any tin to your WW, this coul dmake a difference, but in casting 405 grain 458 bullets I have found that letting the stream pour a bit longer than I might with a lighter pistol bullet of the same caliber does make a difference. I'll refrain from from my semi half educated sort of don't know anything wild guess as to why this occurs, but it does boil down to the idea that the bigger the bullet, the bigger the sprue should be. Don't know if the idea is worthwhile but it did reduce my rejects, as did not cutting the sprue quite so soon after the pour.

I use a bottom pour pot, hold the mold about an inch below the spout, and add 2% tin to my WW. I read these days of folks not adding tin to the WWwith exellent results. I reckon I do this because I don't know how not to.

Edit, added this....Most likely the antimony is the culprit, the difference between melt and cool rates being different between the two alloys, (lead antimony as opposed to 30:1 lead tin) most particularly that the antimony forms a lattice on cooling and most likely results in a somewhat more brittle alloy that when cut too soon tears away metal rather than actually cutting it.

[KYCaster]

Holes in the base mean the sprue is freezing before the boolit. Freezing part sucks lead from the liquid part. You may try lowering your pot temp. with the WW and bigger puddle on the sprue.
Roof flashing, Xray shielding, telephone cable sheath are all very nearly pure lead. Usually .25 to .5 % antimony and traces of arsenic. Most scrap yards have some of this available. Go to your local plumbing supply and ask for 50-50 solder. Talk to them for a while and you should be able to get it under three bucks a pound. That's less than six bucks a pound for Tin. Not bad compared to the guys advertising in the gun rags, and will mix very easily with your scrap lead.

[powderburnerr]

Blackwater ,you dont say if you pour or ladle .I get a lot of cicular voids when using ww and big bullets I went to ladle casting and leave the ladle full of lead married to the spru hole for a 5 to 7 count before making a spru and it works quite well . the other thing that could be causing your problem is contaminates on the bottom of the spru plate.......... Dean

[454PB]

A bullet that big takes a long time to cool. You may be opening the sprue cutter too fast, that will cause a void in the bullet base directly under the sprue hole. If you are using a bottom draw pot, filling the cavity too fast will also cause pockets of air to get trapped between the sprue cutter and bullet base. When the pot is full, you need to throttle down the flow.

[Buckshot]

..........I have the mould and use that boolit sized to .452" in my Whitworth muzzleloader.

http://www.fototime.com/F3D653267DC9226/standard.jpg
It's the 2nd from the right and as you can see, the base is near perfection, but this is a lead-tin alloy.

What will cure the problem, but is a bit messy is to use the "Standing Wave" process. This from an article by Dennis Marshall, or maybe Frank Harris. I dis-recall now and my apologies to the author.

It's easier if you have a SC mould, or use a DC as a single. If you use a bottom pour pot you keep the valve open after you see the cavity 'bounce' full, and let the alloy continue to sluice into the sprue atop the cavity. You can tilt the blocks slightly so the excess runs off neatly into an ingot mould. All you need is about 2 seconds extra pour. Let the sprue cool a few seconds beyond seeing the alloy harden, then swing the sprueplate.

You're keeping the base of the slug molten. The slug hardens from the nose up and the outside toward the core. That extra couple seconds allows the core at the base to draw in sufficient lead to be complete. You should see perfect bases.

If you use a dipper, when you roll the mould blocks and dipper vertical you pull the dipper up away from the sprue and let the alloy continue to pour into the sprue. If you leave them in contact the lead will freeze in the dipper nose and do you no good. There isn't enough heat in the thin bit of lead in the dippernose to do the sprue much good.

You might also check to be sure the spruecutter is sharp so it cuts and is not tearing the sprue.

You probably aren't seeing this with a lead-tin mix is that it's usually cast at a higher temp so the alloy in the cavity and sprue remain molten a bit longer. Plus it's easier to cut then the more brittle antimony mix.

..............Buckshot

[BruceB]

As I get deeper and deeper into this business, I find that SOME things are getting simpler and simpler for me.

With wheelweight bullets all the way from 100 grains up to about 570 grains, I have NO trouble with fillout, voids, base cavities, etc. etc., and I NEVER move the RCBS pot's setting from absolute maximum, which is 870 degrees. From single-cavity RCBS moulds, my .416-365s vary less than one grain, and my (former) .50-565s were about the same, both cast with my non-patented "BruceB" high-speed method. For that matter, I've also been leaving the temperature setting at max for pure lead and for the very limited amount of linotype I've had in the last few years.

The high temperature gives TIME for the molten alloy to fill all the nooks and crannies, and the sprue stays liquid long enough to continue feeding the cavity as the new bullet solidifies. The sprues clearly show the dimple caused by the bullet drawing its last bit of metal from the liquid on the sprue plate.

If a swirling motion can be imparted to the alloy as it goes through the hole in the sprue plate, the commotion inside the cavity can help get rid of trapped air, but really, if the temperature is high enough, gravity will take care of it. Having the stream of alloy contact the side of the sprue hole as it falls will give a lot of turbulence in the mould (I think....never have managed to get a good look in there!).

Many seem to have a reluctance to crank up the temperature, and I suspect this might be at least partly based on not wanting to add any time to the solidification process, which is a slow event to be sure. I refer you to the technique which uses the WET (not "damp") cloth roll for speeding-up the routine. I simply see NO downside in my bullets cast with the speed-casting method.

[longhorn]

Kudos to BruceB on this one! I use the same Saeco 745 as my match bullet, casting wheelweights at 850F (Waage pot). I used to have a terrible percentage of cratered bases when using a turkey burner setup, fewer problems with the Waage, but finally found success with the wet rag "quench" process. My casting speed is way up and my reject rate is _way_ down. OTOH, my Brooks mold for a 420gr flat nose truly hates having the sprue cooled. Try the speedcasting way.