Clean bullet bases?

[Wolfmanjack]

Can someone please enlighten me on how to get the most consistent flat/clean bullet base when cutting the sprue? Is is better to cut the sprue right when the lead solidifies? Should you wait a little while after it hardens? Cut it fast or slow? I’m trying to get consistent weights for some long range muzzle loading and the center of my bullet bases are not flat across but some “tear” out a little lead. My edges are sharp and defined but cutting the sprue is where my problem comes in.

[Winger Ed.]

I do it quickly when the top of the sprue goes from shiny to looking dull.

No matter how you do it, there will be slight differences in the boolit's weights.
If ya really to split hairs, segregate them that way.

However; even a full grain or two is usually such a small percentage of their weights--
you also have to eliminate all other variables, and be a really, really good marksman to tell any difference in group sizes.

[metricmonkeywrench]

Don't think there is a best answer here, things such as the mould/sprue plate, lead alloy, puddle cool time and even ambient temp are factors. I only get concerned when i'm ripping craters out of the bottom of the bullet which is not good for the bullet or the mould. Generally for me its striking the sprue plate too soon on a really hot mould

[Char-Gar]

Use a nose pour mold for a clean flat base.

[TD1886]

Don't think there is a best answer here, things such as the mould/sprue plate, lead alloy, puddle cool time and even ambient temp are factors. I only get concerned when i'm ripping craters out of the bottom of the bullet which is not good for the bullet or the mould. Generally for me its striking the sprue plate too soon on a really hot mould

One of my friends and I have been ripping sprues since the creation of casting LOL. No seriousily we have and I'm not talking about a honky road pothole either. It's dead center in the centerline of the bullet so rpm doesn't affect it and we've never ever seen anything harmful it could do the mould. Ours come out flat really with very small tears. You have to wack the sprue plate at the correct time.

I don't agree with cast bullets weighting 1 to 2 grains different. That, in my opinion, makes a difference if your splitting hairs for accuracy and have a capable rifle. Mine usually vary 1/10 grain.

[fc60]

Greetings,

A friend taught me this trick with Iron moulds.

Break the sprue and without opening the mould, close the sprue plate part way so that it covers the little bumps on the bullets. Then, with the mould on a solid surface, A gentle whack with a Lead hammer flattens out the bullet base.

Now remove the bullets as usual.

You will find that when placed on a flat surface they, the bullets, no longer rock.

It also got rid of the "bump" in the middle of the gas check, if used.

Cheers,

Dave

[Dusty Bannister]

Oh that method got another forum in a real uproar. Comments about damage to the sprue plate among other things. Heck, if you want to do that, it is your mold so have at it. As for me, I am not good enough that it will make any difference.

[Carrier]

Most of my molds are Lee but do have a couple Lyman iron ones. After removing the sprue plate and stoning them they cut clean with no craters or smears. I cut as soon as colour changes.

[BLAHUT]

Can someone please enlighten me on how to get the most consistent flat/clean bullet base when cutting the sprue? Is is better to cut the sprue right when the lead solidifies? Should you wait a little while after it hardens? Cut it fast or slow? I’m trying to get consistent weights for some long range muzzle loading and the center of my bullet bases are not flat across but some “tear” out a little lead. My edges are sharp and defined but cutting the sprue is where my problem comes in.

I cut the sprue as soon as it turns frosty. I weigh all my bullets and Segurate them so each weights the same in any given pile, you want extreme accuracy, everything needs to weigh the same....

[Wolfmanjack]

Thanks for the replies gentlemen. Looking for a consensus here as to a universal procedure that may reduce these torn out bases, but maybe that doesn’t exist? I’ll say that with the particular mold I’m asking this question for the best results I got was from using my gloved hand to apply downward pressure in a slow manner. My bullet weights vary and I have been sorting accordingly. Do molten lead temperature variations affect weight significantly?

[Mk42gunner]

I'm not sure if it is the best way, but it works for me: After the mold is up to temp and casting well I do the twist the sprue plate with a gloved hand method. This seems the easiest to me, just don't forget the glove.

Works with most one two or four cavity molds, but with the Lee six cavities, I just use the provided cammed lever.

Robert

[Bird]

It becomes more of a problem with more cavities the mold has. One end of the mold cools and lead solidifies faster than the last cavity filled. Good results can sill be achieved, but the timing is a lot finer.

[gwpercle]

If you are getting tears (divots) in the base where the sprue is ... you have cut it too soon .
I fill mould , then hold the mould and long count , 1,001 , 1,002 , 1,003 ... usually when I reach 1,007 , the sprue has hardened and will cut flat .
You may need to adjust count , 1-2 cavity alum. moulds are different than a 4 cavity brass mould . But by counting you give enough cooling time consistently .
Or ... cast with two moulds , fill one set it down and fill the other , then open and refill #1, set it down ...then open and refill #2, set it down .

Make sure sprue holes have sharp edges . Makes life easier
The Timing of opening is everything and only experience will teach that to you ...

Make sure sprue plate is tight . A loose sprue plate will leave little lumps and not cut flat and level .

I have always opened the sprue with a wood hammer handle , never heard of a gloved hand ... my old hands might not even be able to open a 4 cavity mould ... I just give the sprue plate a nice whack and bust it open .

Gary

[justindad]

Does alloy composition dictate how much gets torn out of the base?
*
Is adding a gas check more impactful than perfecting the sprue cut?

[Texas by God]

I usually cast with three two cavity moulds in sequence.
I fill all three, then dump and refill all three in the same order.
I’m not claiming that it’s the best method, but it works for me.


Sent from my iPhone using Tapatalk

[cwlongshot]

Its accomplished with experience.
No one can tell you, precisely. Be cause its different with temp, alloy mold...

But Ill tell You this, work Too fast, and you will see tear out, work too slow, and then you see humps. Its a practiced feel to get it perfect.

Good luck, in perusing perfection. Its what makes this a art we all adore. All of us can do, but only some can do really well. I'm still working at it too. I see more and more perfect bases. I have only been at it about 35 years.

CW

[405grain]

It's not just the sprue tear out & leaving a pit in the bullet base, there's also another issue as well. Tearing a pit in the back of the bullet is usually caused by not letting the alloy fully solidify. There could be other reasons, like a dull cutting surface on the sprue plate, etc., but not waiting long enough is the usual suspect. Now when this happens you might also be getting a lead build up on the bottom of the sprue plate. This could cause everything from lead streaks to a thick and annoying build up. The best practice that I've found is to look for the "color change" before opening the sprue plate. Let the alloy solidify, but don't immediately cut the sprue. Watch the solidified puddle on the top of the mold blocks and in a few moments after the alloy has solidified its color will suddenly change and become duller and slightly more grey. This is when to cut the sprue. If you cut it too soon, even though the alloy looks like it had turned into a solid, there will still be some metal in solution that has not transitioned fully into a solid state.

[Ia.redneck]

You got some really good info here. CharGar has the ultimate solution, and fc60's method works very well if your sprue plate doesn't cut clean.

[Shopdog]

I mill bases on some rigs... started on a Bridgeport but quickly moved to a much simpler setup. One not so small reason is the BP is a money making pce of equipment that isn't well suited...

But that's not the reason for the post. Best I can put into words is; The cheaper the sprue plate,the more variation you're gonna have. Sounds obvious... there's folks who've never used anything but say a Lee. I like Lee moulds but their sprue plates aren't very good. Just sayin,you can have a really good technique and be hampered by the tools. And no, tools don't make the man... got it. Comparing a Lee to a custom sprue plate... well,good luck.

[charlie b]

Does alloy composition dictate how much gets torn out of the base?
*
Is adding a gas check more impactful than perfecting the sprue cut?

Yes and maybe.

Different alloys will cool differently. I have had little to no tearout with softer alloys such as 1:40 or 1:20. Harder alloys need to cool longer (IIRC) before cutting the sprue.

Adding a gas check does not change the idea that you have a cavity in the mold where the sprue was. That tear out section is basically lost weight, and, it is centered. For most pistol shooting it is immaterial, with or without a gas check.

What matters most is the edge of the base. It needs to be as perfect as you can get it. A gas check makes that part 'easier'. There was a discussion many years ago about protruding sprue and gas checks. There were three theories. 1) The chamber pressure would press the check and 'flatten the sprue, 2) the chamber pressure would force the gas check to deform around the sprue (create a dimple in the gas check), or 3) the gas check would tilt, giving a flyer. I don't know which is true.

I am only picky about my rifle bullets. I strive for small groups so any discrepancy means rejection. I have also 'shaved' off a protruding sprue in the past. Since I have gone to better molds I rarely have a problem with it.

[Wolfmanjack]

The mold I’m using is a BACO 530gr paper patch steel mold single cavity. The sprue plate is a little loose on this particular mold, I’ll tighten it up a bit and see if that helps. I wait till after the color change and then some but the tear out was never consistent with varying waiting times.