Voids inside Bullets. [Archive] - Glock Talk

PDA

View Full Version : Voids inside Bullets.


Colorado4Wheel
08-21-2011, 13:36
I have started to have problems with my bullets “keyholing”. I thought some were slightly undersized because they sized easily. So I was drilling some holes through the base of the bullets to try and make the molds a little bigger when I noticed that I was hitting some voids. At least that’s how it felt. So I filed a bullet in half and sure enough, small void near the middle. When I cast I seem to need to be at 800F to get good fill out on my Lyman 4 cavity 147gr 9mm molds. I cast using two at the same time. I think it may because I sometimes get a pretty slow pour from my Lee pot near the end. Sometimes I forget to open the adjuster on the valve a little more as the pot goes down as well. Both result in the occasional slow fill of the mold. Besides that these bullets look good. Any other ideas? This new batch is range scrap. Not WW.

freakshow10mm
08-21-2011, 16:59
I would add tin to help fill the mold out. I usually add just 2% (by weight) tin to range scrap, since it's more towards the pure lead spectrum. Doesn't add much hardness, but tin helps fill more consistently.

800F seems high for this application. Unless I'm casting 20ga slugs or BP round balls, I keep it 650-675F.

Three-Five-Seven
08-21-2011, 17:02
There should be a SUBSTANTIAL amount of sprue on top of the plate before you cut it. The sprue acts as a reservoir to deliver lead to the bullet as it cools. Additionally, if you're not getting frosted bullets, you're not at a high enough temperature. While frosting on bullets is not the goal, it is the only indicator of how hot the mold and lead is, and therefore how fast you should be working.

I find range scrap to be hard, relative to the bullet I'm aiming for. A good supply of pure lead on hand is essential when working with range scrap in my experience. More tin and antimony requires more heat and they solidify differently than pure lead or a normal, 20/1 or 30/1 alloy. I have never found a reason to add antimony to lead for casting, but you can be sure range scrap has a substantial amount in it.

So....

1. Get a significant sprue on top of the plate before moving to the next hole.
2. Raise your temp.
3. "Soften" your alloy with pure lead. (I mix range and pure 50/50 when making regular bullets and don't use any range scrap at all when making precision bullets).

WiskyT
08-21-2011, 17:06
I don't know about voids. Tin like Freak said aids fillout so it certainly wouldn't hurt.

I don't think voids are casuing your keyholing. RS is softer than WW. That will definately cause keyholing. Harden your bullets, lower your charge, or use a slower powder. Someday you'll try Unique and then your cast bullet loading will be much easier. When you do, I won't say "I told you so", but I'm sure Jack will.

Colorado4Wheel
08-21-2011, 17:28
I should add that the Keyholing is just about 1 in 25 bullets. Not every shot.

I think the keyholing is due to some undersized bullets. I was just surprised to see a void.

WiskyT
08-21-2011, 17:31
I should add that the Keyholing is just about 1 in 25 bullets. Not every shot.

I think the keyholing is due to some undersized bullets. I was just surprised to see a void.

A softer bullet will mic smaller than a harder bullet if you don't run the mic loose. If the edges of the lube band etc are sharp, they are probably big enough.

Try a slower powder. I tell you that to save you grief.

DoctaGlockta
08-21-2011, 17:34
A softer bullet will mic smaller than a harder bullet if you don't run the mic loose. If the edges of the lube band etc are sharp, they are probably big enough.

Try a slower powder. I tell you that to save you grief.

UNIQUE. It's not just for Great Grandad anymore.

Colorado4Wheel
08-21-2011, 19:17
A softer bullet will mic smaller than a harder bullet if you don't run the mic loose. If the edges of the lube band etc are sharp, they are probably big enough.

Try a slower powder. I tell you that to save you grief.

Up until my last batch everything was fine. I think I was just getting good fill out in the mold. Unique isn't going to solve that is it?

Zombie Steve
08-21-2011, 19:25
Throw a big pile of Unique in the pot when you're fluxing. You don't need eyebrows, really.

ron59
08-21-2011, 20:30
Throw a big pile of Unique in the pot when you're fluxing. You don't need eyebrows, really.

You seem to be getting funnier and funnier.

:rofl::rofl:

DoctaGlockta
08-21-2011, 20:35
Throw a big pile of Unique in the pot when you're fluxing. You don't need eyebrows, really.

You are on fire today Steve.

GioaJack
08-21-2011, 20:53
Voids are caused by several factors and each one has to be addressed individually. In no order of importance some of the reasons are;

Allowing the alloy in the furnace to get too low which decreases the velocity of the pour. It's a pretty good idea to never let the level drop below a third full.

Insufficient fluxing will allow your tin and antimony to float in suspension resulting in an abnormally high concentration of lead during the pour. The first indication of this is rounded edges on driving bands but can also result in voids.

Cutting off pour before a sufficient sprue has formed but with good flow velocity heavy sprue is not as important.

Tilting the mould during pour can easily result in voids and usually occurs as a result of fatigue.

A loose sprue plate will allow base finning which results in voids.

Knocking off the sprue before fully hardened will actually pull alloy out of the base of the bullet which leaves a void.

Pouring directly down the middle of the sprue plate hole can cause an air void in the bullet. Pouring slightly off-center allows the alloy to swirl as it fills the mould and ensures that all air is forced out of the cavity.

Clogged vent lines in the mould face can cause voids as well as finning. Clean mould face with 000 steel wool to keep lines clear.

I really don't see why you need to pour at 800 degrees with an iron mould but if it works for you then I guess that's the way to do it. I never pour higher than 700 degrees. (Have no idea about aluminum moulds.)


Jack

freakshow10mm
08-21-2011, 21:12
Jack, aluminum conducts heat better than iron, so the heat transfer is more consistent with aluminum than iron.

fredj338
08-21-2011, 23:45
Jack has some good points, but holes in the base are not the same as internal voids. Sometimes it's just technique w/ that alloy/mold, sometimes it's just bad luck. The only way to find the bullets w/ a void is weigh them. None of my cast bullets, even the really big ones, vary more than 1%. So anything greater than that, probably has an internal void & goes back to the pot. The only ones I do this with are hunting bullets or bullets used for longer range work.
Adding tin to any lesser alloy will help as the tin makes the alloy flow better. Range scrap can & is often anything. I find at my range, it's on the softer side, about what I get if I mix clip ww w/ pure lead & I treat it as such. So I tend to pressure cast, especially smaller bullets. It seems to help mold fill-out. I rarely get casting temps above 750deg w/ any alloy, even 25-1 lead/tin for LHP runs fine @ 750deg.

Colorado4Wheel
08-22-2011, 06:59
Jack,

I am using steal Lyman Molds. I think its a combination of

Letting the lead pour straight into mold. I used to let it hit the sprue plate a little. I was being lazy.
Vent lines could be cleaned.
Casting with molds too cold.

First and last ones are the most important i think.

Tpro
08-22-2011, 13:12
Throw a big pile of Unique in the pot when you're fluxing. You don't need eyebrows, really.

This ^^COULD^^ help but if it was me, and I was looking for the full effect I would use Tite Group.

That should get it done, including eyelashes:wavey:

Colorado4Wheel
08-22-2011, 14:07
Voids are in the nose not the base.

WiskyT
08-22-2011, 14:51
Up until my last batch everything was fine. I think I was just getting good fill out in the mold. Unique isn't going to solve that is it?

Is Unique going to solve your barking up the wrong tree? No.

fredj338
08-22-2011, 17:34
Voids are in the nose not the base.

FLux more often, try pressure casting. A small amount of tin wouldn't hurt, say 1/2%-1%.:dunno:

Colorado4Wheel
08-22-2011, 17:40
I have a temp gauge and I measured the temp of the mold. Basically, the mold was not getting hot enough because I am casting with two molds. I used a hot plate and cast faster. That seems to have solved the issue. Better fill out. Better sizing. More consistent weight. I still need to clean the vent lines but it's far better now.