Casting Test - Bullet Bases ... If You Have a Black Ring, Your Casting Wrong!

[John Boy]

Today I was studious and payed attention to my bullet bases more than I every have. This is not to say I can't cast good bases but here is an observation and the answer for discussion:
* Sharp bases have no 'black ring' around them when the sprue is cut
* Beveled bases will have a 'black ring' around them when the sprue is cut
I deduced the no and with ring to one important casting step ...
What do you believe causes the base of bullets to have a 'black ring' when the sprue is cut?

[VHoward]

Do you have a picture of this black ring? Don't know if I have ever seen it.

[Bullshop]

Black ring means you cut the sprue with an acetylene torch. Always happens to me when I do that.
Patient, Doc it hurts when I do this! Doc, well then don't do that!

[swheeler]

The black ring means you are casting too cold, way too cold, it's frostbite and needs to be amputated.

[btroj]

Incomplete fill is often caused by a too small sprue in my experience. It tells me I quit pouring too soon.

I can easily tell bullets that have rounded bases when I open the mould.

[swheeler]

Incomplete fill is often caused by a too small sprue in my experience. It tells me I quit pouring too soon.

I can easily tell bullets that have rounded bases when I open the mould.

Are they black?

[ubetcha]

I can see the effect a rounded base on a plain base bullet causing accuracy concerns, but on a gascheck design,would it matter? If one looks at an installed gascheck,the edge is rounded.

[Dan Cash]

I can see the effect a rounded base on a plain base bullet causing accuracy concerns, but on a gascheck design,would it matter? If one looks at an installed gascheck,the edge is rounded.

Rounded bullet bases are seldom uniform which causes the accuracy problem.

[swheeler]

I guess I'm missing something, what BLACK ring? I thought it was a joke?

[725]

Could it be that the "black ring" is just where the light is casting a shadow while the boolit, with an incomplete fill out, is still in the mold? When the boolit drops free, is the black ring still there on the boolit?

[JonB_in_Glencoe]

Black ?

[swheeler]

Ok, think I have it, if you see black on rounded bases first thing you did WRONG was to smoke the mold, second could be not large enough sprue puddle or a mold that is not venting at sprue plate(plate too tight, need to chamfer top of blocks).

[swheeler]

What say you Johnboy?

[swheeler]

I guess I failed the test, wish I could have studied:)

[John Boy]

What say you Johnboy?
OK - the black ring ... When one cuts the sprue, visually look directly down at the bullet base that is inside the mold.
* If the base of the bullet is not completely filled exactly to the top of the mold, you will visually see a black ring around the base - you have a bullet with a beveled base
* The 'black ring' is visual, caused by the bevel of the bullet base. The more visual (larger) the ring, the more that that base is beveled
* A bullet in the mold that has no visual 'black ring' is completely flush with the top of the mold - A Perfectly Filled Out Base

What causes the 'visual black ring' around the base? LACK OF HEAD PRESSURE!
If the dipper is not completely filled with lead from the pot and the spout firmly placed in the sprue hole , the gravity head pressure drop of the lead will be less during the pour, for 5 seconds, and the cavity not completely filled with the base exactly flush with the top of the mold

I played around doing this with a 2 cavity 200gr H&G68 mold. When I filled cavity #1 from a full dipper, then moved the spout to cavity #2 with half a ladle of lead for the next 5 second pour ... the pour invariably created a visual black ring around the base = beveled! So for the next bullet pour, I filled the ladle full of lead for each cavity pour = Perfect Bases

Being lazy, I took a larger ladle to pour the 2 cavities with one dip in the pot and was able to pour cavities #1 and #2 with one dip of lead and ... No Black Rings because of heavy head pressure![smilie=1:

For the good of the order ... I have been casting since the '60's and am anal about producing bullets with sharp completely filled out edges - no bevels. Primary reason - I shoot BPCR long range to 1000yds and next to obturation at long distance shooting, a perfect bullet base is key to accuarcy

And BTW, I don't create a Mt Everest sprue puddle when I pour. I spread the puddle thinly over the top the the plate to keep it consistently the same temperature. Mt Everest's are not needed IMO to obtain sharp bullet bases


Could it be that the "black ring" is just where the light is casting a shadow while the boolit, with an incomplete fill out, is still in the mold? When the boolit drops free, is the black ring still there on the boolit?
725 ... Grade A :D Drop the bullet = no shadow = bullet with a bevel

[btroj]

The ring is black because it is a shadow line. You are seeing the gap between the base of the bullet and the edge of the cavity.

[Smoke4320]

The ring is black because it is a shadow line. You are seeing the gap between the base of the bullet and the edge of the cavity.

ding ding we have a winner

[Larry Gibson]

John Boy

You're catching a lot of flak because you're making up terminology none of us are familiar with as you go along. Now that we understand what you are talking about (incomplete fill at the base) perhaps some help is in order. BTW; "head pressure" is another misnomer. If you are pressure casting with the dipper (waht make/kind of dipper?) then the answer is; yes there is not enough pressure. What you are refering to as the "head" I assume to be the "sprue"(?). When casting with a dipper with a spout on it I prefer to use the methods described by Lyman;

Hold the mold horizontal in left hand with sprue plate facing other hand/ladle.

Dip the ladle through the alloy in the pot and holding level put the spout in the sprue hole.

Turn both mould and ladle upright together filling the mould.

Lift the ladle up allowing a good sprue to un into the spue hole and form on the sprue plate.

Be generous with the sprue pour even if the alloy runs off, hold over the pot so alloy run off goes back in. You may be of the opinion it is not necessary for such a sprue (Mt Everest?) but then why the "black ring" question if not?

Fill each cavity with a fresh fill from the alloy in the pot. Seems you ahve self discovered that with bullets of 200 gr.

And now that I have thoroughly read and reread your last post I see why the term "black ring"......you are a BPCR shooter and have "black" firmly imprinted on the brain.........it can be a serious affliciton but there is hope by shooting judicious quanities of that new fad; smokeless powder[smilie=l: welcome to the world of clean shooting.........

Larry Gibson

[John Boy]

it can be a serious affliciton but there is hope by shooting judicious quanities of that new fad [smilie=l:smokeless powder welcome to the world of clean shooting......... Thanks Larry but I'll leave the new fad with the K31 and 30-30.

Clean shooting? I've gone to 75 consecutive but a friend has gone to 105 rounds with Swiss Null-B in 22LR's :D The velocities average 1130 fps over the chronograph with SD's in the 12-19 range! [smilie=1:

[JonB_in_Glencoe]

What do you believe causes the base of bullets to have a 'black ring' when the sprue is cut?
OK, now I understand, I'll play...

the answer is:
The mold not hot enough
OR
mold doesn't have adequate venting

Good Luck,
Jon

[SciFiJim]

I was thinking insufficient venting. However, you said that you do not pour a "Mount Everest" sized sprue. The sprue plate may not be hot enough and the lead is cooling before it is filling the cavity to the bottom of the sprue plate. Pouring a generous sprue will keep the plate hotter and provide extra lead for fill out and time for it to do so. If you already get the complete fill out most of the time, you are already close to what you need, just pour a little more. If you cut your sprue with a gloved thumb, you can drop the sprue into your palm and ease it back into your pot before it gets completely cold. That way there is no wasted time or energy to remelt it later.