Getting bubble/dimple at tip of point with Mihec hp mold

[gefiltephish]

Last weekend I received my Mihec 452/200 HP mold, and was ecstatic when it produced shoot-able boolits from the very first drop. I haven't had the opportunity to shoot any yet though, maybe tomorrow.

I prepped the mold by cleaning in Coleman gas. Used fine emery to lightly debur the sprue plate. Placed a smidgen of never-seize on the sprue plate pivot (I don't have any bullplate yet). Placed a tiny drop of Javelina on the alignment pins. The hp "pins" were a bit sticky, so I briefly touched the Javelina to the shafts at the outside of the hot mold. This worked like a charm and I have not seen any evidence of migration to the interior of the mold. Before casting, I preheated the mold on a hot plate. Measuring with an infrared thermometer at an angle to the sprue plate, I found that 200-215 degrees F worked out to be about right to start from. 300 degrees produced craters in the bullet base. Once I allowed the mold to cool a bit, the sprue cuts clean. I'm using a Lee 20lb bottom pour set at 7 1/2 on the dial. I don't have a submersion thermometer so I don't know the actual temp.

This morning, I just happened to be looking over some of those boolits under a lighted magnifier. First I noticed a dimple at the base of the "point" or hollow, just like you'll typically see in the sprue. After examining a small handful in which some had this and some did not, I came across one that not only had the dimple but also a cavern, as if an air bubble had become trapped during casting.

I use a 50/50 mix of range lead and WW.

What might cause this? What can I do to eliminate this? Add tin? The rest of the boolit is well formed, and produce .453-.454. Higher/lower pot temp/mold temp? I don't shoot competition so, should I not be concerned? My use is target practice and backup home defense, if I should run out of Gold Dots.

BTW, of the 30 or so I had weighed, most were in the upper 204/lower 205 range, with a few upper 203's. I'll make a closer, more careful examination tomorrow, but I expect to find most if not all those in the 203's to have the "bubble".

[GP100man]

I say shoot em , there still in the 3% of total weight .

Or seperate em & compare groups , if i get good bands & base they fly alrite.

My exp with 357 & 44 .

[Glen]

+1 to that -- shoot them and see how they group for you. As for the cause, it could be that your HP pin was not quite hot enough. Keep the pin in the hot bullet metal and hot mould blocks as much as possible. Also, does your HP pin have a flat tip? Or a rounded or pointed tip? A flat tip will commonly lead to defects at the base of the cavity as well.

[lwknight]

Craters in the base of the boolit mean that the mold is hotter than the sprue plate and might be casting a bit hot. make bigger puddles on top to heat up the plate so it will stay liquid till the boolit solidifies totally.
Craters in the boolit indicate mold contamination, possibly migration of lube.

[Crash_Corrigan]

Ditto on what was said above. Make a nice full sprue on top of the sprue plate and did you notice as some molton alloy is sucked into the cavity from beneath?

It should leave a little dimple in the sprue. Once the color of the sprue changes it is time for twist that sucker off and decant some boolits. If you wait too long the sprue gets too hard and you will have a hard time.

Use of Bullshop Bullplate Sprue Plate Lube on top of the mold, pins and pivoting screws and the underside of the sprue plate will allow you to cast faster and easier.

Once you see that dimple in the sprue pile open up that mold and dump those boolits into cold water. Even though the alloy will still be soft and almost liquid it will not stick to the sprue nor the top of the mold and the sprue will open with a gloved hand. No need for a hickory hammer handle to whack at your molds.

For further guideance I whole heartedly recommend the world famous "Bruce B's"
'Method' which is available free of charge by use of the search engine within this forum.

May the silver stream etc.

[mooman76]

Are you preheating your hp pin as well? That can cause it. Personally I would shoot as is if it's really small and hard to see. It doesn't matter as much in a pistol as it does a rifle bullet unless you are shooting at long distance.

[Dale53]

The trick to good hollow points is to keep the pins hot. This means casting at slightly elevated temperatures (25-50 degrees hotter than for a non-hollow point mould) and minimizing the time that the mould is open between casts. Get into a rhythm and don't stop until you are finished.

Study your operating method with the Cramer style mould and work to minimize the steps from pour to pour. The idea is to maintain hot temperatures of the pins, so that you get good fill-out around the hollow point pin.

FWIW
Dale53

[GP100man]

G

You are talkin about in the bottom of the HP cavity , just to clarify??

But yes a cold pin will cause a little void at the base of the cavity .

It`s a balance of keepin the pin hot enuff , fill speed & actual castin speed!!

When my pot is full (10#) ! have to slow the flow or I`ll get voids in driving bands towards the front.

But think in weight % instead of actual grs.

Reread post again & I`ll bet some of that never seize is migrating under hi heat!!

[jbc]

to clarify - I think this is a cramer style hollow point mold - the pin does not come out, there are two pins on shafts that come out of one mold half so keeping the pin hot is not a problem - they stay the same temp as the mold

[gefiltephish]

to clarify - I think this is a cramer style hollow point mold - the pin does not come out, there are two pins on shafts that come out of one mold half so keeping the pin hot is not a problem - they stay the same temp as the mold

Yes, it's a Cramer style mold. I forgot to mention that. I'm using the hex pins that have a flat on the tip of the pin. I figured the pins would stay pretty much the same temp as the mold. I had cast about 300 bullets, and I thought I had a nice steady rhythm going. I don't think I can cast much faster then I was already, but next time I'll see if I can refine my procedure a bit.

I pour, in a few seconds I cut the sprue and open the mold. Push or gently tap the pins (plastic mallet) to drop the bullets, but sometimes I have to tap on the mold gently to get one of the bullets to drop. Push the pins back in. Close the mold and swing the sprue plate around. Start pouring. The mold doesn't get much time to cool. It took much longer to write this paragraph than the actually procedure.

Next casting session I'll pay more attention to which cavity the bullets come from and separate them into 2 piles. This way I'll see which cavity/pin has the problem, if it's only one of them.

GP100man
If the never seize was the problem, I would think it would reveal itself first in the base, lube groove etc and the pin last, if at all. I intend to get some bullplate lube when I can, but for now this is all I have. Well, I do have some Franklin mold release that I was thinking of spraying to the bottom of the sprue plate in the mean time. (After trying this stuff on Lee molds, I will never use it inside a mold again.)

I'm wondering if this is one of those situations where ladle pouring may work better than bottom pour? Only one way to find out for sure, eh?!

Thanks to everyone for your input!

[lwknight]

Maybe you got some lube on your pin causing the pocket?
I got the bright idea to put some lube on my hp pin and it did not help one bit. I finally figured out to use softer alloy and it comes off easier.

[gefiltephish]

No lube on the pin. If lube in the works was the cause, then I expect every bullet would show the problem, not just some. However, as I indicated in my last post, I do not yet know if the issue is with just one cavity or random. We shall see.

I have thought about applying mold release just on the pin for an easier drop. I'd rather not tap on the mold if I don't have to, even if it is only lightly on the head of the mold handle screw.

[gefiltephish]

G
You are talkin about in the bottom of the HP cavity , just to clarify??


That's correct. Just for the record, I don't consider this to be a major issue, but if it can be solved easily, why not?

[GP100man]

G

Spraying the sprue plate with mold release may cause it to create a seal & trap air .

Don`t ask how I know this LOL!!!!

I agree that the cramer style should hold the pins heat up .

Turn up the alloy temp & fill the cavitys slower??? giving air a little more time to vent???

[Dale53]

gefiltiphish;
I have limited experience with the Cramer style hollow points (that will shortly be resolved when Miha starts shipping the #503 Cramer style mould, hopefully).

At any rate, I have used one, and I see absolutely NO problem with using a light coat of Mould Release on the heads of the pins for easy release. I use Rapine mold release, which consists of microfine graphite suspended in De-natured alcohol. A light coat of that on the pins should certainly allow easy release. It is recommended that you let it dry several hours before use. On occasion, I have had to use it shortly after application and it seemed to work fine...

FWIW
Dale53

[gefiltephish]

Here's an update. Cleaned the molds thoroughly with denatured alcohol. Sprayed mold release on the pins, bottom of sprue plate and top of mold (with bullets in cavities). Went over the pin shafts with fine emery so that I could slide them with a gloved finger and no lube.

I'm about out of ww's so I decided to just use range lead. I don't plan on shooting these. I figured that this could be like comparing apples to oranges, but I plodded onward.

Preheated the mold on hotplate while pot is coming to temp. This certainly baked the coat of mold release before pouring. Overall, the bullets looked like hell, but being able to push the pins in and out with a finger worked out great 'cause it made it easier to keep them separated. They dropped right off the pins as well, no more tapping on the mold. Those that did stick a bit just required the mold handles to be snapped open once or twice and they fell right off.

I began adding a couple of feet at a time of 50/50 tin solder to the pot to see if fill out would improve, which it did. Eventually a pattern had emerged regarding the crater in the pin hole. All the bad came from the nearest cavity. Several burned fingers later, I had switched the pins to the opposite cavity. Not surprisingly, the craters were now appearing from the far cavity.

I wonder what could be different about one pin? As they come from Mihec, they have what appears to be a black oxide finish. Could that be having some effect, and if so, why only one of the pins? Besides, both pins are now coated with mold release, so... Well, I'll pull the offending pin out and clean it in acetone and recoat with mold release. I can also try the round pins in place of the "bad" hex pin.

<edit>Forgot to mention that I changed the pot setting from 7 1/2 to 8. Next I'm going to try 7 just to see what happens.</edit>

To be continued...

[JesterGrin_1]

Ok here is a tip that I think will cure your problem. :)

Do NOT pour from the bottom spout of your melting pot directly in the center of the sprue plate hole. Have the stream of lead just inside of the cone of the sprue and let the lead swirl in. It works lol.

[gefiltephish]

Nope. I always do it that way, never pour straight in, unless accidental. I did try ladle pouring as well, but there was no improvement. I also tried speeding up and slowing down the bottom pour without significant change.
-------------------
After setting the pot to 7, later I bumped up to 8 1/2. Even at that high setting and going as fast as I could, I was surprised I couldn't get any frosted bullets.

Last I tried swapping one of the hex pins for a round pin. Not a single crater with the round pin. AND, this bullet dropped right off the pin as soon as the mold was opened. No mold release used. I made 33 with the round pin, which gave a 2 grain spread and average weight of 202.38.

Even after adding 1lb of solder (thought I had 50/50 but it was 60/40) to 16lbs of range lead, fill out in the lube groove area was not very good, regardless of temp and speed. I'll smelt some ww's tomorrow and pick up some tin (I hope).

[Tippet]

interesting thread, and I was about to mention the same thing about indirect pour.
I'm curious to hear back what happens after you do what you're doing to the "offending" pin.

[JesterGrin_1]

Tippet it took me HUNDREDS of bad Boolits to figure out to do an indirect pour lol. Plus since his molds are Brass they have to be HOT. I cast right at about 825F.