Consistency applied.

[MBTcustom]

One thought on the serious side, the 168 Sierria and it's other variant normally employ a small hollowpoint to produce a blanket of air to assist with the surface friction in the air, much like a boat hull in the water, wonder if the same would work for cast.

It does. My Accurate XCB bullet design (31-160G, cast by me, and HPed by me) was tested with and without a precision hollow point by Larry Gibson, and there was a positive measurable effect to the bullets modified to HP.

[kbstenberg]

Tim I think I am understanding the relation of bell curve and dertermining the better heat setting.
Is your second step in better casting.Then using one temp. bell curve the different time sequences in the casting process.
Am I correct in assuming the different timed periods in your casting system are.
A. Time taken for the sprue to solidify. (At what point in the solidification process do you cut the sprue?)
B. Time between the bullets are dropped and the mold is closed.
C. How long between closing the mold, and refilling it. I think that is what you call lag time.
I have learned that the timing of closing the SP has some bearing on how much heat is held in the mold.
My son made an app for the comp. to show continuous timing. So I have started using that rather than counting in my head.
The particular mold I am using doesn't let the sprue puddle stay in the molten state for more than a second before it freezes. I have taken the mold to a temp. of 400 and all bullets are to a heave frosting. At 390 deg. mold temp. the bullets come out 3/4 frosted. My pot temp is 720 deg. my alloy is COWW+ 2%sn.
If I tried using a melt temp. of say 730 to try to get a longer sprue liquidus state. And used a much longer time periods to offset the hotter melt temperature to keep the mold temp. down. Would you consider those changes to get your longer sprue liquidus times?

[MBTcustom]

Tim I think I am understanding the relation of bell curve and dertermining the better heat setting.
Is your second step in better casting.Then using one temp. bell curve the different time sequences in the casting process.
Am I correct in assuming the different timed periods in your casting system are.
A. Time taken for the sprue to solidify. (At what point in the solidification process do you cut the sprue?)
B. Time between the bullets are dropped and the mold is closed.
C. How long between closing the mold, and refilling it. I think that is what you call lag time.
I have learned that the timing of closing the SP has some bearing on how much heat is held in the mold.
My son made an app for the comp. to show continuous timing. So I have started using that rather than counting in my head.
The particular mold I am using doesn't let the sprue puddle stay in the molten state for more than a second before it freezes. I have taken the mold to a temp. of 400 and all bullets are to a heave frosting. At 390 deg. mold temp. the bullets come out 3/4 frosted. My pot temp is 720 deg. my alloy is COWW+ 2%sn.
If I tried using a melt temp. of say 730 to try to get a longer sprue liquidus state. And used a much longer time periods to offset the hotter melt temperature to keep the mold temp. down. Would you consider those changes to get your longer sprue liquidus times?

First, do not count in your head. If you check yourself against a clock, you will notice that you either count too fast, or too slow throughout a casting session. You need to use something that is more consistent.

Also, do not time each stage of the casting operation only (fill, cut, drop, close, dwell, refill, etc etc etc.) You need to be consistent in the total time it takes to complete all these tasks, regardless of whether you get a bullet stuck in a cavity, have to scratch your nose, drop your stick, lube your mold, leg breaks off your chair...... etc etc etc.

If you utilize this system and keep a completely open mind, you may find the most consistent point gives you plenty of freedom to time the entire cycle and it may be something you never would have figured on.
I watch the clock, and when I'm dialed in, the sprue plate opens at the same time @ 3 seconds, the bullets drop at the same time @ 5 seconds, (I allow myself time to look in the mold and check it for lead spatter (about 3 seconds)) and the mold is shut again @ 15 seconds.
How long I wait after shutting the mold is completely a function of the alloy/mold temperature relationship, and is set by the bell curves. When I'm casting with a mold, the mold is the boss, and it doesn't care what I or anybody on this forum thinks is right or wrong. I am not in charge of the casting operation, the mold is. I just work here.

I can tell you this, when I'm using an alloy similar to yours, with a certain brass two cavity mold, the pot temperature is set at 695 degrees, the mold is run at 450 degrees, and the entire cycle time from pour to pour is 30 seconds. That's what the mold likes. I never would have run at that cadence and temperature listening to the advice of other people, and that is not the same for all my molds. I would like to think that another brass mold of similar caliber and bullet weight, block size, and SP size, would run in a similar fashion, but I really won't even try to assume that it would. The bell curves will tell me soon enough what the exact combination should be.


Just watch your bell curves and try different things. It really doesn't take long to run several batches of 100 bullets in order to dial in a casting prescription, and you're getting lots of good practice like dry firing a target rifle in your living room to get trigger time.
Use a logical thought process, and constantly observe what you are doing. I time the entire cycle above all else, because I noticed I was dealing with this phenomenon that we all know and love called "tolerance stacking". I was trying to time each task precisely, and what I found was that my overall cycle time was varying wildly by as much as 10-15 seconds. I was working my tail off trying to micromanage the hell out of my operation, and I was only fooling myself.

Does that help, or did I misunderstand your question?

[kbstenberg]

Sorry about my thought and writing pattern.
Yes you answered my timing question completely. I thought each stage of casting was timing controlled.
With my mold producing heavy frosted bullets at 395. I am assuming that would be the hottest I should run it. Even though my sprue puddles don't stay liquidus for more than 1+ seconds? (let the mold tell you what it likes.)
I did up the melt temp. to 725 and got very little more additional time with the sprue puddle. But my bullet weight variation increased dramatically Kevin

[RogerDat]

Well thanks for the information and ideas!
If I can't measure in a manner that provides some guidance on what to change and a method for evaluation of the effect of that change then I'm just guessing.

I punch paper for fun, guess you could even say I shoot rocks but I have learned a couple of things over the years. Practice only makes perfect if you practice doing it perfect. Once a physical operation becomes very well practiced even done "casually" it is done more consistently.

Be it welding, driving a golf ball, or using power tools once you have developed a good technique even just taking a "whack" at doing it quick and dirty you will use that good technique and yield better results. Now I have to add a digital scale to my wish list but look forward to knowing the cast part of my effort is consistent, then I can more effectively gauge the difference powder load/type makes.

Just because I'm only shooting paper plates don't mean I want to miss.

[MBTcustom]

Paper plates are awesome. I've shot them for years with a 1" dot in the middle made with a sharpy marker. Give me a pack of paper plates, a marker and a staple gun, an I've got targets a-plenty.

A digital scale is a wonderful thing, and I have become quite fond of the Frankford arsenal model. IIRC they are on sale and (gasp) in stock at MidwayUSA right now.

The main problem with controlling your process, is that just controlling it will only get you so far. You have to find out how to do things "exactly" right, or you will be doing things "exactly" wrong.
It's the old "accuracy vs. precision" principle. You need both.
When I first started casting, I was neither accurate nor precise in my method. I started trying to improve myself, and only got so far because while I improved accuracy, I still lacked precision (one does not equal the other in front of a casting pot). So I was being a total control freak with my process, but I still had a broad bell curve.
This method, will take you from a point of precision with no accuracy, to a place where both shake hands to give you a nearly perfect casting prescription, and very impressive bell curves.
See this explanation of scientific accuracy vs. precision:

http://celebrating200years.noaa.gov/...precision.html

[MBTcustom]

Just an update, I now have an RCBS ProMelt casting pot given to me by a very kind forum member who I am building a rifle for.
I haven't been able to really rag it out yet, although Lars45 and I got to play with it a little last Sunday. Given the excellent design of this pot and the apparent uniformity of the spout, I think this may take my pursuit of consistency to the next level. I'll post when I have a chance to rag out his awesome new piece of equipment.

[SgtDog0311]

I'm not a high velocity shooter but still find this thread very interesting. I frequently, if not always, do a bell curve of my casting sessions just to see how I'm doing with my mold and casting technique, and as a method for further cull. More time than most would spend but there it is; I've only been casting a few years so lots to learn!!

If I ever get to plus or minus .02 I'd consider myself "accomplished". Most my caliber/curves will be anywhere from .07 spread to 1.5 spread. Size of the bullet makes me use a longer piece of tape Even with a single cavity I've not made any skyscrapers.

So, I'm not posting the pic to brag (obviously) but to illustrate advice Green Lizzard gave me once concerning two cavity molds. The point is made pretty well here and that is: if you don't mark cavities when two cavity molds drop different weights will pose a problem where the curve from each overlap.

How do you know when a bullet from the heavier cavity drops down into the range of your lighter cavity if they are not marked somehow? This illustrates the problem fairly well. Looks like my cavities drop about .07 of a grain difference in weight (numbers would be pretty equal except 50 from the lighter cavity are being pan lubed).

Then again, maybe the cavities are equal and my technique actually sucks that bad Regardless I'll shoot all but the outside two columns and treat these as two .5gr-.6gr spreads.

[Sticky]

I need to mark my molds as you mentioned John. I have all multi cavity molds, most are 4 cav, a couple of 2 cav for rifle boolits, but I am sure that this is causing me some variance in my curves due to the individual variances from cavity to cavity.

I have been working with my mold and alloy temps, learning to time myself and it is helping (though I still have a LOT to learn) with better consistency in my casting sessions. I am getting much closer to a consistent +/- 0.5gr, want to get it down a couple tenths on either end, but with multi cav molds, I do have some challenges to face. Live and learn.. LOL

This thread has been helping me immensely! Thanks goodsteel!!

[Blackwater]

This thread really needs a sticky on it. Administrators?

[popper]

Cast a bunch of the 31-142C plain base - 2C Al. this morning, @ 700f, same alloy as before when I tried 720 & 680F. 21 culls of 108, 3 were bad pours (me, no real base), 2 had the bad drive band spot, the rest were just slightly rounded base. Then I tried leaving the mould & plate open longer ( a really fast count of 8) - 15 of 80 culls. 4 bad pours, 1 bad drive band and the rest rounded base. BUT - sprue cuts were really hard with gloved hand and sprue cooled faster than the base so base dimple was huge. All were still frosty in the middle. I did find 'dragging' from one to the other cavity gave poorer results, same as I found for the slotted plate. No 'purging' of the spout, no bad noses. I 'broke' the top edge of the mould last week to help venting, only the pivot side cavity seems to throw the bad spot now. Still have to figure out why I get so many rounded bases but i insect pretty good no no real big deal. No I don't plan on weighing them. Last batch did 1 1/2" @ 100, 1750 fps. Will sorting make a difference @ 2-300, possibly.

[David2011]

When I wrote this I was at the end of page 4 of 8. This has to be the best single thread on casting I've ever read. I've been casting since the early '80s and still learn constantly. The contributions here are from the people I consider the rock stars of CastBoolits. I know Tim is a first class act.

Casting tonight, I stumbled across something new to me. I've always poured with a generous stream out of a bottom pour RCBS Pro-Melt. I was trying to empty the pot to clean the rod and spout. The lower the lead got the smaller the stream got and the better my boolits got. The mold temp was easier to control and even though it took longer to fill each 158 grain cavity, the pace went up because the mold wasn't getting as hot. I have to try restricting the flow with a full pot to make sure there wasn't something going on with the melt temperature before making too many conclusions but the slower pour seemed to make much better boolits. The wait between refills was reduced to literally nothing. I was using a 6 cavity Lee .38 mold which I find much more difficult to use than Lyman, RCBS and SAECO iron or leaded steel molds. Production was so much better with the small stream I couldn't believe it.

Thanks for the great thread, Tim

David

[MBTcustom]

You're welcome David, but just remember, every mold is different with different preferences, and spout flow is another thing that has a sweet spot.
I just got an RCBS Promelt compliments of Jayvod, and I'm still getting used to it. My little Lee 4-20 was very consistent in pour from 3/4 full to 1/2 full, and I have no doubt the RCBS will be the same. There's just no way around it.
However, the RCBS just seems to have a lot more pressure on the stream. I can adjust it down, but then, I'm not filling the cavities very fast.
I'm still playing with it. I only cast on Sundays, and last Sunday I put a Lee two cavity 500 S&W mold through it's paces. That, my friend, is a beer keg of a bullet! Since it was for a friend's handgun, all I was concerned with was physical appearance on the first batch.
The first run was pretty rough with a 30 second cycle time. I think that little Lee mold had more lead in it than aluminum after it was filled! I dumped all the bullets back in the pot and cast again, but this time with a 1 minute cycle time. That made good looking bullets.
This Sunday, I'm going back in and I will start plotting bell curves with the bullets and see where and exactly how the mold likes to run.
Honestly though, this ProMelt was a veritable atomic bomb to my process (even though it's all that and a bag of chips!). I'm hoping that all the dope I figured out for my molds with the Lee pot is still good for the ProMelt!

[popper]

Cast 10# of 9mm RNFP BB tonite, 4C Al. mould. Had the same problem of poor base fillout, frosty rounded base, running at 700F. Slowed the pour stream down to just more than a trickle and problem went away. I could actually watch the cavity fill and the puddle form. Alloy is more fluid at higher temperature, flows faster! Pouring too fast and the sprue puddle fills - plugging up flow AND/OR cutting off the venting under the plate. When casting the 140 30 cal I noticed bases were worse at high temp but weight consistency (of good ones) was better (720 vs 680). I modded the Lee pot with a tap handle on the stem and had only poured the 140s since. Problem solved. Lower temp of 680 made the sprue cut very hard to time & IMHO gave tilted cuts so more weight variance.

[popper]

Cleaned the pot, adjusted the spout and poured ~850 for the BO with Isocore I ingoted yesterday. 700F - 53 culls, mostly slightly rounded base. 11% culled, 2 with the bad rear band, several incomplete bases - my fault. Cuts were clean with no pimples or divits. For the weight & clock watchers, I weighed ~ 50. 1 -140, 9 - 139.4-5, most were 139.7-8. Tossed one at 139.0. I'll try 710 next time as the sprue cooled fast. Puddle only filled the bevel.
Time to take a nap after cutting a bunch of live oak branches that were overhanging.

[popper]

Poured a bunch more for the BO. @ 710F, 17 bad, one was me, reject rate way down now . Weighed some good and bad (slight rounded base, divit in drive band, etc.) Same spread as before - for good and bad. Sprue cuts were great on all. Big HiTek session coming up.
Edit: For this mould ( & alloy) I found the temp sweet spot - 710F. 700 & 720 gave bad bases. Pour rate was just as sensitive - too slow, smiley faces, too fast - bad bases. I don't watch the clock but do watch the sprue and pay attention to the cut - whatever makes the 'cut' just right. Gone from 50% rejects to 4% for this mould.

[fivefang]

Hi & thank you Larry & Tim both for the fine information,but we all must stay aware of that some of us drive 25 yr. old pickups ,while others do not, so,the $ aspect comes in!shoot what metal you can afford,& learn all you can from those that have the $ means to teach, many thank for your time & efforts,now for tc 9w. gc's

[MBTcustom]

I love this thread. Rarely have I given so much information in one spot. I feel I have explained my position as thoroughly as my vocabulary will allow me to, and those that are looking to advance have easy access to clearly written information.
There is nothing else I can add without being redundant. I hope it helps people get where they are trying to go.

[Maximumbob54]

I would just like to thank Goodsteel and all that positively added to this thread. I tried a couple of the suggested changes last night in a short batch. I cast a lot of bulk blasting bullets from 6 cavity Lee molds and I usually see tearing from the sprue. It doesn't bother me much as they are just for 25 yards and in blasting fun but it wouldn't hurt any for them to be made better. Just slowing down and watching the clock to set the rhythm of the casting I hardly tore any of the bases. I have a small stash of Roto Metals and MBC ingots set aside for an upcoming project. The notes I've written down will all go into effect once I start using the "excellent alloy" but even the range scrap blasting will start seeing these improvements. Thanks to all!!!

[Chris C]

WHEW!!!!! goodsteel, you and sgt. mike have my brain buzzing. SgtDog0311 turned me on to the bell curve concept a couple of years ago. I've just started casting (yesterday in fact) but have used it over the years sorting commercial bullets for my target work. However, I don't have a digital grain scale and had been sorting them with a digital gram scale. When I cast my first 145 bullets yesterday, I was very pleased with how many weighed the same. 85 weighed 15.9 grm and 39 weighed 16 grm. But curiosity got the best of me today and I sat down at my beam scale and weighed them out............laboriously, one by one. Very disappointing............but probably typical for a beginner. I only had 22 that had the same weight, and there were no more to add within the +or- .1 gr range. Their weight varied from 243.3 gr to 247.9 gr. The largest number were 246.6 gr. So guess I can quit patting myself on the back. Obviously, I've a lot to learn about consistency. Thanks for starting the thread and for all who have continued it. Whew! Lot's to learn on my part.