Benefits to Pressure Casting

  • Last Post 26 December 2022
Wm Cook posted this 16 December 2022

I hijacked this from the Lee Dipper thread.  I apologize in advance if I ticked anyone off or if what I did broke any rules.  My thought was that the subject of pressure casting was not directly connected to the original post and the topic about pressure casting had a value great enough that it could stand on its own.

Bill said:

What’s the added value to pressure casting with the dipper?  Would you happen to know the bullet dropped weight with pressure vs without ladle pressure casting?

John said:

Good question. Also are the bullets more uniform in weight?  Has anybody who believes "pressure casting" helps run these simple experiments?  If pressure casting improves bullets, is using four inches of pressure (bottom pour)  better than one inch (dipper)? 


Aaron said this in the following two threads:

  • I always mate the dipper and mold and allow the melt to dwell on top of the mold bearing its full weight
  • Bullets cast in this manner are very uniform.  I either mate the mold and the dipper - or - use the spout on the  bottom of the pot
  • Most of my molds do best with the full weight of the pot over the pot spout. Some of my molds REFUSE to fill out properly with the pot spout and must be dipper cast.
  • The lead in the dipper, when mated to the mold, adds weight to the pour. All 8 oz of lead are trying to force its way into the mold improving fill-out like using a bottom spout on the melting pot with 20 pounds of molten metal on  top of the mold.
  • We know these answers from frustrated attempts to make a mold cast properly. We try pot   spout feeding with no gap, pot feeding with a small gap, modified cadence and temperatures, and eventually dipper feeding with a prescribed cadence and temperature. As I said, each mold has a personality and works best with one method or another. Of course    alloys differ among molds too and that certainly plays into the casting feeding preferences of    the molds. 

I think I parsed that accurately.  Again I apologize if anything was misrepresented.

Sidestepping the debate about weighing versus not weighting bullets for accuracy most would agree that a fully filled out mold cavity will weigh more than a cavity not properly filled out.    

To a degree I accept the cop out that "all molds are different" but not lock stock and barrel.  Aaron allows for that as a possibility but he leans heavily toward to bottom pour pressure casting or ladle pour pressure casting.  He did this based on his personal experience with casting. 

Can a general statement can be made that when starting a new mold one should at least begin with pressure casting.  Does anyone have any data they could share?  Thanks, Bill C.





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John Alexander posted this 16 December 2022


Thanks for moving this discussion.  I was as guilty as anybody in hjacking 2frogs thread but we should try to resist the temptation to go off on tangents and instead start our own thread.

On to pressure casting:  

It certainly sounds reasonable that the pressure in the pot, or dipper, should help fill out bullets. For years I used pressure casting with either a dipper or bottom spout pot and it worked OK for me on some molds but not others.  

I was always suspicious that the pressure wasn't helping much because it was so low. (0.4 #/ sq.-in. for a one inch of head in the dipper or 4.0 #/sq.-in. for 4 inch depth in a pot.)  

Since, with pressure casting there is no gap for the air in the mold to escape out the sprue , I assumed that a mold needed good venting either horizontally out of the bullet cavity or out under the sprue plate to work with that method, and maybe some of my molds didn't have good enough venting. That was my theory, but I never tested it by improving the venting on a reluctant mold to see if that cured the problem.

I saw recommendations for holding the mold about 1/2 inch from the spout of the pot and that sounded like it might help in letting the air escape out the sprue while the lead was going in when a mold had only marginal venting -- and if there was anything to my theory that venting was the problem. I tried it on a problem mold and it seemed to cure the problem. I have never pressure cast again. Letting the stream of lead fall into the mold seems to work on all my molds and seems easier and faster to me.

There is more than one way to skin a cat.



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Duane Mellenbruch posted this 16 December 2022

A consideration about starting with pressure casting in a new mold is the possibility of some oil or other debris that needs to off gas as part of the break in period.  If after a few casting sessions, I still have a mold that does not fill out consistently in one spot, then I would pressure cast to get the hot alloy pressed against that spot and get that area up to complete casting temp.  Sometimes just that intimate contact between the mold and the alloy will take care of the minor issue and  the mold will behave from that point on. 

If a sprue plate hole is too small, then pressure casting might be the only way to get hot alloy into the mold cavity.  I did have an issue with a SAECO mold. At that time, Saeco was using both a plate with large holes or small holes and the first sprue plate had small holes.  The usual sprue plate hole was nearly the same size as the base of the #221 mold which is for a .225" 60 grain gas check bullet. There was no way the broad stream of the Lee bottom pour pot would flow into the mold without blocking the air escaping from the mold. They provided an old sprue plate with the larger holes to try.  While that worked, the sprue cut was too large so the plate with the small holes was enlarged one drill bit size and the problem was resolved.

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Aaron posted this 16 December 2022

To a degree I accept the cop out that "all molds are different" but not lock stock and barrel.  Aaron allows for that as a possibility but he leans heavily toward to bottom pour pressure casting or ladle pour pressure casting.  He did this based on his personal experience with casting. 

I don't believe my statement is a "cop-out." With 64 molds on the shelf and most capable of casting with different alloys for differing purposes, molds have personalities. Some molds have multiple personalities based on alloy. Each mold is slightly different and the best than can be said is that they "behave" in groups so-to-say.

It is also important to recognize that there will be casting sessions where NOTHING works. I have had several of those over the decades and have learned to turn the pot off, cool the mold, and come back at it another day. It seems when things go wrong during a casting session, they never get better during that session.

To the ultimate question presented; which method to start with, I posit that the new mold owner cast with the tools at his or her disposal. If the results are not satisfactory, try another method and/or tools. If I were teaching a casting course, I would advocate a large dipper capable of holding a goodly amount of molten metal and pressure casting with it - or using a #20 pot and pressure cast with it. Get the bottom pour pot and have a dipper ready in case the pot does not perform well with a particular mold.

Try not to burn the wood handle off the dipper. cool



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Wm Cook posted this 16 December 2022

Sorry for the misunderstanding Aaron. 

To a degree I accept the cop out that "all molds are different" but not lock stock and barrel.  Aaron allows for that as a possibility but he leans heavily toward to bottom pour pressure casting or ladle pour pressure casting.  He did this based on his personal experience with casting.

The comment was most certainly not directed at you. In the previous thread and in this thread you clearly said that you were in favor of pressure casting but that there were exceptions you had to read and casting techniques may have to be adjusted accordingly.  You made that very clear a number of times and I think you made a good case for pressure casting.  I was trying to flesh out whether there is a consensus toward pressure casting.  And maybe unfairly I was looking for facts and data to support one method over the other.

As an aside: yes I think people "cop out" quite often.  I think that whenever I hear people suggest that standardized practices are impossible because of the art or wizardly involved in making match grade bullets.  Or the other extreme in that there is only one way to skin a cat.  I have been taught and have deep belief in that the only one rule that is constant is bullet fit to bore.  I was taught that here and proved it to myself on the range.

Everyone has their opinion and I don't want to offend anyone but pressure casting is option two for me.  Bottom pour or ladle pour is what I start with.  But pressure casting is a tool that I wouldn't hesitate to use if things don't click.  Recently a 311299 mold took to not filling out the base.  I could probably have solved it in a number of manners but bottom pour pressure cast corrected the problem.

Maybe I'm guilty of blindly following how I was trained.   And that if I had been taught that pressure casting was always the first option I may have found success just as you laid out.  Its scary to think how good I could be if I took by blinders off. 








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Aaron posted this 17 December 2022


No worries. I was not offended in the least as I know your prose and personality from other posts. I read cop-out as "generalization" but wanted other readers to be clear that I firmly believe each mold has personality. They (the molds) can also show their arse on some days.

Every casting session is somewhat of a learning experience and there are times when the impossible, or what we thought impossible, happens. Once I was casting and after a lengthy session, the mold was quite hot. Frosted bullets were popping out perfectly formed. I discovered that I could cut the sprue by tapping the mold body and allowing the sprue plate to swing open with gravity. Nobody would believe that If I ever stated it so I never did.

We all long for that rare session when everything, and I mean everything, falls into place. Perfect bullets, time flying by, pile of bullets growing exponentially, and even the pot refill goes without a hitch.

Again, no worries on the commentary. I understood the prose and choice of words. And....if you ever catch me writing some bone-headed thing, feel free to call me a bone-head. It's all good.

\\ Aaron \\



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Wm Cook posted this 17 December 2022

I appreciate that.  Sometimes I accidentally step on peoples toes.  I do say things backward Ash or so I've been old.  You and I are good. 

This is related to pressure casting so I'll throw it in. 

Last winter I had a crazy couple of weeks turning things inside out trying to get another .001 on a bore rider nose.  During said stretch I jockeyed all the variables I had available; Linotype, #2 Lyman, Bottom Pour Cast, Bottom Pour Pressure Cast, Ladle Pour Cast, Ladle Pour Pressure Cast.  At the end of that stretch I made near nada difference in anything other than a little lighter bullets with the Linotype and maybe a couple tenths of a thousands greater nose dimension.  I'm sorry now that I didn't keep notes on that but I was going through a stressful casting period at the time.

However there was a happy ending to the story as someone here taught me how to beagle.  Thanks, Bill.

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Boschloper posted this 17 December 2022

Some thoughts / questions directed to Aaron:  You have observed personalities with the  64 molds you have on the shelf.  I have 20 ish on my shelf and have also noted personalities. Do you keep any notes or records of the personalities?  I have in a couple instances, and have thought I should be doing it on a regular basis. I have also had those casting sessions where nothing works.  I have turned everything off and walked away to come back the next day and had the same mold and the same pot of alloy work perfectly. I just shrug it off as part of this crazy hobby.

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RicinYakima posted this 17 December 2022

Everything Boschoper said. 

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Shopdog posted this 17 December 2022

Not too many regrets casting over the last 50+ years.....

One is,and that's keeping notes on moulds. Not only any quirks,but could also have jotted down any purchase notes(where,$$),history of the design... that sort of stuff.

I've done it with load notes,and the firearms themselves. Am having a degree of difficulty with a particular 6.5(260Rem) mould now. It'll get figured out but,would be nice to go over mould notes,just sayin.

Good luck with your project.

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Aaron posted this 17 December 2022


I do keep a running log on my casting sessions and the alloy lot numbers used. Most of the molds can get fussy at times and I do not track them. The molds that always give me fits I have logged. I know for instance that when running softer alloy in the RCBS KTSWC 38-150-KT, the bullets in the cavity next to the sprue plate pivot pin stick in the mold as the mold heats up. Tried everything to cure that issue but it's probably some microscopic metal detail causing fits.

I have other molds that like to run hot to deliver their best bullets and others like a cooler run. I have them logged so when I grab a mold, I can check to see if I have specific notes about it in my casting log. I have 12 molds listed that must be handled with more attention when used. The others run just fine with periodic burps not worth noting.

For some reason, my Lyman HP molds give me no trouble at all. I read with amazement the horror stories regarding them on some forums I used to read. I never had any problems with any of them. One does have to get them up to a good temperature and maintain a cadence however.

Other than sticky cavities, finning develops on two of my molds if the temperature gets too hot due to a high cadence. I simply slow down or grab another mold and run two molds concurrently.

My nemesis mold is a Lyman 358429 mold where the sprue plate screw keeps loosening despite all attempts to keep it secured. One day the molten metal gods will assist me with that. Until then I just keep an allen wrench handy. You have to tighten the screw quickly too since the little allen wrench make a wonderful heat sink.

So in answer to the question, I do have notes on the trouble molds and can expect issues with them as I use those molds.

I do the same with handloads and the tools for specific handloads. For example, the 38WCF. If I fire a cartridge in the rifle, then reload it, that cartridge will NOT chamber in the revolver due to the shoulder too far forward. I had to turn the size die down to set the shoulder back farther allowing the cartridges to chamber across manufacturers firearms. If you load for the 38WCF, you know exactly what I mean.

So I find it very beneficial to keep a journal or running log of my handloading/casting/range/firearm activities so I know what I have done with a particular firearm, how particular firearms like to be fed, and how alloy/molds will react on a good day or a bad day. That running log also assists old men, like me, recall what specific things I have done in the past to hardware. Makes good reading too when I discover that after grumbling for years about this issue, I can read about someone who corrected it and go back to discover I had/have the same problem which can now be be corrected on a tool or firearm.

Most of us on this forum, I presume, manage multiple firearms, calibers, molds, and are swimming in data regarding them. I don't know anyone trying to manage that much data that can do it from memory. If you only load for a single caliber or two, that's easy to do. With a dozen or more, things get complicated and a log or journal makes finding out particular details easy and repetitive.

 Here is an excerpt from my running log:

02/19/22    After modifying the Lee 38-40 Size die by removing about .030” from the face and “dropping” it some, the   rifle fireformed shells now chamber in the Uberti revolver after sizing with the modified die. The shoulder is now set back far enough for them to chamber in it.

Reloads made after January 2022 with fired brass from the rifle will now chamber in the revolver as well as the rifle. Reloads made with fired brass from the rifle prior to this date will not chamber in the revolver. Since it is too hard to distinguish between reloads made with fired brass from the rifle or revolver, treat them the same. Loads made with new brass will chamber in both the rifle and the revolver due to their extremely set back shoulder.

03/19/22    Loaded some 38-55 loads for the T/C barrel. Used the Hunter’s Supply bullets resized to .376". They chambered and shot fine. Used 24.0gr of RL7 and saw unburned propellant. Went to 22.0gr of RL7 and still had unburned powder in the tube. Had slight muzzle leading probably due to the candle wax lube of the factory cast bullets. Need to try some of the IMR propellants like 4198 or the like called for in the loading manuals to see if the high residue goes away.

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Premod70 posted this 26 December 2022

Would atmospheric pressures be a concern in the pressure discussion? I’ve read threads on another forum claiming they only cast on high barometric readings.

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lotech posted this 26 December 2022


I don't know what weight bullet you're using in the .38-55, but if you're getting unburned powder with RL7, increase the powder charge if it's safe according to reliable data. Decreasing the charge will only worsen the unburned powder situation. Or. consider trying H4895 (my favorite), one of the 4198s, 5744, or one of the 4227s. 

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Aaron posted this 26 December 2022


I find it amazing that you posted this when you did, Christmas Day at 7:15 ish EST. Today I received from Santa a copy of QuickLoad Software. Guess what it suggests I do to get more consumed propellant with RL7 in the 38-55? Yup. Up the charge. Bear in mind I am running a 14" tube with this barrel. Short by rifle standards and counterintuitive to "upping" the charge.

I can't wait to plug in the numbers on this cartridge to see what propellants will burn more efficiently. Thanks for the tip! Amazing timing.

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