Temperature variations and boolit weight?

[Jerry Lester]

If you start casting at say 700 degrees, and then change to say 800 or 900 degrees, would that change the weights of your bullets? I haven't tried it yet, but I'm figuring that at the very least, the mould would expand a little more allowing more alloy to enter the mould. I wonder also if the hotter lead being even more fluid in state, might possibly cast a denser bullet causing weight to be increased, and possibly even a harder finished bullet?

Of corse, this is just my mind doing what it does. I can't get into anything without analyzing it to death![smilie=1: :-D

[ron brooks]

From what I understand yes, they boolits cast at the higher temp will be a little smaller and a little lighter.

Please, if this is wrong someone correct me. :)

Ron

[Vly]

Jerry - I don't think you and I have the equipment to detect the difference between a bullet cast at 700 vs 900 F. In theory there will be a difference, but it makes no practical difference. There are too many other factors which have a bigger influence.
I strive for consistency is all my casting and loading. Thats how to get the most performance for your efforts.

[Dale53]

You can weigh the difference in casting single cavity moulds (precision casting for a cast bullet bench rifle) if the MOULD temperature changes between casts.

I strive to keep a rhythm going to have as near the same temperature mould for all casts as I can.

Lee Shaver, a BPCR shooter of my acquaintance, has his moulds drilled so he can insert (and leave) a thermocouple to keep a running record of his mould temperature while casting. He also records mould temperature so he can preheat to a predetermined temperature before starting casting. He claims (and I believe him) that as a result, he preheats his mould to a specific temperature for each mould and perfect bullets come out from the first cast on. It helps a great deal to keep bullet weights constant.

Dale53

[9.3X62AL]

I speculate that boolits cast at 850* contract a slight bit more in a given mold cavity than a boolit cast at 675*, based on the boolits being about .0005"-.001" larger when cast at cooler temps in my 45 caliber rifle molds using 92/6/2 alloy. This little tweak made a couple of these molds useful in the wide-grooved Ruger #1.

[John Boy]

If you start casting at say 700 degrees, and then change to say 800 or 900 degrees, would that change the weights of your bullets?
Jerry, the answer is Yes and them bullets are going to look like Frosty, the Snowman.
Variable melt temperatures effects the weight of any alloy mix you use.

Example: I cast many bullets for BPCR long range shooting. The magic number is to keep the bullet weights within a 0.5gr variance with the majority dropping within a 1 grain bell curve. Even 50 degrees will vary the weight of the dropped bullet. To achieve this bell curve, I keep the melt temperature so it does not vary more than 10 degrees

Further, the diameter of a dropped bullet will have a smaller base diameter & weigh more with a harder alloy - say WW's then a softer alloy (1:30) which will have less weight but a larger base diameter

Best advice is: cast at the temperature when you cut the sprue and the base of the bullet in the mold looks like a shiny nickel, is completely flat and has no lines on the base edges. Then you will drop perfect bullets with sharp edges on the bases and the whole bullet will look like a new shiny nickel

If you cut the sprue and the top of your mold has slush on it ... your casting too hot and the bullet will be frosted

[Sven Dufva]

I think the biggest problem is to hold constant temp on the mould. When you cast with 2 moulds temp will slowly increase and after aprox 1 hour will be to high. I usely stop casting in about 5 - 10 min. After first stop casting time to next stop will be 20 -25 min.
Another problem is feeding the pot and not taking down temp too mutch.

[Bret4207]

I certianly don't hold myself up as an expert, but if there is one word that applies to accurate cast boolit casting and shooting it's consistancy. I for one tend to prefer frosty boolits as they are almost always filled out better and tend to weigh out more consistantly for me. Any cosmetic problems are stictly in the eye of the beholder as they shoot as well or better than my pretty boolits. They tend to measure out more consistanly too if I do my part by maintaining a death grip on the mould handles too.

As far as their diameter goes I would think it would depend partly on the material the mould is made and partly on the temperature spread you're talking about. The bigger the temp spread and more sensitive the mould material is to changes the bigger the difference will be. Common sense. As to wether or not it will be a detectable difference on the range- that again depends on the indivual gun, load and boolit. My Turk Mauser 8mm couldn't care less what I send down the bore. It's shoots somewhere between Improved Cylinder and Modified at 40 yards! Some one with a real tack driver would be more apt to see the difference, especially in the throat area.

Experiment, try it yourself, maeasue and record the differnces. Then report back to us with your findings. Thats what we're all about here. What you find may be totally different from what I've said and that will add to the knowledge base.

Oh yeah, and try to HAVE FUN while you play with this stuff. Thats the main aim.

[44man]

I was told by the gentleman from Rapine that if I want a larger boolit, cast very hot because the mold expands larger.
BUT, I don't know what a harder alloy would do because all I was interested in was 20 to1 boolits for my BPCR.
I read a lot about smaller when hotter but have never experimented with my hard alloy. It looks like I will have to do it to see if there is any difference.
I do know my .475 boolits are much larger then my mold throws them after letting them age. I cast those very hot. My mold drops them at .476 but after a month or so they measure .478 to .4785. I never noticed this much growing when I cast cooler. With a colder mold they weigh 411 gr's but from a very hot mold they weigh 420 gr's. I use WW metal with tin and antimony added.
I would say the question is up in the air until extensive testing and measuring when cast and again after aging with each alloy.
I will not say yes or no but how do I explain the size and weight difference I get between hot and cold?

[9.3X62AL]

I agree, 44 Man. There are WAY too many variables at play to try making a "hard and fast" statement about how the many alloys and mold materials act when you alter one variable--temperature. Bret's text about consistency makes a great deal of sense, too--which may be another way of saying "controlling/managing variables".

As always--lots more like art than science. When the rifle or handgun shoots well, I'm ecstatic. I'm not real hard to please in that regard, and given my rather unscientific approach to this hobby field--that's probably just as well. :-)

[SharpsShooter]

Heat = fluidity of alloy= better fill out= more alloy per boolit= greater weight

Heat = mould block expansion = greater diameter = greater weight


That said, it is also important to maintain temps in order to maintain or reduce weight variables within a casting session. Careful note taking and repeatable alloy blends will allow you to achieve identical results on a frequent basis.

SS

[carpetman]

TprBrett--"If one word defines accuracy it's consistancy". I looked that word up and cant find it--what does it mean?

[Bret4207]

Uncle Ray- I take I didn't spell that right? You should know by now I can't spell.

[carpetman]

Tpr Brett--Just a pulling your change. It's very consistent that folks put an A that doesn't belong "consistant" no A should be an E.

[OLPDon]

The only thing lackin on Cast Boolits is spell check. If we did have spell check would it be Southern versen or Northern Version? Ifen I'm not mistaken it wouldn't be the Yankee spell check system.
Don

[Bass Ackward]

Tpr Brett--Just a pulling your change. It's very consistent that folks put an A that doesn't belong "consistant" no A should be an E.


Ray,

What's the matter with you. You prejudice or something. Consistancy is the Canadian spelling. Bret was just being .... international.

[Jerry Lester]

Thanks for all the good input!

Looks like I'll be experimenting quite a bit with this stuff.

[Bret4207]

Thanks for brining up the shamefull fact my druken ancestors got kicked outta Nova Scotia and Quebec Bass!!! OK, to be fair, they staggered out of Quebec and weaved out of NS.

Spell check would be nice. I fret over words like "basically, basicly, basicley" etc,etc. I hate to appear as stoopit as I really are.

[jhalcott]

Tip: The size and weight of bullets of a given alloy will vary according to casting temperature. Higher temperatures will result in greater shrinkage as the bullet cools and produce a slightly smaller and lighter bullet than one cast of the same alloy at a lower temperature.
copied from cast bullet references!

[NVcurmudgeon]

Without ever testing for weight variation at different temperatures, I try to keep temperature uniform just because it stands to reason. I try to cast with a constant rhythm, adding metal, fluxing and skimming at very regular intervals. After each adding, fluxing, and skimming, temperature is checked with an RCBS thermometer and the heat source tweaked as necessary. Most casting is done at 700-750 F. (I keep notes on each mould's preferred casting temperature, based on productivity and convenient casting.) Pistol boolits NEVER get weighed around here because I can't shoot a pistol that well, anyway. Rifle boolits being loaded for plinking and practice, don't get weighed either. Only boolits intended for load development or competition are weighed. Nearly all my weight sorted boolits are within 1%, so it could be said that my procedure works. OTOH, a very few boolits vary as much as 3%, so it can be said that my procedure isn't perfect! Either way, it's easy to condemn the off-weight boolits to the plinking box and move on. As far as doing a study of casting temperature vs. weight variation goes, I'm juggling enough variables now!

[John Boy]

Jerry, you may want to read and put into practice Part 1 and 2 of 'The 8 Phase Casting Cycle' ...
http://www.longrangebpcr.com/Part1.htm

After finding the correct casting temperature for each mold - caliber specific (because each mold 'like's' a specific temperature) and then applying the 8 Phase Cycle ... your gonna drop beautiful bullets

[44man]

The very first thing I read was the cooler mold will give a lighter boolit and a hotter mold a heavier one. That is what I have been saying but others say the reverse! Looks like we have to discount boolit shrinkage and look more at mold expansion.