4-Cavity results Better Than 1- Or 2- Cavities??

[BruceB]

During the present run-up to the Nevada Cast Bullet Shoot, I've been paying a lot of attention to certain moulds I own, and their bullets, of course..

Prominent in the group are several rifle-bullet moulds, namely (all 4-cavity types) our famous 311291, the old spire-point 311413 (and this mould itself is OLD, being Ideal-marked and rather badly pitted in places) and a 311467, the nominally 180-grain Loverin design.

Casting roughly a thousand or so of each design in straight wheelweights, and water-dropping them from the mould, I found something interesting which had not drawn my attention before this prolonged exposure to the group of 4-cavity moulds, AS A GROUP.

My inspection routine is entirely visual, but it became far more stringent after I bought one of those pivot-mounted lights with a 4" magnifying lens. I have never seen cast boolits so clearly, with all their naked imperfections laid bare! This lamp may be the best $10 I ever spent in casting gear. Previously, I'd quote my reject rate at a couple of per cent, if that. I now reject a good many more than that, but it's just because I can REALLY see the flaws, now.

So, back to these four-cavity moulds. Under strong light and magnification for 100% inspection, and with each design represented by about 1,000 bullets, I rejected only THREE 413s, SIX 291s, and ELEVEN 467s (the 467s really surprised me, as it's a very "busy" design with many grooves and bands).

Having all three moulds giving these results in close sequence, I have to think there's something about them which gives more-consistent casting results than smaller blocks. Even with bullets coming from four different cavities, the weight range of each design is barely one grain extreme spread, in ALL THREE moulds. Dimensions are also very, very close among bullets from the four holes, in all three moulds.

My rejection rate from smaller-block moulds is a good bit higher than the numbers above, even in my much-favored RCBS double-cavity examples. I suspect that my standard routine of hot/fast casting (870 degrees) gives me a hefty heat-sink in those big blocks, which also would tend to allow excellent fill-out before the alloy freezes.

I'm commencing to think that even with whatever variables are introduced by using four separate cavities, the end results are better than I get from smaller moulds!

[No_1]

Interesting reading. To further your thoughts, have you considered casting from less than all cavities in a particular mould to see if running only 2 or 3 out 4 would give the same or different results? This would/could verify thermal consistancy.

Robert

[Dale53]

BruceB;
I only use a single cavity mould for my Schuetzen. Precision accuracy (1/2 minute is necessary to be competitive). However, when I was shooting BPCR Silhouette Rifle I used four cavity moulds with excellent results (six inch ten shot group at 500 yards). I have a couple of good rifles for BPCR and I could not ask more of the bullets I got from the four cavity moulds.

You may be on to something about the "heat sink" properties of a four cavity mould. A caster tends to do things more in sequence when using a multi cavity mould, in my experience, and you just may be more consistent in maintaining mould temperature. Letting a mould's temp flucuate tends to produce bullets larger and smaller depending on mould temp and the bullets weigh heavier and less depending on their as cast size (you can weigh the difference much easier than measuring the difference).

Dale53

[Bucks Owin]

Guess I'm a little "wimpy" but my arm gets tired from handle a DOUBLE cavity .44 cal steel mould for 500 boolits....
Guess I need a mould guide! ;-)

It seems to me that one cavity usually throws slightly better boolits than the other. If I'm after max accuracy rather than just practice boolits I'll only use the "best hole" for casting. (These are Lyman, Lee and RCBS moulds BTW) Maybe the really expensive moulds are that way for a reason? Like consistency?

FWIW,

Dennis

Although the best mould I own at present is a used RCBS which dumps beauties....(.44 250K)

[David R]

BruceB,

Good reading. I use a infared temp gun thing when I cast. My Lyman 4 cavity 452460 keeps the most stable and EVEN temp of all my molds by far (my only steel 4 banger). This shows me that it should produce the most consistant boolits.

My temp gun is a Ray Tec. cost almost a hunert bucks and was well worth it. I use it in other hobbies too. It will not work on lead because it only goes to 500 f and the infared reflects off shiny surfaces. On a new group buy mold, it reads way cooler than it is until the bottom of the mold gets discolored from placing it on the wet rag quite a few times. The instructions say to spray the shiny items with flat black paint to get the best reading. I won't paint my molds.

David

[Blacktail 8541]

I've spent a lot of time trying to decide if multiple cavities were worth the expence. IE cavities produceing dimientialy repeatable bullets, Bruce your insite brings me a little closer to purschasing one.

[ANeat]

BruceB,

Good reading. I use a infared temp gun thing when I cast. My Lyman 4 cavity 452460 keeps the most stable and EVEN temp of all my molds by far (my only steel 4 banger). This shows me that it should produce the most consistant boolits.




David; I was wondering what the mold temp is once you start getting good bullets. That is something I have been meaning to check.

Adam

[David R]

Aneat,

250 to 300 on the bottom of the mold. Its mold specafic. In that range, boolits will be good, a little galvanized looking. This is not cavity temp.

David

[montana_charlie]

The instructions say to spray the shiny items with flat black paint to get the best reading. I won't paint my molds.
I use a spray-on graphite on all surfaces of all my moulds except the faces and cavities. When lead sticks to the surface, it just wipes off...and it prevents galling between the mould and sprue plate.

It also gives the entire mould a flat, dark grey color.
CM

[Bret4207]

I have a 10 cavity H+G 38 WC mould. Once that sucker is up to temp the booilts threaten to outpace my feeble attempts at pouring lead as they reproduce so fast. I will not say that I get "less than such %" rejection rate. I just don't cast that way. I will say that if I give it a good run, (till my arm wears out), there can be a pile of 5-600 acceptable boolits and a very small pile ,35-40?, rejects. The heat sink proprties seem to be the answer. Or at least an easily used anwer. Block quality sure helps too.

[DaveInFloweryBranchGA]

Montana Charlie,

What brand of spray on graphite do you use?

Thanks,

Dave