Single vs Double Mold

[GregLaROCHE]

I’ve done most of my casting with double molds. Now I find myself using some single molds, because what I wanted was only available in single, or the mold came with the gun. I’m realizing that it takes a lot more time with a single mold than a double. I’ve been wondering if there is any advantage with single molds in the quality of the boolits, or maybe they are that much easier to make and therefore cost less?

[Bazoo]

In the book, the Art of Bullet Casting, there is an article by one Mike Venturino, in which he tests the accuracy of bullets produced by the individual cavities of a double cavity mould. I don't remember the caliber, but it was a revolver caliber such as 44 mag or 45 colt. He marked one of the chambers to use during the test, and clamped the gun in a rest. A lee rest if I recall correctly. He cast bullets from several 2 cavity moulds, keeping them separate. He prepared them identically and fired them on paper and recorded the results. The results were that one of the cavities produced a smaller group than the other, and the poi of one was slightly different than the other. It was quite the read. I let that book get away so I can I offer more detail.

Moulds made on a CNC machine probably are more consistent that the old cherry and mill cut moulds.

[leadhead]

I hate single hole molds....... And I don't think it makes one bit of difference using
double or multi cavity molds as far as the quality of the dropped bullets go.
I've used 6 cavity molds, and the bullets don't vary more than 1 gr difference between
them and you would never be able to tell by shooting them a difference in accuracy.
Denny

[Mk42gunner]

My two word answer is: It depends.

My longer answer is: If you can shoot good enough to tell the difference, decide if it matters to you. If you can't tell the difference, it doesn't matter.

For me, if it is for a rifle that I don't shoot a lot, (or hunting) I don't care if it is a 1,2,4 or 6 cavity mold. If it is for a handgun or high volume shooting (plinking), I want the most cavities I can get.

Robert

[22cf45]

For rifles, I will only use single cavity molds. I have some double cavity molds but I keep the bullets separated according to the cavity. I tested them and although both cavities shoot well, they do shoot to a different point of aim. For pistols, multi cavities are just fine since I've not trying to shoot 1/2" groups at 100 yards.
Phil

[GregLaROCHE]

For those of you who think a single will produce a more constant boolit, due you have any ideas or guess why? Maybe a single has more all around equal heating and cool of the mold?

[Green Frog]

For rifles, I will only use single cavity molds. I have some double cavity molds but I keep the bullets separated according to the cavity. I tested them and although both cavities shoot well, they do shoot to a different point of aim. For pistols, multi cavities are just fine since I've not trying to shoot 1/2" groups at 100 yards.
Phil

When I shoot for real precision rifle work (Schuetzen) I use single cavity moulds and shoot the bullets as cast and in order cast. I’m trying to eliminate as many variables as possible, especially when shooting cast bullets from a bench rest.

OTOH, I prefer DC (or more) for pistol and revolver bullets... my accuracy with those is nowhere near as good with the handgun, so whatever differences there are between mould cavities seem far less significant. Also, for most rifle shooting I’m shooting targets at distances anywhere from 2-4 or more times as great, so the effect of small differences gets multiplied.

These are my personal experiences and the conclusions I have drawn, and as with all things, YMMV.

Froggie

[country gent]

With cherry cut moulds there may be a slight variation between cavities do to machine play cutter sharpness operators skill and material. A lot of the machines lyman used for making moulds were made in house and were a cross between a heavy drill press and knee mill. These were very heavy solid machines and when new very good but threads and ways wear inducing backlash and play. With this separating by cavity and shooting in groups may be a benefit

With the newer cnc cut moulds ( lathe or mill bored) variations will be much smaller between cavities. The nature of these machines and the programming makes them very
constant, along with the ball lead screws and better ways designs. SO on these moulds separating then by cavity may not make as big a difference

[georgerkahn]

I "cut my casting teeth" on an H&G #50 2-cavity mould, and have been partial to two-cavity moulds, since. As I get older/weaker, too, the 6- and 8- and 10-cavity moulds have sadly gotten too heavy for continuous use for very long. E.g., fifty fills, sprue cuts, and dumps with a four cavity (brass or iron) mould are, bion, no longer as much fun as, say, 100 uses of a two-cavity mould to yield same production.
I DO have a few single cavity, and about half of which are rifle bullet moulds which were available (e.g., listed here or an auction site) and I wished to try; sometimes, for an off-beat calibre needed -- with the other half being pistol calibre hollow pointed moulds of the Lyman flavour.
In terms of the finished product -- I believe I get the same percentage of those I'm happy with, as well as a bit disappointed with -- from all moulds -- with number of cavities not being a factor.
geo

[MT Gianni]

I believe that cherry cut molds used to differ enough a sc mold gave much more consistent results. IMO, You have to be a very good shooter to get the benefits of indexing bullets and cartridges but the older shooters got much better groups by doing so. Many of us cannot duplicate our bests groups on request and I don't believe that range conditions are the only variable.
There used to be and old commercial I had issues with, something along the lines of "Do one thing, get to be good". I believe that it takes good practice techniques and equipment to be good and excellent techniques, equipment and genetics to be excellent. Those competing in that highest class in all area, need to take every advantage they can. For some it will never help, for the rest of us, we have to evaluate time spent to results gained.

[dverna]

With pistol bullets I doubt it matters much. My mentor and I would shoot 50 shot groups at 50 yards using a Ransom Rest. We both used H&G 10 cavity molds. Groups with the Remington HBWC (likely the best 148 gr bullet every made) were 1/2-1" smaller than our cast bullets (visual inspected only). We both used the 148 gr bullet at 50 yards for competition. At the distance most pistol bullets are shot, multicavity pistol molds are the only way to go. But a bolt action rifle is inherently more accurate than even the best Bullseye pistol. The standard changes

It makes sense that a single cavity will produce more consistent bullets but is it worth the effort? How does that effort compare to the effort load a prefect cartridge...to uniform neck walls and flash holes..etc etc..or how a lube works at 30* vs 85*. And then the alloy and powder???

In the search for accuracy, I gave up with cast rifle bullets. You can buy almost any commercial bullet and outshoot 95% of the groups displayed on this site. You will not need to do much case prep, or extensive load development (playing with alloy, sizing, lube, powder, casting cadence, primers). I have not done the work, but I doubt that the difference between cavities amounts to much of an effect even on rifle bullets. Be thankful if your cast load is a true 1.5 MOA. BTW, the smallest 10 shot group ever recorded with a Production rifle was shot in 2006 and measured 1.323" (just over .65 MOA). It holds the CBA Record. Take claims with a grain of salt....even a blind squirrel finds a nut once in a while. When the best cast bullet shooters cannot do better than .65 MOA, after 14 years of competition, it puts things into perspective.

A 3 MOA load is going to harvest a lot of game under 200 yards. We are more likely to miss due to poor range estimation or a bad shot than the accuracy of the load. Keep your ranges reasonable and you will be fine. Use a multiple cavity mold. If you want to weight sort them, it cannot hurt, and it more efficient than using a single cavity. I would keep the ones that weight within .3 gr of the heaviest weight. For giggles make up some loads with bullets that vary more and see if it matters. I tried that with a .308 and it was not worth the effort...I used a Lyman single cavity and straight Linotype YMMV.

If you want an accurate long range load, buy a name brand jacketed bullet.

[Guesser]

I really enjoy using my old Ideal SC molds as well I have a number of long discontinued Lee SC. They are a delight to use, easier to maintain temperature and rhythm, all castings are identical and they are light and quick.

[longbow]

I'd tend to agree with previous comments that with cherry cut moulds there could be enough difference in cavities to be noticeable especially for serious target shooting and/or long range shooting in rifles but not so much difference when moulds are CNC cut. Not saying that some cherry cut moulds do not have virtually identical cavities but I think there is far more likelihood of chatter or other errors in cherry cut moulds leading to differences in cavities than with CNC machined moulds.

Using a single cavity mould ensures that boolits are pretty much identical, if casting quality is good, so removing the possibility of slight differences in cavities.

I've got moulds from single cavity to 6 cavity but have always preferred casting with two cavity moulds. Different strokes.

I will say that there is so little difference between cavities in my NOE, Accurate and Mihec 2 to 4 cavity moulds that I doubt I could tell the difference but those are all CNC cut moulds. I have at least one cherry cut Lyman two cavity mould that is not so precise.

Longbow

[Jruby38]

Yes, like Duerva said. I doubt any shooter here is good enough to see any difference offhand at 100+ yards.

[barnabus]

if you weigh and separate bullets from mult-cavity moulds then shoot does it really matter? opinions?

[jonp]

I use both and other than casting twice the boolits at a time I've seen no difference but I don't benchrest or anything either. I'm also not in a hurry so it doesn't really matter how long I cast as it's a hobby for me.

[Rich/WIS]

Lee gets bashed a lot but a 6 cavity Lee isn't much heavier than a 2 cavity steel mold and has a better system for cutting sprues. If NOE (or some enterprising machine shop) ever comes up with a replacement 5 cavity sprue plate that would take a Lee sprue cutter handle I know where they will get an order for four.

[georgerkahn]

if you weigh and separate bullets from mult-cavity moulds then shoot does it really matter? opinions?

Many years ago (and perhaps some still do this?) it was not uncommon for casters to punch teeny prick holed in the noses of each cavity of multiple cavity moulds, so after casting they could segregate all the ones with, say, one prick hole from the ones with none; with two.... -- and the like. The theory behind this was due to the believed "impossibility" of all cavities having been machined identical to the others in same mould.
Partially because I never was a good-enough pistol shooter for it to be noticeably significant at the target to me by so doing, my thoughts included that -- if you were loading un-sized un-lubed bullets: yes, teeny differences may show. BUT, after weighing -- even from the same cavity -- and then sizing and lubing -- any differences -- if significant or not -- again, were not worth the time and effort. In retrospect, however -- I would be loose with the truth if I did not add the MUCH enjoyment came from "fun" things we did to try and improve our scores, after buying more S&W barrels than ever needed by a sane group of shooters; buying any and every gizmo Gil Hebard and others purveyed, and doing hundreds of very minor changes in our loading procedures trying to attain that extra point.... :)
geo