Single/Double cavity molds for accuracy?

[Charlie Horse]

Does anybody prefer the slower output in favor of better consistency? I've got a couple 2 cavity Lee molds for 38/357/9mm for pistols and one rifle. Long story short, I get much better groups with boolits from the 2 cavity molds than anything from a 6 cavity. Not trying to be Captain Obvious here, but I'm thinking of getting some 2 cavity versions of some 6 cavity molds just to get better groupings.

[ioon44]

I use Accurate 5 cav molds and the weight and diameter of the 5 cavities very close to the same, the quality of the mold is more important than the number of cavities. Uniform bullets are only the first step for getting better groups.

[Mal Paso]

The one 6 cavity Lee mold I have varies slightly in diameter from the first cavity to the last. I haven't had that happen with my 6 and 8 cavity MP molds. Not a Lee hater but there are better quality molds out there.

I preheat molds on a hotplate. I've never noticed a difference between 4, 6 and 8 cavity molds. Never had a 2 cavity.

[Winger Ed.]

Some folks would use only one cavity from even two hole molds to try and eliminate that one last variable for accuracy.

Just being curious, I've weighed ones from both cavities in a couple and the difference was so small-
I don't think I can shoot good enough for it to matter.

If you go down that path:
I'd think you'd be better off and it would be faster to cast up a bunch, then weigh them.
I'd get a electronic scale you can trust, then segregate them in lots of maybe .1 or .2 grain differences.

Even if you only use one cavity, you might get inclusions or voids like a shrink hole
that would give different weights.

The weight differences would show up more and more at longer and longer ranges.

[lightman]

I have measured and weighed bullets from RCBS 2 cavity molds and from Lyman, H&G and Saeco molds and have found them very consistent. I haven't checked anything from a Lee mold except once about 50 years ago. The bullets from a 2 cavity mold varied in weight and diameter. Not hating on Lee, just stating what I found.

[Harter66]

From Lee what I've found , it's not a hater thing I have 5-6 sixes and 10-11 singles and doubles , when they're on they are really close and when they aren't they may as well be the Sox . One Red , one white . The 6 cavs throw 3 very close , 1 light, and 2 heavy . It doesn't change from 00B to 358-200 or 452-255 .
I have 2,3,4,5 cavity NOEs the 3 cavity when I do my part throws 460-535s at .460 +-.003 and 534.7-535.6 without a visible pattern . The 5 cav 454-250 SWC version of the 454424 drops what the mould is called +- 2 gr of operator error .
The 2 cav M-P 462-420 drops 2 bullets and frankly I can't measure a difference unless I swap the PB for HB pins .
When the Lyman 4c will play nice , 258312 , which is something we are still negotiating, I get 4 bullets within 1.5 gr of a median weight . As I said though we're still just tolerating each other.
The H&G 8 cavity , again when I do my part , drops 8 bullets 195.6-196.5 .

I have better moulds in 2 cavities that vary as much as Lee's and some that may as well be one . The Cramers come to mind as a 2/1 while RCBS delivered me ,2nd hand , a 7mm-168 that I will eventually fix to not only match weights but have enough nose to touch brand new better quality lands and a 27-150 that I may have to nose size to make fit , but weights are dead on .

2,10,50 or 500 perfect matching bullets 100% minus operator error takes a single .
1% or less weight and shape variations isn't hard to get from the better names but once in a while you're going to get a dud . See my 7mm-168 .
4+ cavities can deliver the goods at 1% but it takes a good mould and an operator that has the focus to really manage the pours , timing , and repetition .

A single will give you 1% all day long as long as the mould , sprue plate , and melt are stable and the timing is fairly stable . Bad timing too hot , too cold , and a single you're trying to make time with is as bad or worse that a 6 cav Lee made and boxed on Boxing day or the 5th of July.

[gwpercle]

I like to cast the best , most perfect boolits I can . And for me using an open top pot , Lyman spouted dipper and pressure casting is the way I get my best boolits .
I use 1 , 2 , 3 and 4 cavity moulds with my dipper .
Handguns can get by with multi-cavity moulds ... Precision Rifle ...1 - cavity is best ...
but 2 - cavity , from a good maker , will do fine .

I tried casting with a bottom pour pot with everything but a Lee 6-cavity mould ...
I could cast a whole lot of slightly defective and a few almost perfect boolits with that method but I didn't want that ... I gave the bottom pour to a fellow member and went back to open top 20# Lee Magnum Melter Pot and Lyman dipper and pressure casting . If I'm going to take the time to cast ... I want perfect & consistent boolits 99% of the time .
The way the custom makers make moulds ... CNC machining... the cavities aren't that different . My favorite moulds for pressure casting are 3 or 4 cavity . I'm older now and NOE 4-cavity are my weight limit , NOE 3-cavity are my favorite simply for the weight and how they handle ... Yeah , getting old sucks ... hand strength becomes an issue .
Gary

[Geezer in NH]

To op pistols nope use as many cavities as possible that you can afford.

Rifles 2-cav are what I start with and Great mould up to 4 gang as all I can hold. I am 70 and arthritic.

[Green Frog]

For my Schuetzen rifles I always use single cavity moulds, then fire the unsized bullets, freshly lubed, in the order cast. For pistols and revolvers I like 2-3 or more cavities since I’m going to size them when they’re lubed anyway. The single shot rifles use them up more slowly anyway!
Froggie