Using 2 cavities in a 4 cavity mold or 1 in a 2 cavity

I have a mold that has a GC and PB cavity. Was thinking of ordering a 4 cavity or 2 cavity GC mold and having the GC removed from half of the cavities by hollowpointmold. The idea is for much of the time I don't need a gas check but for some occasions it is desired. So I have these questions.

How well does a 4 cavity (or 2 cavity) mold cast if one is only pouring in half the cavities?
Does casting with only half the cavities work better with 2 or 4 cavities? Or does it make no difference?
Might a 4 cavity that has a single cavity for when I want a gas check be a good option. Is single cavity out of 4 being poured a better approach than say 2 of 4.

Can you provide some feedback on the work done by Eric at hollow point mold? That is where I was planning to send the mold to have the GC removed from some cavities.

I figure I'm probably going to make a several hundred of both styles initially by casting in all cavities to build up a stock of them and then only want to cast in the cavities that replace the base style I have used. Just don't know how well casting with half a mold will work. Or if there is a technique that makes it practical.

I am inclined to get a 2 cavity and convert one cavity. If that will cast ok or better than a 4 cavity then I figure a couple of hundred from a single cavity once in awhile isn't too much work and don't figure to burn through more than that over a couple of shooting sessions with a revolver. If 4 cavity will work better for using part of the mold then what the heck I'll get them done faster and have to spend more on the whole thing. But better and more money do tend to find each other all to often.

Whatever a 2 cavity mold does, the 4 cavity will do faster.
You might consider using all the holes, and just separate the flat base and gas check ones.
Or use a gas check design for everything, and just don't put the checks on some.

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Originally Posted by Winger Ed.

Whatever a 2 cavity mold does, the 4 cavity will do faster.
You might consider using all the holes, and just separate the flat base and gas check ones.
Or use a gas check design for everything, and just don't put the checks on some.

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Have heard that GC base is somewhat iffy for accuracy without a gas check, never tried it myself but that is what many folks seem to think.

Problem is I won't need GC nearly as often as I will plain base so if I cast and separate I will just build up a large supply of GC bullets I'm not going to use. If I shoot 200 PB then I really need to cast 200 PB to replace them, rather than cast 200 of the PB and add another 200 to the GC version stash which I didn't use any of. Or vice versa. Using 100 of the GC shouldn't require making a hundred of the PB which were not used in order to replace the 100 GC bullets that were used.

Speed of a more cavities is good. Provided it isn't unusable or a poor choice to cast using only half the cavities.

I have an old Lyman #311332 that has a big rust divot in one cavity, I still fill both cavities every time I cast with it. I tried filling only the good cavity, but found I was getting more rejects because the mold wouldn't stay hot enough. So I fill both cavities and sort by running a bullet in my fingers while I'm watching TV.

i have done a little of casing 1 in a 2 hole and in a 4 hole casting 2.some molds seem to work better than others. the 2 hole aluminum needed a lot of heat and it worked ok.a 4 hole aluminum didn't work as well seemed to be to much mass to keep in the right heat range.that is all of that I have done.Migh be if you have a large heavy block it would do better.

Does anyone have good luck with the aluminum gas checks produced for plain based bullets? That would give you the option of adding the gas check when needed, without the issue of omitting the check for a bullet cut for a check.

I use the Lee 6 cavity handles on several of my double cavity moulds, some moulds require the slight thinning of the metal in the mould area but they are great value and I like the extra length. I think you will find that you don't have to use checks on a gas check mould as they shoot as good without them if not needed. I agree with what others have said if you modify a cavity still pour both as it is a pain trying to pour one. Regards Stephen

I use Sage's aluminum gas checks for PB 9mm bullets in my carbine and also the one's designed for undersized gas check shanks in 44 caliber. They work as intended but aren't that much cheaper than the copper ones. Would much prefer a mould that will drop bullets with correct sized shanks and use the copper ones, but sometimes that isn't possible.

I had a large stockpile of PB 9mm bullets, that did really well in my pistols, but not so much in the carbine at higher velocities it produces. In order to use them I installed the aluminum gas checks.............it was worth it. However, I won't go that route anymore. I just ordered a clone of that mould, added gas check shanks and increased the cavity amount.

Almost all of my pistols have a carbine chambered in the caliber. When I purchase new moulds I always go with half the cavities gas checked. It is possible to cast without pouring all the cavities but I have never done it. With complementary firearms, I don't find it necessary. I will use the PB in the pistols and GC, in the carbines. During load development for the carbines, I start with PB, at the lower end of the spectrum and move to GC at the higher end. YMMV


Winelover

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Originally Posted by RogerDat

Can you provide some feedback on the work done by Eric at hollow point mold? That is where I was planning to send the mold to have the GC removed from some cavities.

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My friend and fellow member "Biggin" just had Eric remove the bevel on a H&G 68BB mold. The workmanship looked great but I don't know if he has cast with the mold yet. Maybe he will see this and add a comment.

Tom at Accurate Molds will make a mold with different cavities for a modest extra charge.

The few times I have tried casting just a few cavities in a mold have been mostly unsuccessful. As the others have posted, maintaining the correct temp is the problem.

I am using a mould that Eric had modified. The RCBS 44-300 SWC GC. Converted to HP and one gas check shank removed. Work of art and casts like a dream. However, his work does not come cheap. IMO, worth it if you have a favorite mould that isn't available with the options you want. Cheaper to order a new mould from a custom maker.

Attachment 236044

These are an example of the bullets, I cast, with the modified mould. The mould is on loan from cbrick.


Winelover

Seems like you will use PB a lot more than GCs. Why not go with three and one. Also cast all four and if you are accumulating too many of one type, just throw some back in the pot and remelt them.

I shoot .45-70 GC type boolits PCed with out the gas checks, with simple iron sights and don’t think there is a difference over PB. The PC seems to fill in GC space a bit. With my 6.5mm with diopter sights, I definitely need GCs, PCed or not.

I have a 4 cavity mould from Accurate that has 3 flat bases and 1 gascheck cavity.
I just use all 4 at once and separate later.
Never tried only using 3 cavities. I just want more boolits faster.

Quote:

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Originally Posted by RogerDat

I have a mold that has a GC and PB cavity. Was thinking of ordering a 4 cavity or 2 cavity GC mold and having the GC removed from half of the cavities by hollowpointmold. The idea is for much of the time I don't need a gas check but for some occasions it is desired. So I have these questions.

How well does a 4 cavity (or 2 cavity) mold cast if one is only pouring in half the cavities?
Does casting with only half the cavities work better with 2 or 4 cavities? Or does it make no difference?
Might a 4 cavity that has a single cavity for when I want a gas check be a good option. Is single cavity out of 4 being poured a better approach than say 2 of 4.

>>>SNIP

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My 2¢ and a bit of experience...
It depends on the mold and size of the cavities.

I found with one mold, a NOE 460-405 RF that is a two cavity mold, one PB and one GC, that I have to actually cast slower when pouring both cavities, because that large boolit design makes the mold overheat easily. So I always cast just one cavity with that two cavity mold, I find I can cast faster, not just because I'm only pouring half of the cavities, but I'm pouring less "heat", allowing the mold to maintain a correct temperature so there is less wait-time between pours.

NOW, a mold with small size cavities, in comparison to that example, like a RanchDog mold I have (6 cavity Lee blocks) 358 190gr (3 with GC and 3 PB), That mold I find I need to pour all 6 cavities to maintain a correct mold temperature, so that's what I do, then just remelt the style I don't need, or just put them on the shelf.

Good Luck,
Jon

Well thanks one and all.

The cost of having the GC shank removed or driving bands increased in size by Eric at hollow point molds is $35 set up + $5 per cavity. Cost of a second mold would be over $100, buying a mold for him to hollow point as much as I like his design would also be a bit more expense than I really want. Would love to try his system but... also wish to not give wife that much good reason to be mad at me.

I'm thinking the idea of go with PB and buy a Pat Marlin's PB35 check maker has some merit. This would allow me to add checks to any PB .38 caliber bullet I cast probably using aluminum beverage cans as the source metal. The check maker is $100 so having a "regular" check maker vs a plain base one for that cost is the issue.

I have an NOE mold that does PB and GC for 303 British and it works out ok, as winelover says the PB makes a good plinking round at the low end and the GC is good when I want to push it a bit. I also like knowing if I have lead but no GC's I can still make good bullets.

I suppose I can always try the GC bullets without gas checks. In a snub nose at 10 yards I think there is enough feed back to suspect it can perform adequately. If wife or myself do our part as they say.

The mold will be brass so that "might" help with the heat retention but I think the idea that will probably work best is the "do over if I don't want re-melt" Cast in all cavities, sort, and if I find I don't want 1/2 of the output toss it back in the pot.

The GC shank can be removed but not added and the cost would be modest compared to a second mold, having the time to budget for that removal as a future enhancement works well for me. Same for purchasing a check maker, I like knowing I can produce what I need without concern for market conditions but I can also wait a bit, a bag of 1000 checks for $25 will last a long time especially if it turns out they are not always required.

The 4 cavity vs 2 cavity is going to come down to a coin toss. I like productivity of more cavities. I could be content with a 2 cavity. Even a 2 cavity modified to be 1 of each would be ok since I consider hollow point something of a special limited production item. Weight of brass is also a consideration. Still a 4 cavity GC now and a potential 2 & 2 later is most tempting.... :confused:

Just for the record I went with a 2 cavity GC mold. IF my math is correct it would be slightly less expensive to purchase a second 2 cavity PB mold instead of modifying a 4 cavity. While avoiding the extra weight of the 4 cavity.

Reason not to buy the garden tool that is a hoe on one side and a cultivator on the other. It does either job less well than the single purpose hoe or cultivator. Plus you are working with the extra weight of the tool you aren't using. In this case having to hold up larger mold and fill cavities I don't really want to use is a lot of extra working weight. Cost of removing GC shank and shipping is more than 1/2 of the cost of 2nd mold with 2 cavities.

Only reason not to just up and order them both is the cost is all at once. I have a feeling that "new mold" and "$182" might be something I don't say around the house unless I can say "from the lead and brass I sold" So I ordered the GC 2 cavity which I have budgeted for and will see what I have in the stash to sell. If I can fund a second mold that is a PB 2 cavity that would be great, if not then I can decide later about removing a gas check shank for a 1 & 1 mold or just have all my HP for 38/357 be gas checked. Extra work and cost to GC bullets but not a really big deal.

My own guess is lead soft enough for good expansion will be more likely to need a GC than not.

Hey Roger,
In addition to the notes I made outside the forum one thing to also consider is PCing.

I talked with Charles who used to make the FreeChex system and his opinion was that for most purposes the PC would do as well as the gas check.

I have also asked my dad (who professionally does ballistic testing) to test this with 44s that I have cast for him (429-244s GC). Thus far in his testing he has seen identical results from the PCed, the PCed with gas check, and the traditional lubed with gas check when shooting standard pistol distances.

Just another consideration that could save you from having to have the same mold multiple times.

I have some H&G 4 cav molds that have 2 different designs in them.
I f I want only one of the designs I bring the mold up to temp and on the hotplate and cast with the 2 I want with my bottom draw pot.
It works just fine casting with 2 of the 4 cavities.
If I get some slop over in the cavities I don`t want I just toss it back in the pot with the sprues...dale

On the mold weight question I tested a few molds I had in 38 caliber for comparison ranked heaviest to lightest):

H&G 6cav iron (#12 150gr) empty - 4lb 5z
MP 4cav brass (HG50 HB 150gr) - 2lb 11z
H&G 4cav iron (#50 150gr) - 2lb 1oz
MP 2cav brass (358-429 HP 170gr) - 2lb 0z
NOE 4cav alum (402-150-hp 160gr) - 1lb 15z
Lee 2cav alum (401-175 175gr) - 0lb 13z

All weights include handles and pins with cavities filled but no sprue unless otherwise noted.

Sorry for the aluminums being 40 caliber but their the only two aluminums I own and the 6cav hg 12 is a 38 caliber but is newer to me so haven’t filled yet.

Some good information here. For example IF filled the H&G 6 cavity iron mold would double as a dumbbell for doing 5# curls. :-)

I find a 4 cavity NOE aluminum comfortable so given StuBach has almost the same 2 cavity MP brass mold I'm getting at close to same weight as that size NOE I'm pretty sure I'll find the 2 cavity brass I ordered comfortable in terms of weight.

Checking 3 boxes. Wanted to have a HP for that caliber, wanted to try the HP pin arrangement used in MP molds, want to get a brass mold. Now I just have to hope that I don't develop an extreme fondness for brass molds. Have already seen some around with that expensive addiction.

Thanks again for all the insight and experiences shared.

I like 4 cavity molds because I'm still able to handle a 4 cavity iron mold ok. But the day may come when I can't. I am actively searching for 2 more H&G molds and I have passed up a few deals on 6 and 8 cavity molds because of the weight. The effort required with the 4 cavity molds is still worth to me for the production that I get.

You have a good idea, buying 2 molds, each doing what you want vs the cost of modifying a single mold. And it probably would be easier to sell a factory mold vs a modified mold if you ever want to.