I use a synthetic 2 cycle motor oil on all my molds when casting, it flat out works.
I own 20+ brass molds and wish all my molds were brass. I'd put my brass molds up against the h&g's & cramers's, you just can't beat the consistency and quality of the bullets a brass mold produces.
Brass molds tend to be cut better/have cleaner lines with low runout. They also have a more consistent/even heat displacement with low heatsink areas.
The temperature of your alloy has a lot to do with a molds performance & bullet quality. I run my alloys for casting @ 725* and will bump it up to 750* if I run into issues with molds like the H&G #38 "Ness" bullet that have extremely long hp pins that are a nightmare to keep hot/bullets from sticking.
I like to run my molds hot and pre-heat them on a hot plate. I heat them hot enough so that on the very 1st pour the alloy puddles on the sprue plate and takes awhile (10/15 seconds) to harden/solidify. Those bullets get tossed and I'll repeat the pours taking 15/20 seconds between casts slowly cooling the mold down. When the sprue puddle gets to where it takes 4/5 seconds to solidify I start keeping the bullets. The bullets will either be frosted or on the edge of being frosted.
This is where the brass molds really shines, they hold that heat very consistently & that leads to the 3 main things you want in a cast bullet. Namely a consistent diameter, full fill out/sharp edges and no voids.
Consistent diameter ='s consistent weight
Consistent long solidify times ='s sharp bullet bases & drive bands
Consistent long solidify times on the sprue puddle ='s no voids in the bullet.
This is where most caster either go wrong or their molds fail. A lot of casters don't like frosted bullets or use a frosted bullet as a sign that the mold is getting too hot. That leaves +/- 50* of variance in their molds which leads to voids in the bullets and differences in the bullets diameter along with inconsistent bullet bases/drive bands.
I have nothing against lee molds , I simply won't use their 2 cavity molds. There's massive heat swings in the mold temps in the same casting session. Some use 2 different molds to cast at the same time to slow this down/try to keep an even heat in both molds. I only use lee 6-cavity molds and I run them hot, hot enough so the bullets are borderline frosted. I also use a damp rag to cool the sprues, doing this allows me to have better control of the molds temperature, cast bullets with no voids & get a consistent smooth bullet base when the sprue plate cuts the puddle. Along with clean full diameter, sharp edged drive bands I do this with all my aluminum 4 & 6 cavity molds, lee/mihec/neo).
Borderline frosting, an interesting term.
What this brings to the table is the timing/cadence of your casting to make an extremely consistent bullet. If you start out casting with a +/-675* alloy and a 2-cavity al mold that is producing shinny bullets and then 3/4 th's the way thru your 20# pot you have to stop because the mold got too hot. Then you've just cast a bunch of bullets that have differences in diameter/weight/voids in them. This is extremely common with 2 cavity molds.
It's 1 thing to cast blammo ammo & another to cast a quality bullet. Same alloy, same mold, just depends how you use them.
Sorry for being long winded but if you figure out what temp that brass mold likes to be run at when it produces borderline frosted bullets. You will end up with a pile of consistent weight/diameter bullets. A scale is your friend, do a casting session some time and grab 100 random bullets and way them. You can get down to +/- .3gr with a brass mold casting +/- 200gr bullets if you watch what your doing when cutting the sprue's (not tearing/divots) from a #20 pot of alloy.
Borderline frosted bullets 4-cavity brass
borderline frosted bullets single cavity nose pour steel mold. Note voids and wrinkles in the bullet bases, had to bump the pot up to 750* due to the huge hb pin/ pin ='s heat sink.
borderline frost 4-cavity brass
borderline frost 2-cavity brass This is that "ness" bullet that's extremely hard to cast with it's deep hp (30cal hp). The long hp pins ack like a heatsink making the noses shinny/wrinkles but the bullet bases/bottoms are frosted.
Borderline frosted bullets is the only real visual way to know where your mold temp is at. It will also point out any cold spots/heatsink areas of a mold allowing the caster to adjust their casting cadence/alloy temp/wait time before cutting sprues. It also aids in things like tumble lubing & pc'ing bullets. I also like to dry size frosted bullets, the shinny metal vs dull frosted metal has an excellent contrast and makes it a lot easier to spot defects in in the bullet or mold.
Good luck
