Mi-Hec procedures

[wv109323]

Tell me what I am doing wrong. I have a Mi=hec 360158 SWC 4 cavity mold. Mold is flat base and solid point. I cast with it last night and really did not do very well. Pot is a Lyman 20 lb. with a PID control. Lead is range scrap from a Bullseye pistol range.
Temp. was set at 700. Mold was pre-heated on a hot plate. I could not get a nice square corner on the base and the edges of the crimping grooves and grease grooves were rounded and frosted on a lot of the boolits. I cast for about 1 1/4 hours and had around a 50% reject rate. It took quite a while for the mold to start to produce acceptable boolits, like the mold was not hot enough. The first boolits were wrinkled. The mold was on the hot plate a good 15 minutes before starting to cast.
After quitting with the Mihec, I started casting with a RCBS 358 - 158 gn. RN. Bullets were almost immediately acceptable and a very low reject rate. I cast more "keeper"RN boolits in 30 minutes with a 2 cavity than I did with the 4 cavity.
Weighting the bullets today showed the RN were much more consistent weight than the 360158 Mihec. The RN were 156gn to 154.5gns. The 360158 were 155.0 to 151.0 for the keepers.
What needs to be done to cast equally well with both molds.

[seagiant]

Hi,
Just a thought,but alum. and brass like a hotter temp on the lead than iron molds!

[tomme boy]

Turn your lead up to 725* Put a little more heat into the hot plate. It shouldn't take anymore than 1-3 pours before you get good bullets. Brass is a pain in the rear to get used to. And they wear you out a lot faster. I can cast for 3-4 hours with a alum mold. 1-1.5 with a brass.

[longbow]

I like my brass moulds but as stated, they like to run hot... not just hot alloy but hot mould. Don't fiddle with or inspect boolits when they drop, get into a fast steady pouring rhythm and the boolits should come out nice. You have to keep the mould temperature up by casting steady.

As for pre-heating, I pre-heat until the sprue plate lube just starts to smoke. At that point the mould is actually a bit too hot and it takes a few pours to settle in then the sprue puddle hardens in a few seconds and I am good to go.

Another issue may be fluxing. I use a lot of range scrap myself and find that I need to flux regularly to keep lead clean and pouring going well.

That's what works for me anyway.

Longbow

[GLL]

The suggested addition of heat is good but you might also consider adding 1% Sn to the pot as an experiment !
Range lead is often deficient !

Jerry

[Forrest r]

Sounds like the mold wasn't hot enough.

I use a hotplate to pre-heat the molds, the hotplate has a dial with the #'s 1 thru 6 on it. When pre-heating molds the hotplate gets set a little over 5 (6 is max) & I leave the mold to pre-heat until they get hot enough for the molten lead to stay puddled on the sprue plate to a count of 9 or 10.

The mold will be too hot @ this point, the bullets will frost. But it's easier to leave the mold open for 10 to 15 seconds & try again slowly cooling the mold down than it is to keep pouring bad boolits trying to heat the mold up. It usually takes only 2 or 3 tries at leaving the mold open for 10 to 15 seconds & it will cool down and settle in producing beautiful boolits. After that it's just a matter of establishing a cadence for the mold/alloy temp to keep producing quality bullets.

I was a little leery of pre-heating these molds up that hot at 1st, didn't want to warp/ruin then. But now after owning 11 mp molds they all get the same pre-heating treatment.

Actually I just went thru the same thing with my 1st noe mold (what a work of art!!!!) & didn't want to over heat it trying to pre-heat it. I was casting garbage @ 1st & then treated it like the brass mp molds & set the hotplate a hair over 5 & pre-heated the mold until the lead puddled on the sprue plate for around 10 seconds before the sprue solidified. After that I left the mold open for 10 to 15 seconds between pours until it cooled down & settled in. When it did that mold made a mountain of boolits in a hurry.

[Echo]

I run my MP 45HP 4-banger on about an 11 second cycle - drops perfect boolits every 11 seconds.

[wv109323]

Thanks for the answers. I will try a hotter mold and bump the lead up to 725.. The lead on the sprue plate was solidifying in about 4-5 seconds.

[GMT210]

I have found the best cadence is to run two molds, at 725 degrees plus preheat. Here's the seqence from the very beginning
1. Pour 1st mold
2. Set down 1st mold
3. Pour 2nd mold
4. Set down 2nd mold
5. Open 1st mold, re-fill, set-down
6. Open 2nd mold, re-fill, set-down
7. Open 1st mold, re-fill, set-down
8. Open 2nd mold, re-fill, set-down
9. Repeat until pot is empty

[dmize]

I have 7 Mi Hec Molds.
I get my alloy up to temp. I then put far corner of mold in the alloy until it comes out clean. I then kick the sprue plate out and dip it until it comes out clean. Then I start casting dumping the first 2 casts back in the pot.
Just make sure you don't get the pin ends in the lead. lead gets in the c-clips and gets to be a pain to get out.
I have done this to all of mine,some are 4 years and thousands of bullets cast and everything still works perfectly.

[Minerat]

This may not be the place to ask the questions but . . .

Can not having a brass mould hot enough cause a casting to be oversize?. Not much just .003 but that causes the GC shank (0.398) to be 0.012 less then the sized drive bands (0.410) putting it marginal for a thin 410 Gator gas check. I have cast about 300 good bullets with it and rejected another 100 or so. It has thrown some frosted so bad as to be rough, which I think means the mould was tooooo hot and some with poor fill out probably not hot enough. Alloy is a 10:1 (WW to tin). The overfill is getting solid at around the 5 count and the pot is a bottom pour running at 7.5.

My concern is because this is the second 412640 mould Mihec has sent and I am getting the same oversize castings from both moulds. I am beginning to get the feeling it is operator error since this is my first mould and if it is I owe him some money or at least return one of the sets of blocks so he can re sell them.

Is it possible to put the GC on before sizing and possibly swaging it to the shank?

Am I over thinking this?

Thanks,

[tomme boy]

You are supposed to put the check on before you size the bullet. Are you saying that you size the bullet then try to put the check on? If you are doing it that way, That is your problem that they are not fitting.

[osteodoc08]

Put the GC on then size. The GC will grab on and stay on assuming everything is as it should be dimension wise.

[Old School Big Bore]

Did you scrub the mold first? They do need degreasing with either hot soapy water or some residue-free solvent. If that doesn't do it then by all means try a bit of tin in the alloy. Good luck.

[dragon813gt]

Here is the biggest tip I can give when it comes to brass molds. The molds like to be run hot. Lead temp doesn't play much into this. Preheat the mold on a hotplate to the point where the bullets are coming out frosty. Then you know the mold is up to temp. I usually run the lead around 725 degrees but this isn't that much higher than w/ other molds.

The other thing about brass molds. They get better w/ age. I have a higher reject percentage w/ new molds. They are cleaned w/ 2+2 when I receive them. Heat cycled three times in a toaster oven. Taken apart and fully lubed. Then I start casting w/ them. By the fourth casting session the reject rate is virtually zero.

[Minerat]

No I haven't got gas checks yet. It started when I asked Blammer which of his checks would work with the mould. He suggested the .416's but ask for the shank size as cast. This is 0.398 or about 0.005 over the listed 0.393 max shank size for that size GC. The thinner .410 GC's still call for a shank max size of 0.397 so I am still over by 0.001. If I get the thinner GC's, install and then size I'm concerned there may be a problem with the GC being damaged since I will size a .014 GC on a bullet with a shank - drive band difference of 0.012. In other words it will be 0.002 bigger then the drive bands unless they would swage into the bullet.

I have cleaned the moulds using WD 40 and a tooth brush first then followed with brake cleaner and a toothbrush. It throws great bullets once it reaches temp. I have found that preheating makes a difference on fill out but still have this oversize problem.

I did not heat treat but the mould have been used 5 times and I did 2 heat/cool treatments tonight to see if that makes a difference. I am not really having a problem with a lot of rejects just a concern with the oversize problem I explained.