Mold help/advice pls

[oscarflytyer]

Have an RCBS 2c 45-255-KT. Estate sale acquisition. Cast with it last night first time. I know it’s a good mold/perfect condition – the estate sale lot had a lot of classic and old molds…

For the life of me, I can’t get this one to fill out the back cavity well consistently. I cast 150-200 bullets, and only 60 passed inspection. The front cavity is great. Back cavity is the offending member.

I was using WW+2% tin (and right behind this problem mold/same alloy, etc, I cast 200+ perfect Saeco 453 45 WCs!) . Pot was started at 685 deg, eventually cranked all the way up to 785 deg! Bullets never got frosty (as I would expect at that high temp).

I ladle cast, and was “force pouring (can’t recall correct terminology)” the mold – ladle spout directly into the sprue plate. Worked great on the front cavity, but the back cavity – zero consistency.

Back cavity bullets tended - prob 70% of the time - to have the base band rounded/not filled out/soft edges, sometimes into the next forward band.

What am I doing wrong/missing?

 

[JustJim]

If you only pour in the back cavity, does it fill out? I bottom-pour, and have had a couple of RCBS moulds that wanted the back cavity filled before the front cavity. Since that worked, I never went looking for the "why?".

 

[oscarflytyer]

If you only pour in the back cavity, does it fill out? I bottom-pour, and have had a couple of RCBS moulds that wanted the back cavity filled before the front cavity. Since that worked, I never went looking for the "why?".

"If you only pour in the back cavity, does it fill out?"

not yet! BUT!... And I REALLY want this one to work. Can't get it new, and nothing close, plus it drops ~.453+ - exactly what I need!

Thanx

 

[RBHarter]

Check the sprue plate it maybe bent , twisted etc . Don't ask because honestly I don't remember what mould or moulds it was but I had one or more that acted like ths and had burr that held it up , pinched the other end , and messed with the block vents .

Check the block vents . I had one or more of those also .

If all else fails carb or brake cleaner then a bath in Dawn old skool blue and hot hot water .
There might be some oil or something that just has to work out and burn off . I've had that happen once too .

With 50 pours it should have been plenty hot .......but did you pre heat it ?
Did you get it hot enough for alloy to.not stick to the outside, "dip the corner" ?
You said you pressure poured . But did you dripping the sprue or a bump before the sprue cooled ? It's weird but I have one like that too along with the swirl pour and the drop straight through the center as fast as it'll fill . Also the one that wants 13524, 24135 ,12345 ,54321 , repeat.

 

[Bret4207]

Try something other than pressure pouring. I have moulds that demand spout to sprue hole contact, a 2" off center drop or a 1/2" dead center drop. Others don't care at all what I do as long as the mould is hot. Spout to sprue plate and junk castings sound like a venting issue- try lifting the ladle spout to let the air escape.

 

[Dusty Bannister]

A good cleaning sounds to be in order. Perhaps a little lube on the sprue plate screw has migrated into the cavity and just needs to be removed.

 

[CWLONGSHOT]

Also look at the venting maybe ya have some build up blocking air flow.

CW

 

[Ben]

Have you taken a fine cut flat file and slightly broken the top edges of the mould. Can make a big difference. Will the sprue plate swing of it's own weight back and forth. A good cleaning and checking for venting is in order.

Ben

 

[oscarflytyer]

Thanx guys for all the help! I def want this one to work. I will relook/clean/try dome things. May even be as simple as how I was pouring it...

 

[Ian]

Ben, JustJim, and Brian give good advice. I have lots of moulds that like the back cavity filled first even after all the other tricks mentioned have been done.

 

[BudHyett]

Being possibly an older RCBS mold, this may have the thin sprue plate. These are not conducive to heat retention which slows the pour and prevents fill. If you have a newer RCBS mold with the thicker sprue plate, switch the sprue plate for a trial.

 

[fiver]

just pour the alloy in that hole. [not match and turn]
i bet your either not quite hot enough on the plate or just don't have enough venting.
probably both.
but simply pouring [allowing more air out] and heating the base more will generally fix what your describing.

 

[oscarflytyer]

I had it hot! interestingly, even at 785 I couldn't get frosty bullets. That surprised me.... Reading through suggestions, I am thinking maybe I simply was sealing off the air escape. And, the more it wouldn't fill out, the more I pressure poured. Guessing I simply went the wrong direction! This one will get another chance. I REALLY want it to work. I want to feed my Redhawk Colt with it!

 

[358156 hp]

I had it hot! interestingly, even at 785 I couldn't get frosty bullets. That surprised me.... Reading through suggestions, I am thinking maybe I simply was sealing off the air escape. And, the more it wouldn't fill out, the more I pressure poured. Guessing I simply went the wrong direction! This one will get another chance. I REALLY want it to work. I want to feed my Redhawk Colt with it!

Try picking up the pace a bit and cast faster to get the mould up to proper temp. You may simply be not getting the mould hot enough. I've also had initial issue with getting the sprue plate hot enough to allow air from the cavity to purge.

 

[Bret4207]

I had it hot! interestingly, even at 785 I couldn't get frosty bullets. That surprised me.... Reading through suggestions, I am thinking maybe I simply was sealing off the air escape. And, the more it wouldn't fill out, the more I pressure poured. Guessing I simply went the wrong direction! This one will get another chance. I REALLY want it to work. I want to feed my Redhawk Colt with it!

The mould was 785 degrees or the pot? Remember that pot temp has just about zilch to do with mould temp.

 

[oscarflytyer]

The mould was 785 degrees or the pot? Remember that pot temp has just about zilch to do with mould temp.

Pot. And I was casting as fast as I could to keep mold temp up. I honestly beleive it was probably technique and just need to let the air escape.

 

[Ian]

Tale of Three Bullets

All cast from 690⁰F straight clip-on wheelweight alloy with very little (about half a percent) tin present. Left to right: Mould too cool, mould just right, mould to hot. You don't need tin or 800-degree alloy to get perfect fillout. Just sayin'.

www.artfulbullet.com

 

[PED1945]

Being possibly an older RCBS mold, this may have the thin sprue plate. These are not conducive to heat retention which slows the pour and prevents fill. If you have a newer RCBS mold with the thicker sprue plate, switch the sprue plate for a trial.

Back in the early 80s I made a thicker sprue plate for my RCBS 2 cavity 44-225 SWC GC. It has been working fine since then. Do not recall how I learned a thicker sprue plate would help.

 

[358156 hp]

If I'm casting in a cold garage I often turn the sprue plate 90 degrees to the block and preheat it by dipping about an inch or so into the melted alloy. This is especially handy with heavy sprue plate on 4 cavity MP moulds.

 

[BudHyett]

Pot. And I was casting as fast as I could to keep mold temp up. I honestly believe it was probably technique and just need to let the air escape.

When using a bottom pour I set the handle down to where when opening, it starts to dribble. Then I back it up to where I am getting the first full stream. This allows the mold to fill and the air can escape out the top because the top is not completely closed by the lead stream.