Troubleshooting a mould - opinions requested

[martinibelgian]

Dear group,

I have a .458 540gr mould which I use for BPCR. It casts a nice-looking and very accurate bullet, but is rather hard to work with... I have to cast in a really narrow temp range with both mold and lead, or I get some lead between top of the blocks and sprue plate around the bullet base (yes, a base pour mould).
This is the 1st mold giving me this problem, and I would like to know what I can do to cure this situation.
I'm not really new to bullet casting, I've been casting for about 10 years, mostly large , heavy .45 cal bullets for BPCR shooting. I managed to get all my moulds tuned up, but this one is giving me fits.

I already tried polishing both sprue plate and top of the blocks with emery paper on a flat surface, running it with a tight and a loose sprue plate - no ceegar. The base of the bullet regularily gets 'flashing', more specifically some lead flow from the base of the bullet between the sprue plate and the top of the blocks.
My question is - what can I do to remedy this? Any and all expert opinions and advice appreciated. would this be a venting problem maybe?

[leftiye]

Yer sprue plate is either loose, or the hold down screw/spring thingie is out of adjustment (too tight sometimes does this), or maybe there is something on the mold top surface that is holding the sprue plate up (lead adhesions, or a burr, bent sprue plate, non flat mold top surface, etc.). I like the sprue plate to be just tight enough that it doesn't flop around, and I put flat washers under the head of the hold down screws and lose the springy ones (fling 'em). You also need to determine that the sprue plate is straight and that it is possible for it to lie flat. If you can't get it to lie flat (without light showing thru the crack) you'l need to stone the surface of the mold, and sprue plate, or maybe hammer the sprue pate some (carefully - no dings).

[e15cap]

I have seen the same thing and the way I cured it was by decreasing the amount of lead in my dipper. The weight of all that lead rushing into an empty mold will push it into the gap between the sprue plate and the mold and turn those nice bases into rivets. I also reccomend everything leftie said. Best Roger

[montana_charlie]

If lead can get between the mould top and the sprue plate, so can air. That should eliminate 'venting' as the problem.

Check the corner of the sprue plate where the pivot hole is. Make sure the corner isn't bent upward. That could hold an otherwise nice flat sprue plate off of the mould top.

That's one place where leftiye's hammer could come into play...

CM

[runfiverun]

try pouring from tthe ladle, not pressure feeding it
or try a new sprue plate if ya got one.

[leftiye]

The hammer thang was used on a couple a curved sprue plates - worked too! (the sprue plate only has to contact the top edge of the cavity to work) I've seen molds where the corner of the mold where the pivot screw for the sprue plate is was lower than the rest of the mold top (maybe a less good use of the hammer, or worn from long use when too tight). Tightening the screw down held the sprue plate up off of the mold. Very often a loose sprue plate will cast well, even if flopping around. Sounds to me like the mold in this present discussion has space between the plate and mold, and that when the temp gets high enough, lead runs in there (maybe).

[martinibelgian]

Well,

Taking into account he comments posted here, I took the mould completely apart and did following:
Polished the underside of the sprue plate with 600 grit emery, I apparently got nice and uniform contact (no wobbling), so I presume the sprue plate is straight.
Did the same to the top of the blocks to smoothen everyting out, and make sure there's no burr on the pivot hole
Re-fit the alignment pins
Adjusted the sprue plate till it barely swings under its own weight without slop and I couldn't see any light between top of the block and bottom of the sprue plate, then tightened the lockign screw down
Put a (brass) washer between sprue plate and sprue plate screw

Unfortunately, I won't have time to test it today, that will have to wait till next casting session...

[MtGun44]

My bet is that you have fixed it.

Bill

[ed etheridge]

i would put some machinests blueing on the sprue plate and top of mold. when dry try lapping on flat surface that will show you any low spots. i have coated top of mold with graphite by rubbing pencil on surface this will help keep the lead from adhering.

[Calamity Jake]

Now that you have it cleaned up, get you some "Bullshop" spru plate lube, use per directions and never have to worry about it again.

[carpetman]

Martinibelgian----You have a mold which you use for BPCR that is giving you trouble. I guess to use the mold for BPCR you are throwing it down range? Probably messed something up doing that.

[IcerUSA]

Only other thing I can suggest is after the mould is up to temp , check the sprue plate to make sure you still see no light as the sprue plate might have stress in it and warp a little from the heat and when it cools it is flat again.
If it is flexing from the heat I would heat it red hot to stress relieve(anneal) it . So to speak .

Keith

[Jon K]

Sounds like you have it well fitted, now get it up to temp, apply Bullplate Sprue Lube, follow directions, use sparingly. Works Wonders..............

Jon

[martinibelgian]

I have the bullplate stuff (Received a sample with a Steve Brooks mold) - but the mold at this moment is at my gunsmith's, he wanted to try a few bullets with his alloy. So he actually is testing it for me today... We'll see what he has to say about it - if it still has issues, and he gets fed up with it, it just might have a new sprue plate when he returns it!

[martinibelgian]

Just got back a report from my 'mith, he just loved the mould, liked the way it cast and dropped the bullets. Never even mentioned any finning under the sprue plate - so I believe I can conclude that he problem has been solved. Thanks to all who have given me information!

[martinibelgian]

Update - I cast 100 bullets this WE. This mould needs to be run HOT and FAST (about 450 celsius), but the results are pretty consistent - I get a ES of 0.8 grs for an average 541.6 gr bullet - everything is between 541.2 and 542, only 3 rejects - which I presume were caused by me taking a break to let the pot come back up to temp when adding some ingots... And, no flashing anymore! I did use the Bullshop sprue plate lube, but moderation is the word here - a bit too much, and you are getting base fillout problems. I believe that little vial will last me a loooong time...

[dubber123]

Update - I cast 100 bullets this WE. This mould needs to be run HOT and FAST (about 450 celsius), but the results are pretty consistent - I get a ES of 0.8 grs for an average 541.6 gr bullet - everything is between 541.2 and 542, only 3 rejects - which I presume were caused by me taking a break to let the pot come back up to temp when adding some ingots... And, no flashing anymore! I did use the Bullshop sprue plate lube, but moderation is the word here - a bit too much, and you are getting base fillout problems. I believe that little vial will last me a loooong time...

Glad to see you fixed it. :drinks: You are right about the Bullplate, it's VERY easy to over do it, and it takes FOREVER to clean itself out of a cavity. It works great with just the right amount though.

[Dale53]

Bullshop Sprue Plate Lube:

I was a fairly early "adopter" of this fine (should we say, "Wonderful" product). I have found the best way to limit the amount used to the "correct" amount is to use a method that someone on here suggested. When you are ready to apply the lube, shake the bottle. Remove the lid and just use the amount left in the lid from shaking. Use a que-tip and NOW you will NOT have too much lube on the que-tip.

MartiniBelgium;
Happy that you have your mould problems solved. About sixty years of casting has left me with the impression that BPCR bullets are the most difficult of all to cast. I shot BPCR Sil for about fifteen years and learned that if you can cast GOOD BPCR bullets you can cast ANYTHING! I consider +or- .6 (six tenths) of a grain is good work. My schuetzen bullets are cast+or- .2 a grain (but the schuetzen bullets are nominally 200 grs whereas my .40 caliber BPCR bullets are 420grs +). At any rate I do NOT have any accuracy problems with my BPCR bullets at my "standard". Incidentally, my "standard" applies to a four cavity NEI mould that does WONDERFUL work.

Dale53

[martinibelgian]

Dale,
If there's 1 thing I have learned, then it's that for BPCR bullets, a mediocre mould will cause lots of frustration... You need to be repeatable, so bullets must drop out reliably with minimal manipulation, allowing you to keep your casting cycle the same each time. Then again, not all moulds are equal, and I do have to admit that this one is the 1st BPCR mould I have that needs such a rapid pace and high temp - most need more time to perform best, or will overheat and give other problems. Ah well...
And yes, casting the smaller bullet (like the 120gr heeled RN for my cadet) is extremely easy when compared to these big hunks of lead. I presume we do it for the challenge! :-)