Sprue issues

[Rob Lynch]

Hey guys, need some help!!!! I am having a hell of a time getting my 45 caliber bullets to cut a smooth base. I end up with a divet that looks torn or a protruding Sprue and still looks torn. This is a Iron block Accurate mold. I am using 20-1 alloy from Buffalo Arms and running it at 800 degrees, I also pre heat my molds using Idaho Lewis's method with 2 MR Torch heads. Mold and sprue plate are definitely hot and they will dance about 45 seconds on my first fill out then they settle in. I fill 5 before I start closing the plate for keepers I get great fill out and crisp edges, but I just can't get this one to cut clean. I have tried waiting from 1 to 2 seconds to 30 seconds in 5 second increments after the sprue frosts over. I also leave a very large sprue pour on the plate when casting. I tried running the sprue plate loose and tight to the point I get small voids in the base from having it to tight. The bullets are dropping from the mold very consistent on weights as well. Less the 1 grain difference is normal. Been fighting this one for a few weeks now. I attached a few pictures for reference.

 

[bronko220002]

How accurate is your thermometer? I was getting the same thing with what looks like the same bullet (.458, 500 gr Lee mold) I was casting at 725*. I boosted my temp up to 800 and they came out perfect.

 

[Rob Lynch]

How accurate is your thermometer? I was getting the same thing with what looks like the same bullet (.458, 500 gr Lee mold) I was casting at 725*. I boosted my temp up to 800 and they came out perfect.

Thanks for the response Bronko, that is a very good question, its a Roto Metals temp gauge. I know that doesn't mean anything, but would have to get another to find out. I guess I could try a bit more heat and see if it changes anything.

 

[bronko220002]

Thanks for the response Bronko, that is a very good question, its a Roto Metals temp gauge. I know that doesn't mean anything, but would have to get another to find out. I guess I could try a bit more heat and see if it changes anything.

You're welcome Rob. Another thing I do is, because its a big bullet, I cut/open the sprue as soon as it solidifies then wait about 20-30 seconds and dump the bullet. The sprue looks more like a "smear". Check out Lewis' "another casting tip (building up a good sprue)" below.
Be sure to drop the bullets onto a padded surface. In the bottom of a small box I place a folded T shirt then a square of leather from an old possibles bag and drop them in there. Don't drop those big bullets in water. I tried that once and they actually bent slightly and had to be recast. I didn't know it until I did about 200 of them! Lesson learned.

 

[michiganmuzzy]

X2 on more heat. Also, if it’s only happening on that one mold you may try to sharpen the sprue plate cutting edge with a couple strokes from a knife sharpener or stone, and/or polish the underside of it. Its definitely smearing the lead a bit. Are you finding it harder to open that sprue plate? loosen it a bit and see if the lead is sticking to it. Maybe even try smoking the sprue plate if it looks like its sticking to the lead.

 

[Rob Lynch]

You're welcome Rob. Another thing I do is, because its a big bullet, I cut/open the sprue as soon as it solidifies then wait about 20-30 seconds and dump the bullet. The sprue looks more like a "smear". Check out Lewis' "another casting tip (building up a good sprue)" below.
Be sure to drop the bullets onto a padded surface. In the bottom of a small box I place a folded T shirt then a square of leather from an old possibles bag and drop them in there. Don't drop those big bullets in water. I tried that once and they actually bent slightly and had to be recast. I didn't know it until I did about 200 of them! Lesson learned.

Bronko I turned up my heat so now on my Thermometer it reads 900. Definitely made a difference so possibly my gauge is off. I ordered another Thermometer and will compare it to my other. Things Definitely went better and I started cutting the Sprue as soon as it see stop moving. Then held the mold for 10 seconds and dropped the bullet. I do use a nice soft towel to drop into. My cuts do look better now.

 

[Rob Lynch]

X2 on more heat. Also, if it’s only happening on that one mold you may try to sharpen the sprue plate cutting edge with a couple strokes from a knife sharpener or stone, and/or polish the underside of it. Its definitely smearing the lead a bit. Are you finding it harder to open that sprue plate? loosen it a bit and see if the lead is sticking to it. Maybe even try smoking the sprue plate if it looks like its sticking to the lead.

Thanks for the reply, I do run my sprue plate till it will fall under its own weight. I have my molds for my 50 and haven't had this issue before with them. I understand different molds like difference things, but I exhausted every I knew first. So glad the community is here. I will check my sprue plate for sharpness and try dressing it with my diamond stone. I do have some smearing on the bottom of my plate.

 

[Rob Lynch]

Are the small voids around the sprue going to effect accuracy? I understand that the base is the rudder and what steers the bullet. My goal is to shoot my casts to 600 yards or more. So, far my Paper patch bullets are working for that, but really want to accomplish this with something I casted.

Rob

 

[michiganmuzzy]

Thanks for the reply, I do run my sprue plate till it will fall under its own weight. I have my molds for my 50 and haven't had this issue before with them. I understand difference molds like difference things, but I exhausted every I knew first. So glad the community is here. I will check my sprue plate for sharpness and try dressing it with my diamond stone. I do have some smearing on the bottom of my plate. View attachment 31394

It might help a lot just to keep that plate cleaned off. The lead on it could be exaggerating the problem too. I would definitely scrub that with steel wool and polish it a little. On some of my bullets that dont have a perfect base ive rubbed them across a piece of wood a few time to dress up the sprue, if its a little high from a loose plate. Ive also heard of people drilling a little bit into the base to dish it out a bit, to help with obturation(an interesting experiment maybe). But i think a clean and polish on that plate will make a big improvement.

 

[michiganmuzzy]

Are the small voids around the sprue going to effect accuracy? I understand that the base is the rudder and what steers the bullet. My goal is to shoot my casts to 600 yards or more. So, far my Paper patch bullets are working for that, but really want to accomplish this with something I casted.

Rob

I don't shoot those kinds of distances but everything I've heard and read leads me to believe it will affect accuracy noticeably out there.

 

[Rob Lynch]

Good read and I appreciate the time. I figured it might effect it, but didn't know to what extent. I am new to Muzzle loading long-range shooting, been shooting CF for years at that distance or more. It has been a great learning experience thus far. I found my stone and will polish it up a bit.

Rob

 

[HC]

How are you pouring? Ladle, compression, bottom pour ( distance between mold and spout)?

 

[white eagle]

try some sprue lube
should take care of it toots sweet

 

[Rob Lynch]

How are you pouring? Ladle, compression, bottom pour ( distance between mold and spout)?

HC, I am using a bottom pour pot, I start the pour with mold married to the spout and pull it away as it fills. I watch for the over flow and cover 80% of the top plate before moving the mold away.

Rob

 

[Rob Lynch]

try some sprue lube
should take care of it toots sweet

White Eagle, I wondered about this as well. I haven't used any before previously so Will need to acquire some.

Rob

 

[bronko220002]

try some sprue lube
should take care of it toots sweet

NOOOOOOO.....most mold manufactures do not recommend any lube on their molds other than the guide pins and the sprue pivot screw. And then they normally recommend beeswax.

 

[white eagle]

Never heard that one
some mold makers, like Miha at MP Molds sends it with the mold
that is why I have numerous bottles of the stuff

 

[michiganmuzzy]

Never heard that one
some mold makers, like Miha at MP Molds sends it with the mold
that is why I have numerous bottles of the stuff

I would be interested in knowing what it’s made up of. I was going to suggest, if nothing else worked, wiping a tiny bit of synthetic 2 cycle oil on the sprue plate, after cleaning it of the old lead smear.

 

[Rob Lynch]

Thanks for the comments guys, its definitely getting better once I ran a bit hotter as well.
Bronko I confirmed my temp guge today with another unit and they are both within 10 degrees of one another.

Rob

 

[Rob Lynch]

Now this maybe a dumb question but since I am still newish at it here we go. I decided to clean my pot out today. When I started filling my molds out I noticed that I was getting some chunky looking material in it. I spooned it out and put it in this pan. Is this just garbage or is this part of the alloy?

Thanks
Rob