Getting Good Base Fill Pouring into a 4-Cavity?

[Grump]

I've tended to be pretty picky on my "Grade 1" boolits when sorting...which has sometimes had my production of my version of perfect as low as 1 in 10 bullets cast. Rounded corners on the base, I'm wondering if it's all okay if they are still round when looked at end-on. The question is, how "minimal" is minimal enough on the corner of the base. I tend to send them into "Grade 2" if the radius on that corner is about equal to what you'd get putting a round corner on a business card.

Sorry, I'm not calibrated to .001s on this and don't want to haul out the micrometer.

What's bugging me is that my last two casting sessions have produced a fair number of uneven-cornered base fills. Nearly a knife-edge partway around the base, then visibly rounded on the corner for 1/4 to 1/2 of the circumference.

I am pouring one cavity at a time, seeing the fillup spurt for a half-second then moving up the slightly tilted mould to the next hole. Try to get the liquidus in there fast, hold a second on the last cavity, and then pouring back away from me on the sprue to melt back off the sprue stuff. I was draining enough off on that last step a few days ago that the sprues came out as four separate cones rather than a bar connecting them all.

I run hot for a frosty boolit but leave the mould to cool long enough to avoid cutting out raggedy-bottomed sprue tear-offs, for lack of a better term. Today I left enough lead in the sprue to keep all the cones together, and even tried tilting the mould back towards me to reverse the tilt present during the pour, as I watch the sprue puddle solidify. That *seemed* to help the base fills a little bit but the 20 or so pours I did this on wasn't enough for me to make any firm conclusions.

So, I'm wondering if there are any tricks other than an ill-fitting sprue plate (thank you, RCBS on the one I sent in for service two years ago...easy enough to fix) to get a higher percentage of knife-edge boolit bases. Cramming the sprue plate up against the bottom pour nozzle seems to work with other moulds, but the 4-bangers with a gutter connecting the fill holes don't allow that.

By the way, my slightly relaxed "Grade 1" standards are producing loads that shot 3-1/2 inches at 50 yards. I'd LOVE to get them another inch or more tighter.

Thanks!

[bangerjim]

You did not tell us your alloy mix.....a big part of filling. Would help to know what you are using.

I would recommend 2% Sn. I use that and get perfectly square greasers and bases every time.

[country gent]

Several little things may help you out. You didnt state the mould or alloy so its a quick guess as to. One make sure all vent lines are clear and allow air to pass. An ice pick awl or scribe point lightly pulled thru the vent lines insures this and may even show dirt or crud build up. Sometimes a very light bevel stoned accross the blocks top mating edges helps with this also. Another thing is how tight is the sprue plate and how much pressure are you putting on it when filling? Start by cleaning mould good with dish soap and water and dry well. Look over for issues with a magnifying glass, look for small dings burrs or other issues. Drag a q-tip around edges of bocks cavities and or grooves edges look for pulled cotton fibers this indicates a rough area. Check bottom of sprue plate for build ups dings and scratches. Lightly stoning the top mating edges provides one last vent right at the base of the bullet. Break each edge with a very fine stone at 45* for a .005 flat. Darken edge with a marker, when you see a definite silver line your very close. Smoking moulds, mould release or other build ups can plug vent lines and restrict venting. Smoke under sprue plate can have the same effect.

[runfiverun]

I have found that the short fat boolits like to be poured into slightly slower this allows air to escape through the sprue cut off hole.
the long skinny ones seem to like the stream shot straight through the sprue hole right to the bottom.

[Tatume]

Sprue plate is not hot enough.

[Grump]

H&G 73 145-150 SWC. Alloy is mix of maybe 1/4 range lead, rest isotope container and I put about 1% more tin via solder when mixing it up. That might have been the second 1% sweetening. The SAECO says it's BHN 8 and it goes slushy when the Tel-Tru reads between 510-520 F.

Fillout is perfect everywhere but the base.

[Grump]

Sprite plate is hot enough I'm blowing on it to cool the alloy before striking it off. Bullet bases show light frost.

[Grump]

Mould is clean and no vent lines are compromised.

[Tatume]

Don't blow on it. Sprue plate is not hot enough. Keep it hot longer by over-pouring. If the bullet stays molten next to the sprue plate long enough the alloy will be able to migrate into the corner and fill out the base. If it gets too hot the alloy will fill out the vent lines, which is, of course, not good. But your alloy is not filling out the corner of the mold, because it is cooling too soon.

[JonB_in_Glencoe]

H&G 73 145-150 SWC. Alloy is mix of maybe 1/4 range lead, rest isotope container and I put about 1% more tin via solder when mixing it up. That might have been the second 1% sweetening. The SAECO says it's BHN 8 and it goes slushy when the Tel-Tru reads between 510-520 F.

Fillout is perfect everywhere but the base.

the above indicates that it could use this <stated by country gent> "Lightly stoning the top mating edges provides one last vent right at the base of the bullet."
...ALSO, pouring large as possible sprues helps keep the sprue plate hot and will help base fillout.

[runfiverun]

it is definitely venting related, I have seen square sharp corners accompanied by a little washed out spot on the base caused by venting issues and it's just cause the one cavity can't vent into the other.

[Grump]

JonB, that thought on a last vent line was trying to cross my mind last night. I did smooth the top of the blocks a few years ago, that might have narrowed the parting line channel a bit too much.

[Grump]

Okay, here's what I'm talking about. Curious about whether round (diameter) but rounded (heel) boolits suffer in the accuracy department.

Pretty round but rounded a bit in the heel:
153630


Not so round (actually a reject):
153631
In the widest parts, this one has better, sharper base fill than the prior photo.

How they look in the mould:
153632

This is after I stoned the top corner of the mould's parting line to obtain a "base vent" or whatever. The pours last time had far fewer really bad out of round bases, but a lot that were nice and square near the parting line but varying degrees of rounded 90° from there. The rounding is generally less pronounced that before.

From the last two sessions, leaving a puddle in the sprue channel seems to help.

[Cap'n Morgan]

It's a venting problem alright. If you try tilting the mold while casting I bet the round edge will form at the highest point of the cavities.
Try adding a few vent-lines diagonally across the top of the blocks using a needle file or similar (a checkering file works great) but don't go to deep - about .002 will do.

[Grump]

Yup, Cap'n, I have been thinking along those lines.

But now I wonder--vent the top of the blocks, or the sprue plate??? Considering all the possibilities.

[Cap'n Morgan]

Vent the top of the blocks. Otherwise you'll get an imprint of the vent lines (and perhaps a smear when opening)on the back of the boolits.

[myg30]

Sometimes to tight a spruce plate is worse than a real loose one.

Mike

[popper]

Venting and pour rate (too fast). I've had problems with the slotted sprue plate also, found pour each cavity & shut flow between - channel adds weight to sprue which hurts venting. Don't cool the plate and don't pour a big puddle. I broke the top edge of the 2x mould, you may need to scribe a vent BETWEEN holes & perpendicular to the block edge. I use Isocore with some Cu. Funny, my GC moulds don't have that problem. Yes, better bases will reduce group size.

[Grump]

Sometimes to tight a spruce plate is worse than a real loose one.

Mike

True that. I learned it with an RCBS two-holer that I sent back for some reason. It came back fixed, the sample casts that came with it were perfect, and then when the bolt worked loose I cranked that baby pretty tight.

THAT brought too good of base fill, like fins! Upon closer examination, I found that the mating surfaces of sprue plate and mould block were just enough off that cranking the bolt tight flexed the sprue plate up. I love solving problems...even when I made 'em.

[Grump]

H&G 73 145-150 SWC. Alloy is mix of maybe 1/4 range lead, rest isotope container and I put about 1% more tin via solder when mixing it up. That might have been the second 1% sweetening. The SAECO says it's BHN 8 and it goes slushy when the Tel-Tru reads between 510-520 F.

Fillout is perfect everywhere but the base.

Was mis-remembering the hash marks on the thermometer. The alloy slushes up about 580.

[mongoose33]

I was struggling with a 6-cavity mold--had incomplete fillout of bases in the cavities toward the handles, not so much at the other end.

Someone asked how I was filling them--I'd start at the end, and fill toward the handles. Problem turned out to be that the handles were drawing heat off the mold, and on the handle-end it was too cool.

The answer was to start filling on the handle end, which kept it hotter as the boolits stayed in there longer. You might also consider changing the direction you fill the mold, and make sure you have a generous sprue puddle.

[Grump]

Have added transverse vent lines on the top of the blocks, haven't cast with it yet.

In the meantime, I finally tested from a nice rest, 6-inch revolver and red dot sight.

My "Grade 1" boolits shot into like a 4-inch group. Marked with the golf tees in the first pic.
154198
Then my "Reject" boolits like the ugly base pictured earlier put 4 out of 5 shots into an inch, exactly. And one flyer only about three inches out. That's at 50 yards.
154199
I think they were the testing rejects and not just Grade 2... Yes, I do understand that this could just be the statistical fluke, outlier, or whatever you want to call it.

I may be regretting the stuff I loaded up earlier this month.

[Grump]

Always possible, Popper. The bags were marked, but there's that possibility that I shot them in the wrong order. Or something. More testing...

[shredder]

I have found that the short fat boolits like to be poured into slightly slower this allows air to escape through the sprue cut off hole.
the long skinny ones seem to like the stream shot straight through the sprue hole right to the bottom.

++1 on the long skinny method. Rounded bases until I poured them like this. Straight down the hole full throttle from the bottom pour. 2% tin makes a difference as does the sprue puddle. Be generous, this lets the boolit "pull" metal to fill out as it hardens.

[gwpercle]

I too am a stickler for the perfect base and darn near perfect fill out everywhere else on the boolit. I just like perfection and the only way I can get it is to "pressure cast" with the spout of a Lyman ladle pressed to the sprue hole , held sideways, then quickly turned up right , hold for a count of two, and leave a generous sprue puddle on the hole. Holding the sprue hole up to the spout of a bottom pour pot should produce the most pressure...but for me it only produced more rejects.
You might just want to try the spouted ladle pressure cast method.
Gary

[Grump]

Well, the control key when I should have pressed Alt just ate my update post.

Didn't mix up the boolits for sure this time. Reject boolits with bases that looked not really round when viewed from the rear (a little rounded here, nice square base there) shot about 4-1/4 or so (spanning the middle of the 9-ring) at 50 yards. Cases sorted by headstamp, no super-bad ones with sections of the base just not there.

"Grade 1-" or "Grade 2+ boolits shot as good as anything else so far--2.4 inches at 50 for the 4 that were all Remington, then the last shot in a Star Line case that sneaked in there hit low from the group. Horizontal spread for all 5 was easily X-ring. Some of these were noticeably rounded at the base but all had the flat part of the base looking round. The rounding would measure about like putting a rounded corner on a business card.

Cleaning up the mould, I noticed that this H&G unit is a tiny bit higher between the cavities, and lower 90° from the parting line. This would create a sort of vent in that direction. But in cleaning up lead smears over the years, it looks like I took enough thousandths off to close that gap too much. Will tweak it a bit more before the next session. The parting line vent actually resulted in several boolits that were perfectly square and sharp near the parting line (call that 12:00 and 6:00), then gradually picking up a trace of rounding at 9:00 and 3:00. So long as they are symmetrical, they shoot just fine. So that's where better venting needs to be restored.

Even though it appears I've been a little too picky in selecting my "Grade 1" boolits, I'll still seek more perfect base fill just because I like it.

[popper]

Now look for non-perpendicular bases.

[sparky508]

Arent you concerned those golf tees will foul your barrel? :kidding: