How Much Shrink Inside a Cast Bullet?

[mfraser264]

Having spent many, many years in the commercial casting business with 3 different casting processes, they all share this common issue, shrink. Not dimensional shrink but volumetric shrink.

Most elements expand as they melt and shrink when they solidify. Take a 1 inch cube of solid aluminum and make a simple sand mold with it. Melt the 1" cube and pour it into the mold, all the molten metal will not fit.

For example, in steel casting, we poured 50 pounds to produce a sound 25 pound part.

As metal begins to solidify, it starts with the surfaces of the mold it contacts first and draws to the middle of the section. While solidifying, it is pulling molten metal to the solid metal. If there is none or not enough liquid metal to pull from, internal pockets develop called “shrink”. It shows up easily in X-ray and the only simple means for us Lead Casters to detect the shrink, well, most likely is weight. Casting tubes and cylindrical parts are not easy in industry or in Cast Boolits!

Before I forget, casting metal too hot usually does nothing but create more shrink. Cast as cold as you can and keep the mold temp constant.

This is also why the pool of metal on top of the sprue plate draws down and in, called "suck in" in some foundries. The center is solidifying last and looking for more metal to draw from.

One "Rule of thumb" in the casting industry is that a ratio of 1:1 is preferred when designing a casting. In other words, larger diameter, shorter boolits will be easier to cast provided you can fill the cavity fast enough. Long, narrow designs of boolits are difficult to cast. Most shrink will be in the base of the bullet most likely from the midsection to the base.

Shrink will impact accuracy as the tiny shrink pockets will throw the weight off and as the boolit spins, it will spin off center and more in an orbit rather than in a line.

One thing that would help reduce shrink is to provide more metal than what the mold can hold. One simple fix is to make a sprue plate thicker and hold a small reseviour (called a “riser” in the industry) for the base to have more metal as needed. I have thrown around a few designs and it can be done but haven’t cut chips yet.

So, has anyone ever wondered how sound/solid the cast bullet is? A sound/solid bullet is an accurate bullet!!! Would like to hear what you have experienced. If this seems a little technical, this is the engineer in me trying to figure out how to do it better.

[geargnasher]

Casting technique (basicaly the 'way' you fill it), mould temperature, alloy temperature, and size of the sprue puddle all have a profound effect on little voids in the bases, and thus accuracy as you mentioned. Using a Rowell-type ladle and contacting the sprue plate with the spout to make a seal so the lead can flow in with a little "head pressure" behind it and then breaking away and making a sprue puddle the instant the cavity is full is a good way to help prevent casting voids.

Many of us weigh our boolits where accuracy really matters (competition and hunting mainly) and there is almost always a few percent that are underweight by a half a grain or more, usually indicative of hidden voids.

The use of alloy containing arsenic or alloy that has been treated with sulfur seems to be less susceptable to internal voids, I'm not sure why, but I have a theory and my underweight percentages are definetely lower with such alloys. Sulfur and arsenic are "grain refiners" in lead alloy, my theory is they help the alloy "flow" better and "suck in" extra metal even as certain components of the alloy are freezing before others (with wheel weights, the antimony freezes first if memory serves, followed by the intermetallic antimony/tin bond if there's any tin present, followed by the remaining lead). Part of the problem with lead is that it forms large dentrites as it freezes and the coarse structure tends to clog up the whole object being cast so it forms more internal voids as it fully shrinks and cools. With the addition of the grain refineres, it remains more fluid as it's cooling so it can draw more volume from the sprue puddle.

Gear

[stubshaft]

That could be the reason for small voids to form in boolits. I usually pour a rather large sprue ala Veral at LBT. His sprue plate have large reservoirs to hold enough metal to be drawn in as the boolit freezes. Usually simple weighing of the boolit would reveal any hidden voids in it.

[geargnasher]

I also prefer large sprue holes, often enlarging them with a steel countersink bit and dressing the bottom of the plate flat again, they always seem to cast better that way unless the hole is large enough from the manufacturer.

Gear

[runfiverun]

Before I forget, casting metal too hot usually does nothing but create more shrink. Cast as cold as you can and keep the mold temp constant.

that pretty much sums it up right there.

for the long skinny ones i shoot straight and fast in the sprue hole.
the larger diameters i do better letting the alloy flow in from the side of the sprew hole.
boolit molds also benefit from vent lines throughout the entire cavity.

and anything over 400 grs usually benefits from pressure casting either with a ladle or the spout on the bottom pour.

[stubshaft]

I also prefer large sprue holes, often enlarging them with a steel countersink bit and dressing the bottom of the plate flat again, they always seem to cast better that way unless the hole is large enough from the manufacturer.

Gear

I'm with you there too Gear, I've modified a few of my sprue plates in much the same manner.

[leftiye]

A large sprue hole so the lead can stay liquid somewhere in the hole (as has been said). Hot mold so that the lead cools more slowly. Cooler melt temp as has been said (though 700 degrees seems to work best). Needs a mold heater to do this. Smaller stream not touching sprue hole (doesn't cool lead as it enters mold). Large sprue puddle to keep liquid metal available to cooling boolit.

[DLCTEX]

I have been of the opinion that cooling the sprue to speed cast can create voids. I used to cool sprue by blowing on it or even the wet sponge method, but find I cast better (more uniform in weight) boolits by letting the sprue stay molten longer.

[Chicken Thief]

Somewhere here is a thread (or more) about casting slugs for 4" cannons.
There's a lenghty discussion about avoiding voids in the cast projectile.

[williamwaco]

I am fascinated to hear someone talking about "shrink".

The generally held belief is that they actually expand after two to three weeks. I also hear a lot about "internal voids".

I do agree with your "suck in" statement. If the sprue puddle is small, you can actually see it being sucked in before it hardens. If there is not enough, it will leave a void in the base of the bullet.

It is not uncommon to drop bullets with voids in the center of the base. I have never seen a true internal void - as in - hole or bubble in the interior of the bullet. On several occasions when weighing a 150 grain bullet and finding one 5 or so grains under, I have taken that bullet to the grinding wheel and ground it to nothing looking for the void. I never found one.

As for dimensional shrinkage ( or expansion ) is simply does not happen. I have tested this three times with three different alloys and the results are always the same. After dropping from the mold, they shrink slightly until they cool off, then they are stable forever, in both length and diameter.

You can see the results of my most recent test measurements of 24 bullets here:

http://www.reloadingtips.com/pages/exp_110921a-cast-bullet-expand.htm

This test is currently at 149 days. I plan to continue it for six months.
I also have some of the same bullet cast 30 years ago this May that are exactly the same diameter as they were in May 1972.

[41 mag fan]

MFraser & gear....thanks for posting this info. I found it very useful and informative, as I'm sure someone else will too.

[MikeS]

WilliamWaco: You're thinking of something totally different than is being discussed. The OP is not talking about shrinkage after the boolit drops from the mould, he's talking about shrinkage while it's still in the mould, and going from liquid state to solid.

I forget where I saw it, but I remember reading an article where the author stated that most cast rifle boolits had a void in the very center of the boolit, and had pictures of several boolits that were cut with a hacksaw, and they all had a void in the very center of the boolit. The author went on to say that it's unavoidable, and that as long as the boolits all weighed the same that the void didn't matter. I believe he was talking about accuracy-wise, I don't know what an internal void that's centered in the boolit's diameter would do for a hunting boolit. I'm also not sure if I agree with the author that this void is unavoidable.

[geargnasher]

That's called "coring" and can be addressed with proper alloying.

Zamak was invented to address the coring issue when casting pure zinc.

Gear

[williamwaco]

WilliamWaco: You're thinking of something totally different than is being discussed. The OP is not talking about shrinkage after the boolit drops from the mould, he's talking about shrinkage while it's still in the mould, and going from liquid state to solid.

I forget where I saw it, but I remember reading an article where the author stated that most cast rifle boolits had a void in the very center of the boolit, and had pictures of several boolits that were cut with a hacksaw, and they all had a void in the very center of the boolit. The author went on to say that it's unavoidable, and that as long as the boolits all weighed the same that the void didn't matter. I believe he was talking about accuracy-wise, I don't know what an internal void that's centered in the boolit's diameter would do for a hunting boolit. I'm also not sure if I agree with the author that this void is unavoidable.


Mike, thanks for explaining that. The only casting I have ever done is bullets. I guess it is obvious that they must shrink away from the face of the mold or they wouldn't come out. ( Some times they almost don't come out anyway.)

As for the internal void, I don't know what was going on with the bullets cut with a hacksaw. I would like to try it. It would be a LOT less work than a grinding wheel. I used the grinding wheel because a 5 grain void would not be very large and I was afraid I might miss it using a hacksaw. Using the grinding wheel I saw literally every speck of the interior.

Were the bullets you saw cut lengthwise or crosswise?

I am retired and bored stiff. If it weren't for casting, loading, and shooting bullets, I would go crazy. I am always looking for something new to test.

As to effect on accuracy, I have always been told that the further from the centerline of the bullet a defect existed, the more effect it would have on the accuracy. Makes perfect sense but I have never tested it. I have played around with bullets with bumps, scrapes, and nicks on the point and always found them to hit right in the group with the others. Of course this is not formal testing and it was only at 50 to 100 yards.

What to do today? The shooting range is closed to rebuild the berm.

I have about 500, 170 grain Lee .30 Cal's and 300, 270 gr Lyman .375 Cal's in the shop. I wonder if I can find that hacksaw?


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[DLCTEX]

Williamwaco, grinding will not reveal the voids, unless huge, due to the lead being pulled and smeared by grinding causing the void to be bridged over. A hacksaw may avoid the smearing enough to reveal them.

[1bluehorse]

hmmmm, really??? I some how got the impression that using the "right techniques" and "proper incantations" that voids and little nastys could be eliminated to a degree as to not worry oneself about....now you say no... you're starting to make me think this bullet casting is just a waste of good metal. As in....not possible to make an accurate, stable, bullet.....So, whats next, swaging??????? [smilie=b:

[MikeS]

bluehorse: don't let all the technical talk about voids make you give up on casting. Many many stable accurate boolits were cast, and are still cast every day, often by folks that had no idea what a void is! If your cast boolits shoot the way you want them to, don't worry if they have voids in them, or other faults. There are people right here on this forum that cast great boolits, yet do everything wrong, there's even a person that never fluxes their pot! The number one most important thing for accuracy is practice. The more you shoot, the better you'll get. If casting your boolits lets you shoot more, so you get better, then they've done their job. Some people use cast boolits only to practice with, then use other bullets for their 'real' shooting, be it target shooting, hunting, etc. Then there are others that never shoot anything other than what they make themselves.

I'm in the second group, I make all my own boolits, and see no reason to buy any store bought bullets for any use, if I can't do it with my cast boolits, I don't do it.

[beagle]

It was probably me talking about internal voids. Back when we had the original cast site, my shooting partner was running experiments on moly impact coated smooth cast bullets as well as conventionally lubricated bullets in .30 and .32 that were impact moly coated before lubing.

As part of the coating process, he tumbled the bullets in jeweler's medium which is small pieces of scrap steel with moly added.

The moly coating worked fine but every, and I mean every bullet showed internal voids. Some at the base, and others scattered all over the bullet. These were randomly spaced and he found no method to eliminate them. He just recycled the worst cases and bullets with voids in what we considered critical areas.

With this culling process in place, he was still getting "minute of angle" groups in most cases despite the voids. This was with a .308 Win and also a .32-40 and the .308 Win was shot at what I consider higher than cast velocity loads out of a hand lapped Shilen barrel.

Voids we have to live with and they don't affect accuracy near as much as we think.

Any of you messing with the new small steel rod tumbling media might try tumbling a test lot of bullets for a couple of hours and see what emerges on your bullets. This is basically the same stuff just shaped differently and I'm anticipating that you'll see small sunken places all over your bullets.

Just like sausage. Enjoy the end product and don't look too closely at what went in and you'll be fine./beagle

[Cap'n Morgan]

This is a picture from FW Mann's excellent book 'The bullets flight from powder to target':

http://img834.imageshack.us/img834/9140/bulletvoids.jpg

The bullets are 7mm and 22 cal and as you can see they all have a shrinkage cavity in the nose. The 7mm has a piece of wire inserted in the cavities. Mann doesn't mention it but I guess the bullets were nose poured. Notice how the void in the 22 cal only show up because the noses have been split.

Mann's book is a great read. I believe you can find it at Google Books, but I can't find a link to it from here due some silly Danish copyright laws.

[williamwaco]

As for the internal void, I don't know what was going on with the bullets cut with a hacksaw. I would like to try it. It would be a LOT less work than a grinding wheel.

I am retired and bored stiff. If it weren't for casting, loading, and shooting bullets, I would go crazy. I am always looking for something new to test.

What to do today? The shooting range is closed to rebuild the berm.

I have about 500, 170 grain Lee .30 Cal's and 300, 270 gr Lyman .375 Cal's in the shop. I wonder if I can find that hacksaw?


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Well I sawed six of each into three disks. That is two cuts each on 12 rifle bullets.

I didn't find any internal voids. I didn't prove it can't happen but I did prove it doesn't always happen.


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[41 mag fan]

I am retired and bored stiff.
.


I would beg, borrow, lie, cheat, steal, pay and maybe kill to know that feeling!!
:bigsmyl2:

[williamwaco]

Williamwaco, grinding will not reveal the voids, unless huge, due to the lead being pulled and smeared by grinding causing the void to be bridged over. A hacksaw may avoid the smearing enough to reveal them.



Just finished some hacksawing. In my experience, it "Smeared" much worse than the grinding wheel. In fact I used some fine silicon carbide paper to grind off the smearing and saw marks so I could see any small small voids.

That said, after seeing the "Captain Morgan" photos. I am going to try splitting some lengthwise at the nose. More later.



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[williamwaco]

I would beg, borrow, lie, cheat, steal, pay and maybe kill to know that feeling!!
:bigsmyl2:


Mag!

Be careful what you wish for.

[williamwaco]

Those photos from the Mann book are a really long bullet.

I don't have a mold anywhere near that long. I don't know if that is a factor but I split three more Lyman .377s lengthwise with a hacksaw instead of a grinder and found nothing.

I may try some 170 gr .30 Cal's. they are about 1/8" longer than the bullets I have been dissecting. Then, maybe not. I am beginning to get bored with this game. Nothing is happening.

I realize I have not proven that it doesn't happen. But I have proven that it doesn't always happen.

PS, those dark spots are not voids. Under high magnification, they are revealed to be "sawdust" impressed into the face of the cut by the blade.


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[popper]

Lead and tin dendrite, tin is worse. Antimony and tin, when used with a refiner, make the structure more uniform and organized. This adds to strength we call BHN, when quenched properly, else you get non-homogenized with different versions of Pb/Sb/Sn or Pb/Sn/S.

[runfiverun]

i have broken open linotype pigs that have had huge voids in them.
with ww alloy you also have tin and arsenic and antimony that all help the alloy flow better hold together better and have smaller pores inside the cooling lead.

the alloy dr mann used was lead.
look at a lyman chart.
see that lead is the smallest boolit from the mold.
and as more tin/antimony is added, the larger the boolit is from the same mold.
i doubt you are getting "bigger round alloy" in the cavity.
i do think you actually get more [other than lead ] in the cavity it is an alloy and has internal molecular chains that hold it all together while in suspension. and so have less shrinkage.
thats the other thing that tin mixed in with ww's gives you besides a better mold fill out.
it allows you to cast cooler, and have a better internal bond holding the whole thing together better.

[KYCaster]

Those of you who have refined your alloy and casting technique to minimize voids in your boolits, would you please do a little experiment for me.

Take one of your best boolits with at least a .300 dia meplat, test the hardness at the center of the meplat then reverse the same boolit and test the hardness at the center of the base where the sprue cut is.

What did you find?

Just curious.
Jerry

[mfraser264]

So far, by culling as many have done over the years, I have some outstanding groups form the RCBS .30 165 and Lyman 311644.

Having maintained metal and mold temp, fluxing the alloy, titl angle of the lead stream and so on, there is always a few that are at a max weight. It tells me I have a lot to learn. My experience tells me that some boolits are very well poured and there is a sweet spot. I hve been recording metal temps to help from heat to heat.

Thinking about opening up the hole in the sprue which is mentioned many many years ago for the larger .30 calibers. At work we increase the pressure at the end of the casting cycle to literally squeeze the shrink out.

Anyway, it is an interesting hobby.

[mfraser264]

About cutting and looking for shrink, the size of defect we would be looking for would easily be smeared with the soft metal we are using, good try though. Weighing the boolit is still the best from what I have seen.

The trick is knowing the mold temp, metal temp and how lead solidifies. I use mainly Lino and it has 1 solidification temp that helps.

[williamwaco]

Those of you who have refined your alloy and casting technique to minimize voids in your boolits, would you please do a little experiment for me.

Take one of your best boolits with at least a .300 dia meplat, test the hardness at the center of the meplat then reverse the same boolit and test the hardness at the center of the base where the sprue cut is.

What did you find?

Just curious.
Jerry

I have done that many times with handgun bullets.

The story is that the readings are the same. - Sometimes.

The rest of the story is that the nose is harder than the base. - Sometimes.

And oh, yes. The end of the story is that the base is harder than the nose. - Sometimes.



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[KYCaster]

I have done that many times with handgun bullets.

The story is that the readings are the same. - Sometimes.

The rest of the story is that the nose is harder than the base. - Sometimes.

And oh, yes. The end of the story is that the base is harder than the nose. - Sometimes.



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Hmmmmm.........that's interesting.

Every time I've done that the base has been softer. EVERY time.

I concluded that the softer area is due to shrinkage and low density. I still believe that's true so what are you doing different than I'm doing to reduce the effect?

Jerry

[geargnasher]

Jerry, if I water-quench, the bases are harder usually. If I air-cool, they're usually the same.

Let me ask you a question: Do you cut your sprues by hand while still soft, or let them fully harden and whack them with a mallet?

Gear

[KYCaster]

Jerry, if I water-quench, the bases are harder usually. If I air-cool, they're usually the same.

Let me ask you a question: Do you cut your sprues by hand while still soft, or let them fully harden and whack them with a mallet?

Gear


I cut sprues by hand after boolit and sprue are both solid. I usually give it enough time to harden some so there is some resistance to the cut. As long as the boolit and sprue are solid, I don't see how the method used to cut the sprue would have any effect on shrink or density.

There's something else going on here and I'm having trouble wrapping my mind around it.

As Mfraser hinted at in his OP, it's extremely difficult, if not impossible, to eliminate the negative effects of shrinkage in a casting and some foundries go to extreme measures to reduce the effects to acceptable levels. I've examined x-rays of castings and bisected them (not the x-rays :wink:) for hardness and grain structure analysis....difference in density due to shrinkage is ALWAYS present.

Interesting subject....thanks for posting this Mfraser.

Jerry

[williamwaco]

Hmmmmm.........that's interesting.

Every time I've done that the base has been softer. EVERY time.

I concluded that the softer area is due to shrinkage and low density. I still believe that's true so what are you doing different than I'm doing to reduce the effect?

Jerry

Dunno.

I cast at about 650 - 700 degrees. I have never been able to control it closer than that. If I catch it above 700 degrees, I add some metal to cool it off. ( I never mix alloys. If I don't have another ingot, I add back sprue cuttings and culls.) If I have nothing to add back, I turn the fan on the pot and wait. ( and go get a diet Doctor Pepper. )

I use clip on wheel weights. Add a little range scrap if I want them softer or a little linotype if I want them harder. Sometimes I use straight range scrap - BNH 8 to 9.

Let the stream drop about half inch and impact the sprue plate so that about half the stream goes into the hole and about half hits the edge of the hole. Tilt the entire mold about 10 degrees to the right. Keep the metal flowing until the sprue puddle runs off the edge of the sprue plate. At that point it will be about 1/8" thick. This practice produces lots of sprue cuttings.

I always let the sprue harden until it will not deform if I whack it with the bottom of a teaspoon. This usually takes about 10 seconds. Then drop on a pad and air cool. This sounds like a very slow pace but it is fast enough I frequently need to stop and let the mold cool. I cool the mold by opening it, moving the sprue plate away from the top of the mold block and setting it in front of a fan for 30 to 45 seconds.

Now it's, your turn, What are you doing different?

I have always read "Never test on the base of the bullet. It is always softer than the nose." I just have not found that to be the case.

I am testing how bullet hardness varies with time. The latest version of that test includes. 408 separate BNH tests of a multitude of bullets. Every bullet was tested on the flat of both ends. ( They were SWCs ). The result was exactly as described before. There was no pattern. Sometimes the nose was harder, sometimes it was softer, and some times it was the same.

PS: All my testing has been done with handgun bullets. Mostly .44 caliber because there is more real estate and I can get more tests per bullet. These bullets measure exactly 0.75" in length. I wonder if a longer rifle bullet would produce a different result?

[DLCTEX]

My most uniform weight boolits come from casting at a consistent pace and with a generous sprue that is allowed to cool to a dull condition without cooling by blowing on it or using any other cooling method other than still air.

[geargnasher]

Jerry, it makes a difference as far as the rate of cooling goes. If you cut your sprue while the base is still mushy and expose it to cool air, it "quenches" faster and is thus harder if air-cooling the boolits. Pour rate and mould temperature have an effect on the temper of the nose.

Gear

[williamwaco]

Jerry, it makes a difference as far as the rate of cooling goes. If you cut your sprue while the base is still mushy and expose it to cool air, it "quenches" faster and is thus harder if air-cooling the boolits. Pour rate and mould temperature have an effect on the temper of the nose.

Gear


Gear, I have been experimenting with cutting the sprue while it is soft enough to operate the sprue cutter with my thumb.

I do not seem to grasp the method.

Using two cavity Lee mold 358-158-SWC
Alloy 75% wheel weights and 25% linotype.
Temperature 650 - 700

Fill from bottom pour.
Fill front cavity first.
Remove as soon as it is filled.
Wait about 2 seconds.
Push the sprue plate with thumb. at the first sign of frosting on the sprue - it opens easily.
The sprue on the front cavity is cut perfectly.
The sprue on the back cavity is too soft and tears out a sizable cavity from the base.

I know, simple, wait longer. The problem is that before the rear cavity is ready, the front sprue is so hard, I can no longer cut it "by hand".

This is a much faster pace than I am used to since I usually wait around ten seconds for the sprue to harden. Since the pace is so much faster I need to wait 15 to 20 seconds between fillings for the mold to cool. This pace produces bullets that are lightly frosted.

What would you recommend I adjust to find a pace that will work with "Thumb cutting".

[mpmarty]

I thumb cut all my 2 cavity molds after the first few casts. Six bangers are all LEE so all I do is move the lever. On first casts with the six cavity I only fill the first hole or two nearest the pivot point so the mold has time to heat up as I gradually add another hole in successive pours. I have broken off the sprue cutter handle once or twice.

[runfiverun]

my pot fills both cavity's at the same time.
but on my 4 cav's i alternate back to front,front to back, when filling the cavity's.
i use antisieze on my mold tops so a slight smear of lead is absolutely of no concern.
[another swipe with the q-tip takes it right off] usually the next opening is one count slower and it takes the smear off.
i am continously adjusting cadence and fill speed to keep the mold producing boolis that visually are identical.
coincidentally today i was checking and lubing the last batch of 311041's i recently done and found two with voids in the base.
i do recall using a damp rag to cool the mold once during the casting run [a practice i generally avoid] and i believe it was with these two boolits in the cavity's.
i was trying something new with this mold and did get it a bit hot.

[KYCaster]

Gear, I have been experimenting with cutting the sprue while it is soft enough to operate the sprue cutter with my thumb.

I do not seem to grasp the method.

Using two cavity Lee mold 358-158-SWC
Alloy 75% wheel weights and 25% linotype.
Temperature 650 - 700

Fill from bottom pour.
Fill front cavity first.
Remove as soon as it is filled.
Wait about 2 seconds.
Push the sprue plate with thumb. at the first sign of frosting on the sprue - it opens easily.
The sprue on the front cavity is cut perfectly.
The sprue on the back cavity is too soft and tears out a sizable cavity from the base.

I know, simple, wait longer. The problem is that before the rear cavity is ready, the front sprue is so hard, I can no longer cut it "by hand".

This is a much faster pace than I am used to since I usually wait around ten seconds for the sprue to harden. Since the pace is so much faster I need to wait 15 to 20 seconds between fillings for the mold to cool. This pace produces bullets that are lightly frosted.

What would you recommend I adjust to find a pace that will work with "Thumb cutting".


Fill the back cavity first. The cooler/harder sprue will be closer to the hinge pin = better leverage = easier cut.

Jerry

[KYCaster]

Jerry, it makes a difference as far as the rate of cooling goes. If you cut your sprue while the base is still mushy and expose it to cool air, it "quenches" faster and is thus harder if air-cooling the boolits. Pour rate and mould temperature have an effect on the temper of the nose.

Gear



OK, that explains how hardness can change from nose to base.

It also shows how variable hardness from nose to base can mask the presence of low density areas due to shrinkage.

It doesn't explain why my results are different than yours and William's.( but that's drifting away from the original subject)

It doesn't address the issue of shrinkage and density....how to avoid it or minimize it.....what effect it has on the boolit's flight....whether or not it really makes a difference.


Jerry

[williamwaco]

OK, that explains how hardness can change from nose to base.

It also shows how variable hardness from nose to base can mask the presence of low density areas due to shrinkage.

It doesn't explain why my results are different than yours and William's.( but that's drifting away from the original subject)

It doesn't address the issue of shrinkage and density....how to avoid it or minimize it.....what effect it has on the boolit's flight....whether or not it really makes a difference.


Jerry


Actually, I think maybe it might.
After reading this thread, It is obvious to me that my casting method leaves the bullets in the mold much longer than most others. Perhaps this makes my nose and base closer in hardness than bullets cut when the sprue is much hotter.

[williamwaco]

Fill the back cavity first. The cooler/harder sprue will be closer to the hinge pin = better leverage = easier cut.

Jerry


Duh! What a moron I am.

You are the MAN!

I am embarrased I didn't think of that.



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