Weight variance...help

[sargeny1]

HI ALL.....What is an acceptable weight variance for handgun boolits....???? I am casting for 357...41 and 44 magnum....Have an ancient Lyman 429421 HP that NEVER varies more than 2 grains...a Ballisti-Cast #258 41 Mag. ...throws 223 to 225gr lyman #2 alloy...and a Mountain Molds ALUMINUM 357 160gr Keith ...throws 155 to 157gr..lyman #2 Alloy....BUT..with a LOT of rejects.....the rejects go 151 to 154grains....out of 200 boolits cast there will be 40 to 50 rejects....am about to give up on this mold....
WHO makes a 357 160gr mold..?????? Lyman 358429 is toooo long for most 357's....358477 is tooooo light in weight.....Am thinking of a SAECO #382.........

What say ye learned gentlemen..????
Thanks..
Pete

[sagacious]

The under-weight 'rejects' from your aluminum mold are very likely due to the mold not being hot enough. This is common. Get that mold hotter, and keep your pouring consistent, and the reject rate will fall to almost zero. It's not the mold's fault, it's the pourer's fault. Consistency in pouring technique = consistency in final product. Just pour-- don't sort rejects and fiddle with the mold during the pouring session.

A 160gr .358" mold is the same animal as a 158gr mold. Those two grains of lead count for nothing either way. There are lots of "158gr" molds out there to choose from that should work for you.

A few grains affects neither load safety nor hand-held revolver accuracy at reasonable ranges. Sorting handgun-caliber rejects that are two grains off is a huge expenditure of labor for vanishingly small gain.

For longer distance shooting, it will help-- as will other efforts at load uniformity. For more serious shooting at 100yds plus, keeping the cast bullet weight variance at not more than 2% works well. Sorting to a tighter weight-spread doesn't further tighten groups very much in my experience. Good luck.

[10mmShooter]

Sargeny,

Exceptable variance in bullet weight is really a function of your shooting skill and you ability to reload consistently(equipment, components etc). If you are capable of 1-2 inch groups at 25yards with "perfect ammo" 5% variance in bullet wgt will not make your groups any bigger. 5% is amost 8g variance for 150g bullet.

Although myself and I believe most people on the board will say a weight variance should be no more than the a few grains. Most of us will never be able to out shoot the bullets. I too fall into this trap, I always weight samples of my target rounds and like to stay +/- 2 grains....which for me at 25 yrs is simply not needed. I just cant help it. 2g variance on my 256g .44 K-SWC is less than .8% variance...... I'll never be able to out shoot the bullet.

If you shoot handgun calibers out to 50-100 yards, you might need to keep the variance to +/- 2% thats still 3g variance on a 150g bullet. But at that range, other factors will also come into play such as charge to charge variation, crimp tension, variations in seating depth, you will always be chasing perfection.

Just my .02 cents

[sargeny1]

Thanks guys for your help.....I can hold to a 2% weight variance with my 44 and 41 molds....I do not do ANY sorting of bullets while casting...I just keep pouring...I DO look at the bullets base as I cast...I keep the ones with perfect bases...a less than perfect base goes right back into the pot....I find that the hotter the lead and the hotter the mold, the better the bullets are....
Re my aluminum mold...jeez...beleive me, that mold is HOT when I cast....I can feel the heat from the mold thru the handles...!!!!! I am using Lyman #2 ALLOY and cast at 775 to 800deg....and I move fast to keep the molds HOT...pour...whack the sprue...perfect base..keeper....imperfect base goes right back into pot....the 44 and 41 molds NEVER vary more than 2 grains... SOOO...I'm good for hunting with these from 50 to 100 yds....?????
JEEZ...how fast do you have to cast with an aluminum mold....???????? Ya need 3-4 seconds for the sprue to solidify...then I whack it off and fill it again...etc...etc...etc.....

Thanks for your help guys...
Pete

[sagacious]

I am using Lyman #2 ALLOY and cast at 775 to 800deg....and I move fast to keep the molds HOT...pour...whack the sprue...perfect base..keeper....imperfect base goes right back into pot....

Thanks for your help guys...
Pete
That's your clue right there. With Lyman #2 at 775*F, variable base fill-out is likely to be either:
1) Mold not hot enough.
2) Sprue plate too tight to allow proper venting.

Other factors can be at work, but those two are the most likely. You should be getting perfect bullets with Lyman #2 at that temp. It's probably not the mold itself, it's the mold-management conditions or pouring technique. Mold temp is easy to address-- if the mold seems hot enough, but base fill-out is inconsistent, then the mold is simply not hot enough.

If inadequate venting is the culprit, try loosening the sprue plate screw by 1/8 to1/4 turn and see if the problem disappears. Best of luck.

[lwknight]

You should be able to get perfect boolits at 600 - 650 degrees with #2 alloy.
In fact when adding ingots my pot gets down to 580 ( temporarily) and I never slow down casting except
to let the molds cool.

When using higher tin content you can get the molds too hot and get shrunken band syndrome.

[sargeny1]

THANKS AGAIN, gentlemen.......I don't have a problem getting perfect bases on my bullets....the problem is weight variance with THAT aluminum mold......

AND...come to think of it....not all of the bands are completely filled out either....maybe I am running that #2 alloy too hot at 775-800deg...??? That leads to another problem...my lyman thermometer may not be working right...the dial is off the scale when cold.....WAY less than the 200 deg starting temp....is there a way to calibrate this thing..???????
THANK YOU ALL FOR YOUR HELP....!!!
Pete

[MtGun44]

Alloy freezing temp. Get some pure lead, melt and then record temp every 1 minute
until the alloy is solid. Plot and you will have a long flat portion of the time-temp plot
that shows the same temp for many minutes. This is the freezing temp.

Lead freezing temp should be available online somewhere. This is an invariant.

Bill

[shooting on a shoestring]

I had a simular problem with a 225415. Some bases were great, others not completely square cornered. Varying temperature didn't make a difference.

Solved by letting the sprue plate tab rest on the edge of the pot as I poured. This pulled the slack in the sprue plate up away from the top of the mould, letting it vent well for the pour. Perfect bases every time, cheap and easy, my favorite way.

[montana_charlie]

Alloy freezing temp. Get some pure lead, melt and then record temp every 1 minute
Lead freezing temp should be available online somewhere. This is an invariant.
http://www.theantimonyman.com/testingmetals.htm

[sagacious]

THANKS AGAIN, gentlemen.......I don't have a problem getting perfect bases on my bullets....the problem is weight variance with THAT aluminum mold......

AND...come to think of it....not all of the bands are completely filled out either....maybe I am running that #2 alloy too hot at 775-800deg...??? That leads to another problem...my lyman thermometer may not be working right...the dial is off the scale when cold.....WAY less than the 200 deg starting temp....is there a way to calibrate this thing..???????
THANK YOU ALL FOR YOUR HELP....!!!
Pete
Yes, 800*F is needlessly hot for Lyman #2. More heat is not always better. If reducing the temp increases the reject rate, then you almost surely have other problems to address. Usually, pourers turn up the temp when things aren't working right, but it does not generally address the actual problem.

Variable base fill-out, as you detailed previously, will cause weight variations of a few grains. There's not likely to be anything mysterious about that mold-- perfect fillout will give perfect results. The solution could be something as simple as fluxing before a pouring session. Keep working on it, good luck.