Author Topic: Cast bullet weight problem... (Read 1112 times)

IronKnees · « **on:** March 07, 2003, 02:34:00 AM »

Someone has posted the following question on one of my forums but is not getting much response... I know there is an answer to this, but for the life of me, I can't remember quite what it is. Can anyone here help. I'll have him jump over here and watch for replies.. Thanks all... Dave
STARTING WITH A 50LB MELT OF TYPE METAL THAT HAS BEEN MELTED AN FLUXED THEN POURED IN TO INGOTS.USEING A 10LB BOUTTOM POUR FURNACE OR MELTING POT.DOING EVERY THING THE SAME WAY. STILL GET 3 TO 5 GR VEARITION? CAN ANY ONE GIVE SOME HELPFULL HINTS. USING A 245GR KEITH STILE LYMAN. THANKS! PS OR DO YA SILL HAVE TO WEIGHT EACH ONE?

Lead pot · « **Reply #1 on:** March 07, 2003, 05:19:50 AM »

Hi IronKnees,

I will bite on this one,I can just tell you what I do that workes best for me to get uniform bullets.
When I make my ingots I make a large batch,like 90 lbs lead 3lbs tin.When the soup is soft enough to stir I flux it with canning wax a lot,It's sheep.You cant get the soup to hot ro the tin wont stay mixed try to keep it at about 750-775 I find that workes then make your ingots as fast as you can to keep it consistant.I have a lot of moulds so I can pour them almost at one time.I use muffin tins and regular ingot moulds.
Now when I cast I cast as close to 750-775 deg's that I can,my 20 lb Lee pot keeps the temp verry close A larger pot would be better.
the trick I find is the heet of the mould and the sprew plate you want to have a soft puddle on the plate for 3or 4 seconds at leadt so you dont get a void in the bullet base.If the soup is to cool on the sprew plate it will harden to fast and that creates a cavity in the bullet base even tough it looks good.
Another thing is dont get in a hurry to drop the bullet to soon.What will happen is you will pull the bullet out of round and pull the edges off the lube grooves.The secret is do it the same way all the time.And the proper casting temperature.I find the thickness of my sprew puddle is verry thin when I get consistant bulet weight.If the puddle is to thick the mould is to cold.
I cast most of my bullets with a ladle I get a more uniform and cleaner bullet.But i can also do it with a bottom pour pot but I feel it is not as good.
My pistol bullets I bottom pour.
A nother thing is use a good single cavity mould unless you seperate the bullets when they drop.
I found a good Lathe bore mould is the way to go,they cost more but they are sheaper in the long run.By the time you get a bunch of over the counter moulds looking for that super acurate bullet you can have several good custom moulds.My bullets run with in .2 gr.+ or - center.

Rright or wrong that is the way it workes for me IronKnees.Kurt

IronKnees · « **Reply #2 on:** March 07, 2003, 05:27:18 AM »

Thanks Lead Pot... If you will recall, you responded (I think it was you) to a post I did about casting 500 grain bullets for my .45-70, and how impressed I was with their consistant weight... They only varied a little... I'm sure this guy can get his "formula" fixed if he just finds out what mix to use...

Omaha Poke · « **Reply #3 on:** March 07, 2003, 10:08:44 AM »

Ironknees, I also am not the leading expert on this either, but there are several things that I think contribute to getting cast bullets with little if any variation in weight.

1. Get the mould hot and keep it a consistant temp.
2. Develope a consistant rhythm in casting. Do every step the same way each and every time you pour a bullet.
3. Make sure that you have an adequate sprue. As the melt cools in the mould, it tends to suck the melt down into the mould from the sprue excess. If there is not sufficient sprue poured, you with not get a good fill. I can tell when a bullet is not going to be a good one just by watching the sprue cool and seeing whether it ran out of metal to suck down into the mould.
4. Give the sprue time to change from a shiney to a satin look, and then wait 1 or 2 more seconds before cutting the sprue off. Check out the Paul Jones mould site for some good advice on opening and closing the mould.
5. Always cut the sprues off into a separate container, not back into the pot. Remelt them as necessary and flux at this time.
6. Make up your lead alloy in the largest batch possible. If necessary do 2 or more batches and then make a batch by mixing equal numbers of ingots from each batch into one batch of consistant alloy.
7. Mark your batches of alloy so you know for sure what you are making your bullets out of.

This works well for me, and I hope it helps your friend with his problems. I just poured 200 bullets for PPing and weighed them. I had 5 that did not meet my +/- .2 grains for this 430 grain bullet.

Omaha

Lloyd Smale · « **Reply #4 on:** March 07, 2003, 11:32:37 AM »

IVe shot alot of cast bullets out of handguns and a 3-5 grain variation in a 250 grain bullet will cause no adverse affect to the accuracy of any load out to 50 yards. I use to weight all my bullets and throw back the ones I thought were bad until my buddy who has shot 10 times as many as me watched me do this and laughed and told me hed take all the bad ones. He had dones accuaracy tests before and when I didnt believe him we did them together again using .44s .45s .475s and .500s and believe it or not sometimes the ugly rejects (not just a little weight difference but ugly bullets!) out shot the good ones. I now cast until the mold is hot and then keep everything. I shoot way to much to bother with weighting bullets.

BCB · « **Reply #5 on:** March 07, 2003, 12:41:21 PM »

IronKnees,

3-5 grains variations seems a bit much to me. I don't get that much variation using many large bore molds, and I really don't do anything special.

I am assuming it is a double cavity mold. When my molds get "up to casting temperature" and bullets are looking good, I fill the mold a dozen times and drop the bullets so I can segregate the front cavity from the back cavity. I then weigh and average each cavity. It just might be possible that one of the cavities is casting a bit heavy/light for the bullet design. It may not be anything to do with alloy or casting technique. Just a thought. Good-luck...BCB

Sky C. · « **Reply #6 on:** March 07, 2003, 01:23:40 PM »

I'll second the comment made by BCB-

3-5 grs. variation on a nominal 245gr. bullet seems extreme and his thought that it may be a variation between cavities also sounds correct and I suspect is the most likely cause assuming good casting technique.

The other item that could contribute is if there is contamination getting into the bullets from foreign material leaving voids or light spots. Even with the alloy itself is well fluxed and clean - there is a possiblity that the spout in the bottom pour furnace may be accumulating some crud that is finding it's way into the mould. If not already doing so - it may be beneficial to ensure that the spout is clear of accumulationso it doesn't find it's way into the mould.

FWIW-

Sky C.
Longmont, CO

Lead pot · « **Reply #7 on:** March 07, 2003, 03:35:31 PM »

Lloyd> I agree with you on the pistol bullets.I was heavy with the pistol matches.I shot a lot of bulls eye,and never paid attension on the weight for that 5-1/2" 9 ring or the 3-1/4" 10 ring at 25 yds.I think you could probably hit that with a spit ball.But that 32"x26" Ram out there at 547yds.is just a little different story .You need all of the advantages you can get.Or I do anyway HI.HI.Lp.

Lvl1trauma · « **Reply #8 on:** March 07, 2003, 04:57:07 PM »

5 Grain bullet variation- a LOT for a 250 gr. bullet- is only 2% variation. I don't routinely weigh my bullets or inspect them afterwards. I do what Loyd does. After the mould gets hot I keep pretty much everything unless it is something I know I screwed (ie- bad throw) up on or doesn't have a filled out base. I haven't noticed a difference yet at pistol ranges. I'll bet most everyone else hasn't either. Time is better spent burning powder than sitting around pondering over whether or not a bullet is exactly perfect.

Beau

Joe Kool · « **Reply #9 on:** March 08, 2003, 01:04:52 AM »

The problem may not be the alloy, it may be the mold. The mold may not be closing the same every time. Small bits of lead get between the blocks. The alignment holes in the one block can develop burrs around them and can cause the blocks to not close the same every time. A ding on the edge of a block came cause problems. Lee aluminum molds can warp if over heated, and not close the same each time. I carefully check the mold before every casting session. I also give the mold a quick check about every 100 bullets, while I'm casting. Open and close the mold and look into the bullet cavity while holding the mold up to the light, to see if there is a light gap. Make sure the blocks close completely each time. If not, there is something holding the blocks apart. Small bits of lead get between the blocks fairly often. I use a knife to carefully remove the lead bits. Use a set of micrometers and measure around the bullet, if the blocks are not closing properly the heavier bullets will be larger in diameter.
Try another mold and see if the weight variation problem still exists. If you cast too hot and the bullets drop frosty, the diameter will be smaller at the frosted areas. I've had 250 gr. bullets that varied 5 grs. when they were frosted a lot. About 85% of my bullets will be + or - a half a grain. The lighter bullets will have voids or drivings not filled out completly. The heavier bullets, will mike larger in diameter, telling me the mold didn't close compeletly.

BCB · « **Reply #10 on:** March 08, 2003, 05:54:51 AM »

Again, as I previously stated, I do believe that is too much variation among bullets. I doubt it would affect accuracy if they were shot from an open-sighted handgun, but I think they definately would affect accuracy if they were fired from a 'scoped handgun that is being shot from a good bench rest. Just my opinion...

My whole point was that a mold should not throw bullets with that much variation. That is why I suggested weighing the front and back cavity bullets seperately and see if the problem lies in the cavities. The person doing the casting may use "perfect" casting techniques and the variation may be in the mold itself (Joe Kool related to this also). Weighing the bullets would eliminate at least one variable.

I also have several molds for the 44 Magnum--429650, 44-250-K, and the 44-240-SWC and I guarantee they cast within several tenths of grains and not 3-5 grains variations...Period. Good-luck...BCB

Lloyd Smale · « **Reply #11 on:** March 08, 2003, 10:57:58 AM »

hell at 575 yards I might as well spit a ball at the target anyway :-D

Quote from: Lead pot

Lloyd> I agree with you on the pistol bullets.I was heavy with the pistol matches.I shot a lot of bulls eye,and never paid attension on the weight for that 5-1/2" 9 ring or the 3-1/4" 10 ring at 25 yds.I think you could probably hit that with a spit ball.But that 32"x26" Ram out there at 547yds.is just a little different story .You need all of the advantages you can get.Or I do anyway HI.HI.Lp.