Acceptable roundness from a good mold

[philthephlier]

What is acceptable roundness in thousandths from a good mold?

[Calamity Jake]

.002-.003 does not bother me one bit!!! The size die or barrel will make it round

[dubber123]

I really like to see .001 or less. Much more than that, and I can see it in the bands when sized, which bugs the crap outta me. Thats probably all it does, but.....

[Humbo]

Also depends if the smaller portion of the bullet is undersize, if it's not then a couple of thousandths is fully acceptable.

[mrbill2]

If the jacketed bullet companies tried to sell us bullets that are out of round .003 or .004. we would sue.

[jbunny]

it's common to beagle a mould for an oversized bore and once sized shoot
ok,
jb

[lead Foot]

I really like to see .001 or less. Much more than that, and I can see it in the bands when sized, which bugs the crap outta me. Thats probably all it does, but.....

Me too ~ we must be twins. But that said I bought a new RCBS 7mm-145- SILL mould ~ it was more than .004 outta round, I was so disappointed. In the States you have great service but here in Australia they don't wanna know ya after you bought it. Anyway you gotta try it and see how it goes. Well I nearly fell of my chair ~ the first three shots went in the same hole @ 100 meters. But I have to use a softer lead mix to fit in the throat.
Lead foot;

[Bret4207]

As close to perfectly round is preferred. But .002 and smidge more is workable as long as the boolit is fat enough to start with.

[qajaq59]

Sorry folks, but it seems to me if I pay for a mold to be round then it should be. They don't advertise a mold that's "almost made correctly" so why sell them that way? But that's just me and I'm always in the minority on what is acceptable work.

[pdawg_shooter]

I dont worry about it. You kick that out of round bullet in the butt with 30,000+psi and force it down a round barrel I would bet it is about as round as it can be.

[armyrat1970]

That's one reason I size my boolits with my Lee sizers. To get them round. I do it in two steps. I notice how I am placing the boolit in my sizer. Push it through. Place it in my sizer again with 1/4 turn and size again. Checking the boolit all around they are the same and very round. I have checked factory boolits that are not quite round so it may not be such a big deal but I want mine as close as possible. Sure it's 'gonna size through your bore but will it be off centered or off balanced? I would rather have them as round as possible before pushing them through the bore.

[BABore]

On a very good day, I can cherry cut a mold that will drop a boolit that is only 0.0005" out of round. After machine cutting, I hand deburr and clean the mold, then hand cut it again with the cherry. Measuring the cavities as best I can, they are round. Then, lo and behold, I cast with another design and I'm over 0.001" out of round. What gives?? Sometimes, because of boolit design, cavity volumes versus block size, alloy, alloy temperature, or block temperature, a mold will not grow evenly with the heat. I've commonly had mold drop boolits that were both big and small at the parting line just by changing alloys or temperatures. A round hole will grow evenly when heated. Spilt it in half and things change.

[257 Shooter]

BABore, Thanks for that explaination. It clears up some things I have been wondering about.

[Will]

I had a Lyman 311410 that dropped boolits .305X.311 I could never get better than a 12" group with them. After trying many things I sent Lyman an e-mail and, even though by this time it was well out of the warranty period, they had me return it for a new one.

[Lead pot]

A good mould will not cast a bullet that .001 out of round.
A bullet .002-003 our of round will be out of balance even if you drag it through a size die and push the excess in the lube grooves.
Just think at what RPM that bullet is spinning. It will make it to the iron the Cowboys shoot but they will plow dirt at long range.
Take a .358 diameter .357 mag bullet fired from a rifle at 1200 fps with say a 1/19 twist that bullet is spinning at about 96,000 rpm. Man wouldn't that shake the dishes out of the cabinet:grin:

[Lead pot]

I might add this.

A good mould that is cut on a CNC will drop a bullet out of round if you get in a hurry and open the block before it is set.
A bullet is not hardened enough if you see the sprue puddle sets then open the block right at that point the alloy in the cavity is still like butter and it will pull it out of round, if you dont pull it it will change as it hits the towel when it falls out of the mould.

[felix]

Keep in mind, though, that if the boolit is out of round equally at 180 degrees, the barrel will/should make it absolutely round, assuming an even number of lands. ... felix

[Bret4207]

A good mould will not cast a bullet that .001 out of round.
A bullet .002-003 our of round will be out of balance even if you drag it through a size die and push the excess in the lube grooves.
Just think at what RPM that bullet is spinning. It will make it to the iron the Cowboys shoot but they will plow dirt at long range.
Take a .358 diameter .357 mag bullet fired from a rifle at 1200 fps with say a 1/19 twist that bullet is spinning at about 96,000 rpm. Man wouldn't that shake the dishes out of the cabinet:grin:

I have a lot of "good" moulds that cast slightly out of round and a few "good" moulds that cast well over "slightly" out of round. You can cut the hole as round as you want, but the heat and shape of the mould allow that beuatimus perfectly round hole to become oblong no matter what you do to one extent of another. Some molds do it more than others, but with the proper equipment to measure things I find it's still a crap shoot. I also think the amount of distortion varies with mould temp.

[Lead pot]

Keep in mind, though, that if the boolit is out of round equally at 180 degrees, the barrel will/should make it absolutely round, assuming an even number of lands. ... felix

I agree with that. what I'm saying is if the bullet is out of round it dont matter what you push it through especially a GG bullet the lead will get pushed into the grooves and it will still be out of balance.
You cant compress lead but you can make it flow.


Yes Brett bullet alloy will shrink some as it cools.
A good way to check a mould is to cast a bullet with cerrosafe.

[felix]

It is difficult to cast boolits without air holes. So, hopefully the holes are equally distributed, and the lands will push in the lead enough and if not in, then out uniformly. Barrels with even number of lands have a better chance in getting the boolit correctly balanced when the boolits are not. Perfect boolits have a chance to shoot better in an odd number of lands, given the same number of them (except by one, of course). More lands, more balance probability with bad boolits. ... felix

[StarMetal]

A good mould will not cast a bullet that .001 out of round.
A bullet .002-003 our of round will be out of balance even if you drag it through a size die and push the excess in the lube grooves.
Just think at what RPM that bullet is spinning. It will make it to the iron the Cowboys shoot but they will plow dirt at long range.
Take a .358 diameter .357 mag bullet fired from a rifle at 1200 fps with say a 1/19 twist that bullet is spinning at about 96,000 rpm. Man wouldn't that shake the dishes out of the cabinet:grin:

Lead Pot, that bullet fired at 1200 fps out of a 1/19 twist is only doing 45473.684 rpm.

1200x720
19 = 45473.684

Joe

[Trifocals]

I don't worry if a boolit drops from a mold out of round, unless it's in excess of .002" out of round. If the minor dimension of an out of round boolit is larger than the sizing die, the die will make the bullet round. Also, if the minor dimension of an out of round cast boolit is larger than a barrel's groove diameter, the boolit will be swaged to round as it travels down the barrel. It's nice to strive for perfection as we make our cast boolits, but perfection is nearly impossible to achieve. There are just too many gremlins in the casting/sizing process for perfection. Go with what you have. Make it as good as you can and the end result should be acceptable for most purposes.

[Lead pot]

Lead Pot, that bullet fired at 1200 fps out of a 1/19 twist is only doing 45473.684 rpm.

1200x720
19 = 45473.684

Joe

Well that still is fast enough to make you dizzy:veryconfu

[Bret4207]

You can have as round a boolit as you want. It still won't matter if the boolit is seated cockeyed, if the chamber is cut off center, if the boolit hit's the feed ramp and is forced cockeyed or if the loaded round sits in the chamber out of line with the bore. There are a mess of variables, and then you have obturation to deal with (whether you plan for it or not) and the resulting damage than can happen. All you can do is load as perfect a round as you can and minimize the variables.

While I appreciate a round boolit and perfectly loaded cartridges, there are so many variables involved I sometimes stand in awe that we're able to do what we do so successfully.

[armyrat1970]

You can have as round a boolit as you want. It still won't matter if the boolit is seated cockeyed, if the chamber is cut off center, if the boolit hit's the feed ramp and is forced cockeyed or if the loaded round sits in the chamber out of line with the bore. There are a mess of variables, and then you have obturation to deal with (whether you plan for it or not) and the resulting damage than can happen. All you can do is load as perfect a round as you can and minimize the variables.

While I appreciate a round boolit and perfectly loaded cartridges, there are so many variables involved I sometimes stand in awe that we're able to do what we do so successfully.

Great post and very well put. I need say anything else.

[243winxb]

If your tumble lubing, i would worry about it. Just measured. Got .0013" and .0016" taking 4 measurements per bullet X 3. Two different alloys. Mould is a Saeco 158gr swc. I remember also measuring a Lyman 45acp bullet 2 places on the bullet, the center and on the split. The difference was .4520" and .4515" as i wanted to test tumble lubing.

[35remington]

I find the most common condition to be out of roundness in relation to the mould part line, but it can vary.

If the out of roundness is 90 degrees to the part line, with it being fatter at ninety degrees and skinnier at the part line, I don't worry about it too much, as the bullet is still balanced. I may look for means to close the mould a little more tightly, and look at locating pin alignment, but oftentimes these bullets shoot fine because they're not out of balance.

Just repeating what Felix asserted - that out of roundness does not mean out of balance every time, as some assume. I have several out of round moulds that shoot marvelously.

Shoot the bullet first. Then decide if the out of roundness matters. Many times, it won't.

[mrbill2]

Round bullets can have internal voids. To say that round bullets are balanced and out of round bullets are not balanced would not seem to be a 100% true statement.

[lathesmith]

Have any of you guys that are wringing your hands over these small amounts of out-of-roundness ever done any firing tests to show that a small amount of out-of-roundness can be directly responsible for larger groups? And if so, how much larger?

Or, have you ever loaded some rounds in some nice, thick brass, then pulled the bullets, to demonstrate that your perfectly round lead slugs stay that way even after the stresses of actually being loaded?

lathesmith

[jsizemore]

To say that round bullets are balanced and out of round bullets are not balanced would not seem to be a 100% true statement.

I agree with mrbill. You can assume that the out of round is all on one side. Not necessarily, and probably, not likely.

[45-70 Chevroner]

I have read several articals about shooting bullets that are obvieously not balanced just from looking at the pictures of them, for instance one bullet had its nose pushed to the side buy at least 1/6 in. these bullets were jacketed SP. and they still shot to point of aim. I don't think out of round has much more effect than bent bullets. The biggest worry I would have with out of round bullets would be if they are not at least round enough to touch the sizing die all the way round during the sizing and lubing process, and I have had moulds that were that much out of round and I got rid of them. The steering end of the bullet and the consistant weight are much more important. P.S. I don,t shoot bent bullets because they are ugly, and I think most of my bullets are a little out of round at least .002. I shoot some pretty nice groups with those bullets. I know there are quite a few of you out there in my age group, and like most in that group I shoot to satisfy myself. A couple of (.002) is not going to spoil my fun. If I don.t shoot a real good score every time it means I,m only human

[crabo]

[QUOTE=35remington;686947]

If the out of roundness is 90 degrees to the part line, with it being fatter at ninety degrees and skinnier at the part line, I don't worry about it too much, as the bullet is still balanced. I may look for means to close the mould a little more tightly, and look at locating pin alignment, but oftentimes these bullets shoot fine because they're not out of balance.

QUOTE]

I was casting with an LBT mold and the blocks needed a little help closing each time. This got annoying so I put a little Bullplate on the handle were it was attached to the mold blocks. What a difference it made. The mold blocks started closing perfectly and the boolits rate when way up.

I am going to start doing this on all my molds when I cast.

[qajaq59]

Actually I think Bret hit the nail on the head. With all the imperfections in our rifles, cases, primers, powder, cast bullet, to say nothing of how well we shoot, it's a bloody miracle that we can hit anything at all. Everything we use, to some degree, has a flaw. So cast and shoot them and have a ball.

[mrbill2]

When I found this bullet I just noticed a very small pin hole. I took a pencil and probed around the pin hole and look what I found. Quite a sizable hole. I could have just a well missed the little bugger and then wondered why my group opened up. I weigh all my rifle bullet to try and cull bullets like that one. Out of balance for sure.