Varying bullet weights with Lee C309-170

Hi all!

Tonight I cast some Lee C309-170 COWW for 30-30 and I observed something odd while doing some quality control..

I cast 177 total bullets, tossed 18 for defects or out of weight tolerance so I ended up with 56 bullets that were within .5gr of 177.1 grains and 103 bullets that were within .5gr of 176.8 grains.

The two sets of good bullets looked really nice and were mostly within .2 or .3 tenths of each other but I thought it was very odd that the two different weights were so far apart and could only surmise that the Lee 2 cavity mold was throwing two different bullets weights but I also find it odd that the number of 176.8 gr bullets outnumbered the 177.1 grain bullets by almost double.
It's been a couple of years since I cast and even then I don't have much experience casting, I kept the lead in the Lee 20# pot between 750-780° and the castings looked nice I thought.

Would that be the mold throwing two different weights you think? I just think it's odd that even then one set outnumbers the other set by almost double.

It's hard to say exactly. It could be something as simple as one cavity being hotter than the other, if you were always pouring one first. Unless you were getting a few for hunting, you can lump all of them together, no need to sort, those are very good numbers.

One cavity being hotter than the other does make sense, my routine is to fill the back cavity first and then fill the front cavity so next time I'll rotate the two cavities and see if that changes anything. Yes I am going to use some for hunting so I'll make sure all of the hunting bullets are as close to the same and mix the rest ... thanks megasupermagnum.

How are you casting them? I made these last year when I was starting casting https://uploads.tapatalk-cdn.com/202...0b4ff0fbd8.jpgpressure casting with a ladle. They weigh between 164 and 165.5 grains, I think the difference is because I was impatient, the lead was not fully solidified, and some of the bases have holes torn in them. They still shot ok without gas checks, within the bounds of six cups of coffee and operator error.

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Your weight tolerance for the bullets is fantastic by the way in my opinion.

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What is COWW? I remember that WW means wheel weights but I forgot what the CO stands for. It's been a while since I've been back on this site. I haven't cast any boolits for a few years. I still have about 100 lbs. of lead in ingots and need to get back to reloading. I've been trying to find some 4895 to reload my .30-06. I've cast enough last casting to reload about 1000 rounds. Have 660 cases cleaned, primed and expanded mouths ready for reloading. Just need the powder. On a fixed income since retiring, so $$ comes very hard these days. Bullet Caster

COWW= Clip on wheel weights

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I find the same kind of thing with my 2 cavity mold from Accurate. I just segregate the two different weight groups. Yes, I do find when shooting I get smaller groups that way. This has been a consistent thing with me, enough that I have plotted out bullet weights from a casting session and there are two distinct bell curves with the peaks separated by a few tenths of a grain.

FWIW, when I shoot the two different weight groups there is very little change in POI, maybe 1/4" to 1/2" at 100yd. Not very important if hunting, but, it is enough to change a target score from 10's to 9's.

I also tracked the weights of bullets from my 4 cavity mold (different bullet and NOE mold). I think the overlap of bell curves was enough that instead of seeing 4 different peaks I just had a slightly wider bell curve. I still separate into different weight groups for loading and shooting.

For a comparison I weight checked some jacketed bullets. Berger 155gn BTHP had a spread of 0.3gn and Hornady 155 ELD match bullets had a spread of 0.5gn. They both shoot near 0.5MOA for me with the Berger's being much more consistent.

PS the 'bell' curves I refer to above are really not bell curves as the upper end has a much sharper drop off than the lower end. Also to be expected since most bullets from either cavity will tend to have fewer and smaller inclusions.

358429 I cast using a Lee Pro 4 20# pot and poured directly into the mold, I do have a lead thermometer and try to maintain a temperature between 750-780° and drop them into water. Your bullets look really nice, I don't see anything wrong there! Is that using the Lee C309-170 Mold?

Charlie b ... that's interesting, that's probably what is happening with me. In the past I really never paid that much attention, weighed a few and loaded them all but really never saw a whole lot of spread in groups but from now on I'll weigh each bullet and seperate the groups just as you said.

I've wondered if the sprue, mounted closer to the one cavity, serves as a heat sink and can contribute to this variance. I've really seen it happen on 5 and 6 cavity molds

RickF yes that is the 170rf 30 cal lee mold. My introduction to hand load 308 Winchester[emoji3] . I was powder coating/sizing 311/loading them in 308 winchester with out gaschecks with starting loads of 4227 and 3031 powders from lyman4.

The shooting range has an electric motor for the paper targets. A fun game is to program a timer and the targets will turn 90° on edge, then turn to face you. Then turn, etc.

I burnt threw this entire boxhttps://uploads.tapatalk-cdn.com/202...302119f58f.jpg doing that rapid fire shooting, I had so much fun. Shooting the browning blr 308 at fifty yards in three seconds I can bring the gun up, shoulder it, find the sights, fire, cycle the lever, and if my focus is good hit something the size of an apple every time.

Are you shooting those through 336 Marlin?




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Quote:

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Originally Posted by 358429

Your weight tolerance for the bullets is fantastic by the way in my opinion.

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Exactly what I was thinking. "Within 0.5gr of of 176.8 vs 177.1" A 1.3gr spread on them all (+/- 0.65gr of 176.95gr? That's a 0.3% variance from the mean. I'd be pretty happy with that!

Quote:

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Originally Posted by 358429

Your weight tolerance for the bullets is fantastic by the way in my opinion.

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Exactly what I was thinking. "Within 0.5gr of of 176.8 vs 177.1" A 1.3gr spread on them all (+/- 0.65gr of 176.95gr? That's a 0.3% variance from the median. I'd be pretty happy with that!

Recharge the pot with more lead with lead in the pot and the bullet weights will change or
Empty the pot and recharge with a fresh batch of lead, the bullet weights will be different than the first batch

im not a precision shooter and dont weigh all my bullets, but just for fun this summer I cast with mp mold 454360 , 4 cavity mold, with each cavity having a different hollow point pin and one with the flat to make solids, bullet weights varied from about 255 grains to 270 grains. I loaded them all with 19 grains of 4227 powder.
I didn't shoot into a paper target using a rifle rest at a sit down bench. I just stood up and pointed the rossi 92, 45 colt at a tree and shot. they all seemed pretty good and accurate.

I think you are using a comparison of Apple's to Oranges. If I were shooting competition I would like my boolits to be with in 1/2 grain plus or minus. For hunting your weights are fantastic. If you can shoot 3" groups at a 100.yds. with those boolits all mixed up you won't have any problems. I would use Gas Checks though.

That is actually quite good 7 I wouldn't get worried until I was 2-3gr diff in bullets meant for 50y & beyond accuracy.

Many variables cause differing weights ... double cavity mould being most obvious... Lee moulds are not the most consistent ... and you have one cavity cooler than the other ...the cavity fartherest away will always be cooler . Try filling it first every time and the cavity closest to you fill last .
Be consistent in sprue cooling time .
Other than that ... not much you can do .
BPC Match shooters get a single cavity mould and cast all their competition boolits with it ...
Might want to invest in a better mould like NOE or one of the other custom makers .
I can tell you that NOE aluminum blocks are at least 3 or 4 times the size of the new Lee blocks ...
I think Lee has made a mistake in making their blocks so small ...they loose heat way too fast .
Or do what I do ... Visual inspection - perfect base and no wrinkles and all sharp corners ...
it gets shot . All else, back in pot .
Do Not Weigh Them .
Gary