32-40 weight variance issues.

[stubbicatt]

I casted up maybe close to 100 bullets yesterday, using a single cavity Saeco "Pope style" 200 grain, 32-40, bullet mould. I laid the bullets out in the order in which they were cast, and then began to weigh them.

Most weighed in the 203.5 to 203.9 grain range. The first one cast at 202.2 grains, number 10 at 203.5 grains. I guess this is to be expected as the mould comes up to temp and a rhythm is established. These would be culls in any event, no problem there.

I understand occasionally getting a light bullet -- indicative of a void perhaps in the casting. Occasionally, I would get a really heavy bullet, the heaviest was 204.5 grains. That I do not understand. Looks like I got 17 of them above 204 grains, and one at 204.5. When I see this, I begin to wonder if all those below 204.5 mightn't have voids?

If nothing I have learned, I have learned that once you get started, don't put sprues back in the pot, and don't stop to rest.

I have also learned that my technique needs improvement if I am seeing these sorts of weight ranges. I am casting at about 750-770*, ladle dipping. I have a RCBS dipper and a Lyman dipper, I find that the RCBS dipper is more user friendly, though I cannot say it is any more consistent.

In the pour, I skim the surface of the melt with the dipper to open up an unoxidized surface, and dip the melt from that spot. I pour a little into the pot thru the spout to make sure of unobstructed flow. Level the dipper, turn the mould 90 degrees, mate the sprue plate hole taper to the taper on the dipper, turn it all upright for a count of 3 seconds, and then disengage the ladle to pour a puddle on the sprueplate. Count 30 seconds, open sprue plate and put sprue in one box, the bullet in another, and line 'em up in the order they are cast.

I would like to get my finished product to .3 grains weight range. I am concerned that a significant percentage of the bullets weigh heavier than most, and reason that it isn't that the heavies had more melt in them for some reason, as the cavity is a finite volume, but worry that all the rest under that weight are imperfect for some reason, perhaps due to voids.

Total weight variation is 1.2 grains. Not good. Only thing I can reason is that the temperature was fluctuating, assuming a consistent technique, and I feel my technique was consistent.

Suggestions?

[Green Frog]

I'm going to guess that the "heavy" bullets are the normal ones and the lighter ones have voids of various amounts. The other possibility I would immediately recognize is that during casting the blocks are not being held together at a consistent rate, with slightly more loose hold giving a somewhat heavier bullet... it wouldn't take much to make the 1/2-1% weight difference you are observing. I've never been able to pour as consistently with a dipper as I do with bottom pour pots, but the technique you describe should not have that effect. Just some random thoughts.

Froggie

[runfiverun]

look at weight percentages in a relative term.
1 grain over 200 grs of total weight is 0.5%

[gwpercle]

Nothing wrong with ladle casting or your technique. You might try this, instead of a three second count to fill, one or two . Watch the sprue surface, when it frosts over , count to seven, then open the mould. This might help. Moulds each have their preferred techniques, how hot , how fast , cooling time , etc. It's just a matter of working with them until you find what they like.
What I do is keep the perfect ones, all filled out with perfect bases. The rest go back.
Then do not weigh them.....I did it a few times but it leads to insanity trying to figure out which ones to shoot, segregating them into different weights, it was just too much......Now if it looks good I shoot it.
Gary

[stubbicatt]

Thanks fellas. I have the data now. I suppose I can try the bottom pour feature and see how that goes. Try different techniques and compare.

I want to get the consistency to .3 grains if at all possible. Have you seen the 25 ring on the 200 yard German target? 1 ½ inches!

Regards,
Stubb

[Green Frog]

Thanks fellas. I have the data now. I suppose I can try the bottom pour feature and see how that goes. Try different techniques and compare.

I want to get the consistency to .3 grains if at all possible. Have you seen the 25 ring on the 200 yard German target? 1 ½ inches!

Regards,
Stubb

Been there, done that. I shot a Peregrine bench gun in 32/357 (Dell) built by Charlie Dell himself. My cast bullets never got me a 250 at Etna Green, but I shot some pretty impressive groups and was usually in the running at smaller matches. If you are within a half percent variance, I don't think bullets will be your problem. JMHO, of course.

Froggie
(yes, the same Green Frog as seen on the ASSRA board and sometimes writer for the SSR Journal)

[runfiverun]

you'll figure it out, I also weight sort the boolits that matter into either .1gr weight groups [223 at 2800+ fps in a 1-8 barrel]
and into .3 gr weight groups [30 cal 10 twist at 2400+ fps] they are also shot for accuracy and not just pure speed.
when you start spinning things fast, voids and anomalies start to manifest themselves a lot more than the pedestrian speed stuff does.

[stubbicatt]

Heh~! Green Frog! Glad to see you again.

I am surely not a hard holder. I think for me the introduction of a new rifle is most enjoyable as I learn the ancillary skills, bullet making, etc., that make it tick. I enjoy thinking it through and getting it to where the only performance variable is my own modest skill set.

Runfiverun, the velocities I am shooting at are closer to 1400 fps., and twist rate is a modest 1 in 15. I remember reading that some of the really good shots from 1905 or so were swaging their bullets to avoid voids and anomalies such as that from showing up on target. I haven't researched it any further, but I figure they must have been paper patched. I cannot imagine rolling a paper patched bullet for 223! Would need a jewelers loupe or the like to do that, and probably tweezers and the steady hands of a brain surgeon.

I think my next experiment is to see if a 20 count as opposed to a 30 count between sprue hardening and opening mould doesn't bring a little tighter weight spread. That and not introducing sprues to the melt until I take a break. Perhaps they introduce enough temperature variation to cause this issue. I may also lower the temperature of the melt 25* or so, as it skins over so fast at higher temperature. One variable at a time I suppose.

[John Boy]

Suggestions?
Stub, believe you have the drill down pretty good ... to tighten the variances up:
* Bring the pot temp and mold up to temperature so -
* With a 5 second ladle pour, the sprue puddle frosts in 5 seconds ... and keep a steady casting rhythm

Your Bell Curve variances will most likely open up larger if you cast the bullets with a bottom pour pot