BruceB
09-15-2007, 03:14 PM
This is a spin-off from the interesting "Molds and Heat" thread, where every conceivable factor is being considered for its effects on the final product...the cast bullet. It gets very complicated, believe me.
Being a simple-minded soul, and having cultivated a "method" which gives me beaucoup boolits in very short order, I decided to post a few stats on two of my recent production runs.
ALL THE BULLETS IN THIS EXAMINATION WERE UN-INSPECTED.
On last Thursday, I cast about six hundred Lyman 311466 from a two-cavity mould. The Loverin designs like this one are considered a bit tougher to cast without flaws due to their multitude of small bands and grooves. Alloy was straight wheelweights, temperature was my RCBS-pot-maximum normal 870 degrees, and the production rate (measured over the last fifteen minutes of the session, when any fatigue after several hours' casting would be most evident), was 540 bullets per hour.
I measured ten of those 311466s a few minutes ago. ALL had basebands at .310", and ALL had the fattest part of their short noses at .302".
Weighing 61 of these 311466 bullets into half-grain batches (155.0-155.4, 155.5-155.9, and 156.0-156.5) I found 15 bullets in the 155.5-155.9 batch, 43 bullets in the 156.0-156.5 batch, and just three in the 156.5+ bunch. These three all showed the little "wires" created when the mould is filling so wonderfully-well that even the vent lines are taking some alloy...I love to see that. The wires, of course, were the cause of the slightly-heavier weight.
The second sample came from a June '07 casting run of 311291, one of our crew's all-time favorites. As you read the variations below, consider that these bullets came from a FOUR-CAVITY MOULD, repeat: FOUR different cavities. Measurements for both these and the 466s above were done with a Mitutoyo electronic caliper, good only to a half-thousandth, which is sufficient for my purposes.
311291 ten-bullet sample, nose diameters: all but two measured .301", and the other two were at .3005".
311291 ten-bullet sample, baseband diameters: seven measured .312" and three were .311".
Grabbing a big handful of bullets from the bin, I came up with exactly 85. The weight classes were established as 175.5-175.9, 176.0-176.4, and 176.5-176.9.
40 bullets fell into the 175.5-175.9 range, 35 bullets into the 176.0-176.4 range, and ten into 176.5-176.9 class. Again, the ten heaviest showed the 'wires". I can state that the vast majority of the two larger groups will fall into a half-grain spread from 175.7 to 176.3 grains.
So...casting hot at 870 degrees, casting fast at over 500 per hour with the 2-cav and probably at least 800 per hour with the four-cavity, with NO FLUXING, adding metal to the pot frequently without stopping the casting, water-cooling the sprue and plate, I still come up with extremely small dimensional and weight variations. For my purposes, and for those of most of us here, I believe, maximum weight spreads of one grain and diameter spreads under a thousandth are amply good.
This is not to be interpreted as throwing rocks at the more-scientific among us! I post this so that perhaps a newcomer won't be so overwhelmed with the complexities being discussed, that he becomes discouraged without ever trying this hobby. Plus, of course, I don't mind bragging JUST a teensy little bit....
Being a simple-minded soul, and having cultivated a "method" which gives me beaucoup boolits in very short order, I decided to post a few stats on two of my recent production runs.
ALL THE BULLETS IN THIS EXAMINATION WERE UN-INSPECTED.
On last Thursday, I cast about six hundred Lyman 311466 from a two-cavity mould. The Loverin designs like this one are considered a bit tougher to cast without flaws due to their multitude of small bands and grooves. Alloy was straight wheelweights, temperature was my RCBS-pot-maximum normal 870 degrees, and the production rate (measured over the last fifteen minutes of the session, when any fatigue after several hours' casting would be most evident), was 540 bullets per hour.
I measured ten of those 311466s a few minutes ago. ALL had basebands at .310", and ALL had the fattest part of their short noses at .302".
Weighing 61 of these 311466 bullets into half-grain batches (155.0-155.4, 155.5-155.9, and 156.0-156.5) I found 15 bullets in the 155.5-155.9 batch, 43 bullets in the 156.0-156.5 batch, and just three in the 156.5+ bunch. These three all showed the little "wires" created when the mould is filling so wonderfully-well that even the vent lines are taking some alloy...I love to see that. The wires, of course, were the cause of the slightly-heavier weight.
The second sample came from a June '07 casting run of 311291, one of our crew's all-time favorites. As you read the variations below, consider that these bullets came from a FOUR-CAVITY MOULD, repeat: FOUR different cavities. Measurements for both these and the 466s above were done with a Mitutoyo electronic caliper, good only to a half-thousandth, which is sufficient for my purposes.
311291 ten-bullet sample, nose diameters: all but two measured .301", and the other two were at .3005".
311291 ten-bullet sample, baseband diameters: seven measured .312" and three were .311".
Grabbing a big handful of bullets from the bin, I came up with exactly 85. The weight classes were established as 175.5-175.9, 176.0-176.4, and 176.5-176.9.
40 bullets fell into the 175.5-175.9 range, 35 bullets into the 176.0-176.4 range, and ten into 176.5-176.9 class. Again, the ten heaviest showed the 'wires". I can state that the vast majority of the two larger groups will fall into a half-grain spread from 175.7 to 176.3 grains.
So...casting hot at 870 degrees, casting fast at over 500 per hour with the 2-cav and probably at least 800 per hour with the four-cavity, with NO FLUXING, adding metal to the pot frequently without stopping the casting, water-cooling the sprue and plate, I still come up with extremely small dimensional and weight variations. For my purposes, and for those of most of us here, I believe, maximum weight spreads of one grain and diameter spreads under a thousandth are amply good.
This is not to be interpreted as throwing rocks at the more-scientific among us! I post this so that perhaps a newcomer won't be so overwhelmed with the complexities being discussed, that he becomes discouraged without ever trying this hobby. Plus, of course, I don't mind bragging JUST a teensy little bit....