Consistency applied.

[OS OK]

Thanks goodsteel...for the detailed information. It was informative, detailed and factual…mostly...well written and easy to read and follow. My first curve looked like the 'rolling hill country' in west Texas, now more resembles the 'Sierras' here where I live. You gave me a new tool and I appreciate it.

Charlie

[stu1ritter]

Tim, I only just found this thread, ran to the reloading bench and bell curved a random 100 of my last casting. Holy Cow. It is time to learn some consistency. I'd like to thank you and all the other posters for a most interesting and enlightening thread.
Stu

[Chris C]

Stu, I know what you mean. Really shocked me. I'd been using my "gram" scale to run bell curves because I didn't have an electronic grain scale............and didn't want to bother with using my balance beam scale to weigh all my boolits one at a time. Boy was I ever surprised when I took some "known" bullets that all weighed the same grams and put them on my new RCBS electronic grain scale. My bullets were all over the place. Guess I've a ton to learn about consistency!!! Just shows what one can learn sittin' in front of a computer monitor.

[stu1ritter]

This has indeed been eye opening. I took 100 of 150gr. WC from inventory and curved them, that's chart 1. This afternoon I applied Tim's technique of running 1 second of lead before filling the mold, no other change to my casting technique, lead temps, or anything, just the pre-run............photo 2. Photo 3 is the bullet stack for chart 2. I think this is going to be a great learning tool.
Stu

[popper]

Cast another batch of BO PB 145s, Al. 2x mould. I preheat on a hot plate but found dipping the SP in the melt gets it to good temp faster. I cut with gloved hand and found by feel that I get better boolits when it 'pops' when cutting. Too long and the base gets crooked, too early pulls divits from the base. Curious, I weighed with and without divits - difference is NOT from divits! My normal ES for visually good boolits is ~1gr. I calipered a few and believe now the difference is from cooled mould temp variation/dia. of boolits - alloy temp is PID controlled. Toward the end of the batch I tried letting the mould cool more (after sprue cut), they seemed to drop easier with only one handle tap vs 2 or 3. They all went in one pile so didn't check dia. variation. More testing later.

[popper]

Wife made jello last nite which got me thinking - I know, bad. Why does jello usually (and not often) get bubbles only on top? This is in reference to voids in cast boolits everyone so carefully weighs to find. Answer is obvious, it cools slowly and allows air bubbles to escape. Yes, I've seen pics of voids others have found - they can exist - and are about the size of #7 shot. Many suggest an alloy temp 100F above solidus temp but I feel it should be maybe 150F above to allow slower cooling.
edit:single 7 1/2 shot is 1.2gr. and 0.091 dia ERROR in calculations My hypothesis - you can't cull voids by weighing unless they are really large. You've visually rejected 'bad' ones, does that 0.0005 really make any difference in accuracy? I will NOT contest the idea of weighing to become a better caster.

[popper]

Read the 'spark-range' test of 223 yesterday, where they purposely create wobble and watch how long it takes to dampen due to aerodynamics of bullet. 100 yds! for a 'good' bullet design. Wobble creats the circular pattern on the target we see, due to cyclodal spiral path to target. Wonder if they have test data for the profile we shoot. I consider the 'void' of the previous post as LARGE for 30 cal, consider the 'shot' rotating around the CG with a 1/4" torque arm (creating wobble). Worst case would be that void on the outside near the base - I tested in 40SW and got IIRC a 5" ring of holes at 10 yds. Gyro stability formulas show SF is proportional to the SQUARE of difference in twist. Yup, twist does affect our unbalanced boolits. And base divits don't make much difference, gyro wise. Why this long trieste? IMHO it is the quality of the pour that determines the boolit quality. Like I mean WHEN IT COMES OUT OF THE SPOUT! Dribbles, crooked flow (crud in the spout), too fast or slow, DIRTY alloy. So far I haven't worried about frozen drips - nose defects have less effect than base - and the drips get remelted by the pour anyway. It's all about 'venting' the pour. Cast on.

[popper]

Correct an earlier error. 1.2gr shot 0.091" dia. Volume=0.00315 cu. ". Surface area 3.15" 30cal 0.6" long boolit (approx due to boolit real shape), Surface area = .729 sq. ". 0.001" dia. dif = 0.000729 cu. ", 0.004" dia. diff = 0.00292 cu. " volume. So, 0.004-5" dia difference is ~1gr. of lead. Confirm earlier hypothesis, weight difference is PRIMARILY due to dia. difference - which is due to casting tolerance (i.e. consistency). Now the real question. How does weight difference affect accuracy. Small variation in velocity? Doubt you could measure it. No change in stability factor. Difference in the amount of lube/boolit? Maybe. Difference in sizing due too bore - probably. Where does that in-compressible lead go? Into the lube grooves and base! Maybe boolit is now 'unbalanced'. Just some musings.
With consistent melt and mould temp the dia. variation should be minimum - therefore previous 'consistence' statements are valid. Boolits will be more consistent, is it worth the trouble? To become a better caster - yes. On the target? Maybe.