.01 powder scales?

[Steve Blair]

Monte, [br]
I am running about one hour per one hundred cases, no seating. Depending upon the powder, my Chargemaster does a pretty good job of staying within bounds. The most tedious part for me is sizing cases. Everything else, SS pin tumbling, oven drying, trimming, etc., does not bother me as much as sizing. Getting three hundred cases ready for a tournament is just a PITA. I figure about 550 for Raton this year. If I take a full backup, that's 1100 rounds. I'll start around Fourth of July.

 

[BoydAllen]

Some time back, after looking at videos of the Prometheus, and a couple of other setups on Youtube, I put together a rig with my tuned 10-10 a SAECO measure, a web cam, and some odds and ends that allowed me to drop powder directly in the scale pan, with it on the scale, trickle the charge with my old RCBS trickler (which works just fine, thank you) and dump the result into a funnel sitting on a case. The scale was sitting at a right angle to the front of the desk (with the pan near the edge, and the camera was used to provide a magnified image of the balance pointer on my computer's LCD monitor. The tricky part was figuring out a way so that the powder did not bounce out of the pan. I managed it with a little Okie engineering. If I did my best my full cycle time worked out to about 20 seconds or a little less, counting dumping the powder in the funnel, and returning the pan to the scale. I think that a professionally tuned balance scale is sensitive enough for most any work related to reloading. I did mine, and have no doubt that Scott Parker would have done a better job, but even so, it is much improved.

 

[GrocMax]

Question-

#1
If you cut several granules of extruded powder every throw, thus changing the burn rate of those granules by changing their surface area, does tricking to a single granule really matter?

#2
If your case volume from case to case is off by an order of magnitude compared to the precisely trickled powder charge, what is the overall effect? Or do case volume variances not matter much to the overall volume of gasses behind the bullet when the powder is XX% completely burned?

 

[normmatzen]

By the time you are measuring to 0.01 or even 0.02 gn, you have to deal with air currents.
There is a good reason quality magnetic force balances have little "houses" over the pan as does even the GemPro 250.

I have recently changed from an Ohaus mechanical to the combination of a Lee dispenser due to its lack of cutting as many kernels and a GemPro 250.

To me this was the most accuracy for least money. The caveat is, you have to READ the DIRECTIONS! Even the GemPro has a hinged cover over the pan. Try calibrating it with and without the cover closed and you will notice the effect of wind currents!

 

[GrocMax]

You have a bunch of variables that contribute to the overall 'error band' (or circle), variables in the the machine- optics, the gun itself, the ammo itself, variables in the environment- wind, weather etc., variables in the shooter. Some of the variables you can measure and make more consistent, thus shrinking the overall error band somewhat, some of them you can't, so the error band will always be of a certain size over a certain time period. At some point, obsessing over measurements of one of the dozens of factors that contribute to the overall error band, no longer shrink the error. In the case of powder charge, I would imagine that the total charge weight % variance would be it, not what we are capable of measuring. In other words, a case that holds 30g of powder will not have the same critical charge weight variance in grains that say a 50BMG case holding 230g of powder, but I bet the percentage of error is the close to the same. So, if you can do a simple A-B-A test (try A, measure, try B, measure, go back to A, same as first A) changing ONE factor such as more precision in charge weight error and it does in fact shrink your error band significantly (halves vertical group size for instance) then its worth doing, if it doesn't its a waste of time, time to move on to another one of the factors contributing to the total error. What about energy loss into the barrel over a 5 or 10 shot string? Heat transfer in combustion is lost total energy, the percentage of heat lost is NOT the same first shot to last shot, can we measure and assign a grain value of powder charge to make up the difference and lower vertical further?

At some point its a time wasting obsession, not a critical factor at all, what is that point?