Digital Scale variation

[Mastiff54]

After reloading some 223 rounds my brother and I decided to sort the assembled cartridges by weight,approx 184gr)

We started off with a Lyman DPS 1200 and when I rechecked some of the cartridges the readings were different by up to .4 grains than what the cartridge checked a few minutes earlier.

Thinking it was the scale I got my RCBS Rangemaster and sorted them again, similar results !!

We tried it zeroing on a cartridge then sorting by weight difference and by zeroing the scale and separating by actual weight.

We compared between scales and found they often differed by .2 and once in a while .3 grains

My brothers reloading room is draft free with a very solid and level bench. I have lost all confidence in these scales for anything closer that .4 grs.
Is there a solution or better scale than the Lyman and RCBS??

 

[BillK]

Yeah a mettler lab balance!!! I use the college model!!!

 

[ronemus]

My scale,a Pact Digital Precision) is sensitive to electrical noise on the power line - it would fail to calibrate if my furnace blower was running. A good filtered power strip by TrippLite solved the problem. The second/third generation scales have an auto-zero feature,a weight of +/-0.4 gr is reset to zero), so zero drift isn't as much as a problem; however, I always warm up the scale for at least 4 hours before using it. If I know I'll be using it the next day, I'll just leave it on overnight.

 

[CAT977]

I have had no problems with my Lyman 1200, thought I did but it was the bullets,Barnes 62gn vg) big variation

 

[Mastiff54]

After contacting Lyman, RCBS and Ohaus I have gathered the following information:
Most of these scales use strain gauge technology. . Learn more on strain gauges at http://www.sensorland.com/HowPage002.html

The strain gauge can give you good weighing results for weighing static loads, but can drift much more due to temperature variations which may occur by just by using the scale. Especially those with the feed motor,like the DPS 1200) which will generate heat just from being used. Zero often, and calibrate when suggested by the system. Any voltage fluctuation may confuse the electronics into thinking the load has changed.

These scales are VERY sensitive and will detect any movement which could cause the strain gauge to flex at all under it’s load,including the empty pan). Light drafts can be caused by the movement of your hand while loading the scale and will affect the reading, but should stabilize once the 'breeze' subsides. Test it – it’s cool!

Any vibration of the scale will affect the reading if it causes the scale to move at all. Another fun test.

AC Line noise will affect the scales, a line conditioner is an excellent investment.
Fluorescent lights are not a problem unless they are close to the scale, in the 2 to 3' area.
Cell phones can cause interference with electronics, all recommend that they be turned off if near the scale,10ft)

Both RCBS and Lyman have offered to evaluate the scales for me, I pay shipping, which I will do, and am grateful for since they are not brand new. These are great companies who stand behind their products and support their customers.

You'll see get better performance, linearity and repeatability with an electromagnetic weigh sensor which cost a whole lot more, and takes us back to the “Does it really make a difference?”

I have received a lot of feedback asking “What am I thinking and why worry about it so much?”. Well the answers are simple in my mind. The pursuit of perfection is why I got into the hobby of shooting, smithing and reloading. It’s fun to be able to make one hole. When I screw up and miss blow a group, I like to be able to prove to myself that the variation was the shooter,me) and not the other variables. For me this is fun.

The other concern I have and wanted to understand is regarding loading pistol rounds where a tenth of a grain is much more of an issue than with my 25-06. My brother and I load 17 Mach IV,17 Fireball) and 460 Rowland cartridges which are by nature fairly hot and sensitive to load variation. A couple of tenths of a grain will make a significant difference. ,If you haven’t shot a 460 Rowland in a 1911, you have to try it, Clark makes great barrels and they shoot great. http://www.clarkcustomguns.com/rowland.htm )

I have purchased an Acclab VIC 123 which reads to .01 grains and will continue this crazy pursuit of one hole groups !!! If there is interest I’ll write back later with more information and some statistical comparisons,GR&Rs for you quality geeks) of these measuring tools. Thanks to all who replied and contributed. This is a great community and I am proud to be a part of it.