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strange scale behaviour

Posted: Fri Jul 08, 2011 8:35 am
by bow shot
I was naughty ans posted this in "General Reloading" too...

Anyone run across this using an RCBS 10 - 10?

1) you are loading in a breeze/air curent free room
2) you check zero/level before loading and do not move the scale.
3) the scale pivots points "seem" very clean

4) you I throw a charge, trickle it, and get a perfect weight (in this case 26.5gn). Then you dial the adjustment barrel up 0.1gn (say, up to 26.6gn) for the next charge but go back, re-weigh the original (26.5gn) charge, and re-weigh it and the beam indicates a perfect (?!) reading again as if the powder in the pan added to itself :duh: .

Comments? Ideas? :huh:

Makes me wonder how much of my unusual test group readings are owed to this behaviour? I know that in ladder tests, I'll can sometimes see as much as see 1" change in POI with as little as 0.2gn powder change...

Re: strange scale behaviour

Posted: Fri Jul 08, 2011 8:43 am
by RAMOS
Bow Shot,
I responded in the "General" section. Now quit being naughty, Christmas is less than six months away!!!
Jon

Re: strange scale behaviour

Posted: Fri Jul 08, 2011 8:57 am
by bow shot
Yeah, I hear Santa hates attention hogs, LOL!!

Re: strange scale behaviour

Posted: Fri Jul 08, 2011 10:48 am
by Trent
I've switched to a RCBS Chargemaster 1500, but here is something that I noticed with my pan scale. If you don't do everything the same you can end up with inconsistent measurements. When I would dump the powder in the pan I would then hold the arm down and then let the scale balance out. If I just dumped the same powder charge in there and let it settle I would get a slightly different reading. I was very meticulous about preparing and cleaning my scale and I would still see these fluctuations. Just like your powder measure, you have to do every motion the same each time.

This was with a RCBS pan scale. Maybe a Redding would be more consistent.

I haven't looked back since switching to the Chargemaster and I have much more confidence in my charges since it takes the human aspect out of the picture for both charging and weighing.

Re: strange scale behaviour

Posted: Fri Jul 08, 2011 11:21 am
by RAMOS
Trent, I hold the pan under the measure and gently shake the powder level. Then I place the pan on the scale with the handle in the same place each time. I then trickle it up to charge weight. I don't like touching the beam as there is a chance that it could settle in to the bearings differently. The other thing I do is to place the scale itself in the same place each session since I know it to be level front to back and side to side. If I could afford a lab quality electronic scale I would consider it. The ones most of us can afford do little to fill me with confidence. I would rather have the resposibility on myself and a quality mechanical device than most of what is being offered to the reloading community. I suppose I'm behind the times, my scale should be eligible for Social Security in a few years but, we have a good relationship. Sounds like what you are doing works for you so, by all means, keep doing it!
Jon

Re: strange scale behaviour

Posted: Fri Jul 08, 2011 1:54 pm
by bow shot
'Funny you should mention that, about how the powder is situated in the pan...
At 0.0X grains, I could see it "looking" heavy to the beam if the powder in the pan was all heaped toward the user's right... or light, for vise versa. 'Or in a heap vs in a level pancake shape. Hmmm.... time to tinker....

Re: strange scale behaviour

Posted: Sat Jul 09, 2011 4:01 am
by GaCop
Unless you get a lab quality scale, the accuracy of reloading scales is around 1/10th grain. A variable is built into it right from the start. My 10-10 is finickey to the point I have to turn off my ceiling fan and a de-humidifier or the beam will fluctuate. I've run into the same thing with a Dillon and an RCBS 505. My PACT electronic was a royal pain, any air currents would make it go wild and it went belly up in less than a year. We won't even talk about PACT customer service, or lack of.

Tom

Re: strange scale behaviour

Posted: Mon Jul 11, 2011 5:40 am
by bow shot
Yeah, I have to do the charge throwing in a zero-air curent room or its all in vain. Super-drag when its over 90 degrees... like its been all week!!

I did a bearings swab with a lint-free wipe. There was nothing on the surfaces that took a good picture, jut the tiniest amount of air-borne, fiberous type lint? That seemed to help, the difference in beam travel seems a tad more obvious now in the 0.1gn region, though it is still pretty darn tiny

On we go, one more thing to obsess over, :wall: !!

Re: strange scale behaviour

Posted: Mon Jul 11, 2011 9:39 am
by RAMOS
I agree, air currents are a PIA! In the winter, I just weigh charges in between heater cycles. It takes longer but, imagine what effect a dripping nose would have on a powder charge!!! We built an insulated room inside an insulated shop and that has been a big improvement. No drafts and fairly stable as far as temperature. For anyone considering something like this: My room is 8x12, 3/8" MDF inside and out. It has general storage on top that made it a little easier to give up the floor space. All told, lumber, insulation, pre-hung door, lighting, heat, paint, etc, we spent less than $600 using our own labor. Thought about doing it for years, sorry I waited so long.

Re: strange scale behaviour

Posted: Tue Jul 12, 2011 9:15 am
by bow shot
I'm thinking of doing a similar thing, we have a closet available now that the bows are grown and gone, and my handloading space requirement is pretty tiny... just using the dinette table now.

The only hitch is my wife would kill me. That would be justifiable though. I'd kill me, but that's against the law (of God and man), and beside, why ruin someone else's fun?

Re: strange scale behaviour

Posted: Tue Jul 12, 2011 8:00 pm
by RoadKill
The scales in the lab of the dyehouse I worked in were used to weigh dye in grams to four decimals. They are surrounded by glass with horizontally sliding access doors on both sides. You trickled on the last bit then closed the doors to block any draft from affecting your final call. They were certified very accurate and very expensive but the money alone didn’t block the barely perceptible breeze.