Problem with RCBS 505 Scale


December 2, 2012, 08:28 PM
So I've been using a RCBS 505 scale for the last few years. I went down to reload tonight and am having a problem with it. I had this problem in the past once before and I tried it out again the next day and it worked fine.

The problem I'm having is when I try to zero the scale it seems like it's way off. So I adjust the height of the scale to zero it and once I get it zeroed I take the pan off and put it back on, and the scale has a different reading. I can then take the pan off and put it back several times and the scale has the same reading, but the marks will no longer be zeroed the mark on the beam will usually be higher reading like something is in the scale. I will then zero it again to these marks. Then once I remove the pan and put it back on, the beam will be quite a bit lower. It's just a back and forth cycle and I can never get it zeroed so that it will read the same thing after removing the pan and reinstalling it.

Anyone had this issue? Any tips to get it fixed? Having had this issue, it always makes me scared it's going to act up while in the middle of loading and throw my loads off, but so far I've been pretty lucky with that.

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December 2, 2012, 08:51 PM
I have just had a similar issue with a 5-10 I just borrowed. Playing with the height of the scale didn't work as well as I hoped. Now I don't know if the 505 is the same as the 5-10. But what I had to do was unscrew the screw in the center of my pan to expose the BB's underneath. I had to add weight to get it close then I could make minor adjustments with the feet.
I used a tiny bit of clean sand I had around. Didn't have any bb's without taking skeet or bird shot apart.
I first added it to the pour pan till I was close to zeroed. Then removed the screw and dropped it in. Replaced it all and it seemed to zero and repeatability was good.
Hope this helps.

December 2, 2012, 08:54 PM
Do you have the scale near flourescent lighting...within a few feet? The directions state that this can mess with the magnetic dampening of the scale.

If not near flourescent lighting, is there an inconsistent draft of air in the area of your reloading bench? If the area has an inconsistent draft, you might not have this problem but once in a while.

Have you taken the scale apart and put it back together again? This sometimes will fix things when the problem isn't apparent...such as dirt or grime in the working parts of the scale.

I have experienced similar occurrences with my 505 scale, but nothing that wasn't remedied by eliminating moving air from a fan or taking the scale apart.

If these don't help, call RCBS.

December 2, 2012, 10:35 PM
Have you tried cleaning the "V" notches of the agate stones?

The triangle knife edges pivot on the notches and if dirt/debris accumulate in the notches, it may affect the scale's ability to maintain zero.

Also, the agate stones must "free float". If the cleaning of the "V" notches don't resolve your drifting zero problem, remove the stone covers with a Phillips screwdriver and check for dirt/debris that may be keeping the stones from free floating.

December 3, 2012, 02:48 PM
Is it near an electrical motor, tumbler maybe? Motors produce magnetic fields
Lighting ficture?
Is the table it's on 100% stable? Even a very small wobble will cause this.
Air flow such as fans, an open window, and air ducts even when the heat / AC isn't operating can still cause rising and falling air currents.
Earth quakes, even very small one's will effect a balance beam scale.

I have the same scale and experienced the same thing not too long ago. I never did positively identify the problem, but it hasn't happened since. The only thing I could blame it on was an earth quake that occured that evening and within the time frame I was experiencing the problem. Since I had never had any issues with my scale before, I think a quake may have been the culprit. After shocks can go on for minutes, even hours. Check the earth quake site to see if you were near one during the matching time frame.


December 3, 2012, 02:54 PM
As noted, clean the bearing with alcohol & Q-Tips.

Then make sure the beam is centered between the two side plates and not rubbing on one end or other.

Also use a bubble level to insure your bench is level from side to side and end to end.

There should never ever be a reason to take the shot cup off the bottom of the pan hanger and add or subtract shot.

That is how the scale is accuratly calibrated at the factory, and unless the beam starts growing longer, or adding excess body fat?

There is no way for it to ever change again.


Maj Dad
December 3, 2012, 03:02 PM
+1 on bds - cleaning the v notches & making sure the beam moves freely. I use a clean toothbrush or other small brush & clean them frequently (every session would not be too much). They will get small dust particles & that can bugger things up and drive you nuts. Drafts and strong fluorescent tubes will also affect it as mentioned - I have to turn off my little fan when using it and my bench light is a 13w cfl that I can elevate ~2-3' above the scale.

10 Spot Terminator
December 3, 2012, 04:34 PM
All good tips here on leveling, cleaning the stones and stone cradles , checking the beam itself to make sure it is free from obstuctions and so on. I too do these things and add one more item by lightly polishing the pivot arms on the beam. Also after any movement/redjustment of the weight tabs I lightly tap my finger a few times ever so gently on the beam to settle the weights into the grooves and then proceede to adjust my zero level. Once this is done I lightly touch the pan and let the beam settle and recheck the zero and relevel and repeat if needed until it returns to zero say 3 times in a row. I call this "settling in" so all parts are finding their happy spot .

December 3, 2012, 11:49 PM
My used RCBS is better after removing the stones and really cleaning with break cleaner. I also polished the edges of the knifes.

December 4, 2012, 06:56 PM
"I also polished the edges of the knifes. "

That can be good if you don't round the edges.

I grind a little relief on both ends of the knife beam, at a very slight angle towards the beam, to reduce any end drag on the metal bearing clips.

December 4, 2012, 10:00 PM
ranger, that suggestion is a new one to me and makes total sense.

I'd noticed the 505's triangular knife ends can sometimes touch the metal caps and impede the beam's free movement, but never thought of reshaping them a bit. I would just nudge the beam back away from the end caps.

December 4, 2012, 10:22 PM
okay, this will sound weird, but it works, really well. The beam bearings needs to settle in each time after getting knocked around by removing and replacing the pan. The best way to do this is by controlled vibration.

I stole the wife's egg vibrator, cleaned it up real good (ewe), then strapped it to the side of the base with a rubberband. I use the remote switch to pulsate the scale for a second or so, and I get uber consistent results everytime.

After getting laughed at a few times, I figured to use a small aquarium airpump plugged to a wired "thru" switch to acheive the same results, without all the comments from the spouse and guests, and questions from the young children. The wife was happy to get her toy back, the fish get a powerhead , and dad can keep reloading.

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