How do I "calibrate" an rcbs scale?

[Davo]

I just got an rcbs 505 scale, but it did not come with instructions. It did come with some 7.5 shot, which I assume goes under the pan. My question is, how do i zero out this thing? I have no experience with any scales, except from chemistry and A&P in college.

 

[ReloaderFred]

Set your scale on a steady, level surface and with it properly assembled, put the pan in the holder, empty. Let the scale balance out and then adjust the leveling screw until the arrow is aligned with the zero on the scale.

These instructions are from memory, since I gave my balance beam scale away several years ago, so I may have forgotten something.

Hope this helps.

Fred

 

[Davo]

Thanks Fred, so I guess you want the scale with the brass pan, to be at zero, when the scale is zeroed out. Makes sense, ill give it a try.

 

[The Bushmaster]

You got it right Reloaderfred. I still have my 5-0-5. I use it to check the accuracy of my RCBS electronic when I loose confidence in it...Niether have been off though...

 

[Davo]

Fred when you say leveling screw, do you mean the wheel on the base of the scale?
I just weighed some bullets, and they all matched up, though varying within a few tenths of a grain, I also weighed 3 pennies, I got 38.7gr, 38.3gr, and 38.6gr.

 

[Mal H]

That's correct, Davo. You adjust using the thumb screw on the base.

The shot is to adjust the pan holder weight to get the maximum adjustment distance out of the screw. That is, you add or take away a few bits of shot from the underside of the pan holder (usually a screw holds a small pan under there with the shot in it). The ideal is to be zeroed on a perfectly level table with the screw in the middle of its travel. Normally, you won't have to do any adding or deleting of weight - they usually have it very close from the factory.

 

[wingman]

Correct info., also check each time you reload, dust, vibration can change zero., After use i cover mine with plastic.

 

[TooTaxed]

The instructions provided above are fine for initial empty zero...but you should still calibrate with known weights roughly near the powder charges you will be using. All scales will "zero"...but you'd be surprised at some of the operational variences!

RCBS sells a set of weights for about $25...but you can save bucks by having a friend with a calibrated scale provide you with a variety of known weights...for example, thick copper wire pieces filed to 1.0, 2.0, 3.0, 5.0 grains, plastic bottle caps or corrosion-proof metal in 10.0, 20.0, and 30.0 grains.

 

[Ol` Joe]

I just weighed some bullets, and they all matched up, though varying within a few tenths of a grain, I also weighed 3 pennies, I got 38.7gr, 38.3gr, and 38.6gr

Davo,
You`ll find most objects, bullets included will vary a couple tenths in weight. Grains are very small wgts and manufactureing tolerances are not normally held that tight, even Sierra Match Kings will vary by a .3 gr tolerance according to their specs.

The pellets you found with your scale should be returned to their place in the platen and left alone. They help with the beams balance and are there for a purpose. Zero the beam to level with the pan in place by turning the screw leg ajustment. Set the scale up on a even level surface and away from breezes, magnetic sources (floresent lights, static produceing material, ect) and where it wont be bumped or knocked accidentally. The other poster suggesting check wgts is a very good idea. RCBS and Lyman both make them and prices are reasonable. If you have any questions or problems with the acale call RCBS they have the best customer service in the business and will be glad to send you a manual or discuss your problem over the phone.
1-800-533-5000

 

[Mannlicher]

New US coins can be used to some extent to calibrate your 5.0.5 scale. For example, a new nickle weighs 5 grams, or 75 grains. A dime weighs 2.268 grams or 35 grains. On my RCBS scale a new dime weighs 35.2 grains, or fairly close.
I always zero the scale, then use some calibrated weights that I bouoght online, but the coins come pretty darn close.

 

[Mal H]

Mannlicher, I'm going to have to disagree with the statement "the coins come pretty darn close." Even new coins can vary quite a bit, they aren't in any way a good calibration standard in the truest sense of the word 'calibration'. I would agree that using a coin that has been weighed on another accurate and calibrated scale would make a good check weight, but the coins in general, without prior weighing, are not good check weights.

Oh, and 5 grams = 77.2 grains, that's a big difference from "75 grains" in the reloading world.

 

[Johnny Guest]

Scale calibration check weights

I have a small set of RCBS check weights and it is amazing how much the price has climbed in the past twelve or 15 years.

Nowadays, if I feel the need to check calibration of my scales, rather than dig out the weight set, I reach up on the shelf and take down a box of Sierra or Hornady match bullets. I figure if three to five each of MatchKing .30 cal 168 gr and .223 cal 55 gr. weigh within plus-or-minus two-tenths of a grain (0.2 gr) I know two things:
First, my scale is dead on, and,
Second, these are very uniform, high quality bullets.

Best,
Johnny

 

[Mannlicher]

Mal states, with some correctness:"Oh, and 5 grams = 77.2 grains, that's a big difference from "75 grains" in the reloading world."

my mistake in typing. Actually its 77.16, and a few more decimal points to boot.

But my point is still valid, Using something you have onhand, like a coin to at least check for gross error, is better than having nothing. Frankly, a LOT of guys don't have lab grade test weights sitting around, even in the 'reloading world'

 

[Bronson7]

To minmize variances, I find a check weight close to my target powder charge and set the poises to reflect the check weight. I put the check weight on the pan, wait for it to stabilize and zero out the scale. I remove and replace the pan several times to make sure I have good repeatability. Then, I set the poises to reflect my target weight. I do this because I know that scales can vary in accuracy throughout their range. In other words, I calibrate my scale to the range I'm using. To me, this is a more accurate way to do it. Takes less time to do than explaining it. I only use check weights intended for the purpose. The practice of using coins, soda cans and dead cock roaches as standards, goes against my grain . Weighing something on someone elses scale and using it as a standard on yours, well, I'm not keen on the idea but to each his own.
Bronson7