RCBS 5-10 scale accuracy at the low end?

[MRM]

I bought a used RCBS 5-10 scale a couple of years ago and have used it successfully for loading a thousand or so rifle rounds. It has given me no reason to question its accuracy to date, but I have always been measuring 20+ grains.

Recently I started loading 9mm. I purposely started with HS-6 as it calls for almost twice the weight as the other pistol powder I have on hand, Tight Group. That said it is around the 4 grain mark, well below the range I have been dealing with for rifle.

Everything looks good, it is consistent and the volume in the cartridge looks the same for all loads. Just want to do a gut check to see if anyone has any warnings before I test the rounds.

Thanks,

MRM

 

[hobit]

I've recently purchased a used rcbs 10/10 that was dirty to say the least, through research on cleaning these scales, including the older 5/10, they seem to be highly thought of. If you keep yours clean and the knife edges are sharp you should be good to go but as was pointed out in my 'how to clean thread', test/check weights are your friend. Hope this helps.

 

[dead meat]

I got a set of test weights years ago, not real expensive. I use them every now and then just to be sure.

 

[jethunter]

Weigh out 20 gr of powder on your scale and set it aside in a separate container. Then take powder from the 20 gr container and weigh it in 2.0 gr increments. It should work out that you get very close to 10x 2gr increments from the 20 gr pile, and that tells you the low measure accuracy is comparable to the heavier weight accuracy.

 

[Varmit]

I use Nosler check weights. Good enough?

 

[MRM]

Thanks for the info all. I’ll try to source a set of check weights. In the quick search I just did it was the classic US cost times 4 to get it in Canada…

I’ll try the splitting a known charge into increments approach tonight. Disappointed in myself that I did not think of that.

Thanks again.

MRM

 

[VinnyQC]

Thanks for the info all. I’ll try to source a set of check weights. In the quick search I just did it was the classic US cost times 4 to get it in Canada…

I’ll try the splitting a known charge into increments approach tonight. Disappointed in myself that I did not think of that.

Thanks again.

MRM

I got my set for 10$ on ebay. 10mg to 100g, so plenty to calibrate any reloading scale.

 

[fingers284]

One thing to remember with any of the balance beam scales we buy for a few bucks may not be accurate to your test weights when you get them. They are built to fit into a specific price range and simply be a "comparison" tester not an "absolute specific" weight tester. This is why every loading manual and powder manuf. specify a much lower "starting weight" for every load they publish...they have no control over the accuracy of a "production line" manufactured beam scale so always error to the safe side for a beginning load.

It is a popular misconception that starting loads are only listed to allow for different clearance allowances common to different gun manufacturers, which holds true to a certain extent but the biggest reason for starting loads is the difference in scale quality from one manuf. to another. Its not the gun manuf. that publish the loading manuals, its the bullet & powder manuf. that do and most often their the ones that put their name on the loading scales as well...they know the limitations themselves.

 

[Third Rail]

If anyone knows of some consistent, KNOWN weights under 10 grains that can be used as a reliable reference, I'm all ears.

I went through this a while back and while using the Google machine, found that some reloaders went so far as to weigh primers. A CCI Large Rifle Primer weighed 5.3 grains. Low and behold, that is what it weighed on my Lyman 1000.

I've checked larger weights and my scale comes within a few tenths of a grain. Close enough for my measuring.

Anyone ever confirm the accuracy of those Ebay check weights?

 

[TrxR]

Try cambridge environmental. They might have some small check weights .