Scale variance for 45 ACP reloads

[nosmr2]

I am attempting to load a batch of 45 ACP. I have Speer 230 grain lead round nose bullets and unique powder. I am working with a Lee Turret press and the Lee auto disk. I made a batch a few days ago and everything lined up. However, its not going so smooth today. I recently purchased a RCBS 502 scale from ebay to verify with my Frankford $25 digital. I did ensure the 502 was leveled and zero'd. I calibrated the digital per instructions. They matched last week when measuring. Both showed 5 grains. Not the case today. The digital scale shows 5.0 grains the RCBS shows 5.5 grains. The lee auto disk is set at .66. Any suggestions, or which scale should I trust?

The unique load data for 5.5 grains has a min OAL of 1.27, while my Lee book recommends 1.190 for 5.0 grains. I had been setting them at 1.20 with 5 grains.

Any help is appreciated.

 

[earplug]

Use one scale

I tried messing with two scales as your doing. It like trying to keep time with two or more mechanical clocks.
I would use the RCBS scale. Find a spot on your bench to use it. Mark its out line on the bench and always use it in the same spot.
If your reloads from your powder measure checked with your scale work fine don't worry.
If you do the same thing each time you will duplicate the same load.
Its like cooking. Anytime you vary a component or how your measured the components you open up more variables.
This is another reason why the various reloading guides have different starting and max loads.

 

[GCBurner]

I generally trust the balance beam over a digital, but that's just based on my experiences. If you have a test weight for calibration, try it on both and see if it matches, or just weigh something like a dime several times in succession to check consistency. A cheap digital scale I used to have would give five different results for the same test weight weighed five times.

 

[nosmr2]

With my 20 gram test weight I got 309.4 grains on the RCBS & 308.7 on the digital.

 

[Steve C]

The digital scale shows 5.0 grains the RCBS shows 5.5 grains. The lee auto disk is set at .66. Any suggestions, or which scale should I trust?

You don't say how many samples you took to weigh on both scales and if you used the same throw or different powder throws on each. If you left the powder in the hopper for a while you will find it often will settle a bit and the first throw may be a bit heavier. You really need several samples using the same powder throw on both scales to see if they're going to agree.

Personally I trust a balance that is a simpler device before I trust an electronic scale. I've had too many electronic devices quite working properly for a time for no apparent reason to trust them much.

OAL is only important with the .45 acp in determining the round will not engage the rifling before properly chambering. Usually I simply seat a RNL bullet so the case mouth is at the end of the straight side and start of where the bullets nose tapers. The OAL is what ever it winds up at.

 

[mbruce]

Not sure if anyone can give you an "in good faith" answer - as both can be off and it's one of those things where you have to be there to really know. I would read the posts from the thread below and do what Mr. rfwobbly mentions in his post ("pistol sized" check weights).



http://www.thehighroad.org/showthread.php?t=567322

 

[squarles67]

You also need to keep an eye out for "other factors" that might be causing the variation. When I first started this a few years ago I could never get a consistent powder drop. Sometimes they would be dead on other times not so much, it turned out to be the draft coming from the air conditioner vent above my bench. I turned the register around the other way and suddenly I was getting more consistent weight readings.

I'd trust the beam scale over the digital any day

Unique out of my pro auto disc has always varied a couple of tenths

 

[oneounceload]

Get your scale off your bench and place it somewhere not affected by the vibrations of working the press. Mine is on a shelf right above the bench so it is at eye level and working the press has no effect.

 

[918v]

Either scale needs to be calibrated every time before use.

 

[nosmr2]

Actually, both scales are on my computer desk, not the reloading bench. The bench has sliders and lives in the closet when not in use. Apparently, reloading bench does not go with any decor, according to the wife.

 

[nosmr2]

When you say calibrated, does that mean to zero balance the beam scale by leveling it? If so, I do that prior to each use.

 

[C.F. Plinker]

With my 20 gram test weight I got 309.4 grains on the RCBS & 308.7 on the digital.

At 15.43 grains per gram the reading from the digital scale was closer to what the calibration weight should weigh--308.6 grains. I have two balance beam scales (a C-H oil dampned scale and an RCBS 505) and two digital scales (the cheap Midway and the original Dillon). When weighing powder charges I use the C-H and set it to the desired weight, put that weight in check weights in the pan, then zero the scale using the adjustment screw in the base. This way the zero is made at the weight I am measuring and , because it is using the check weights, is repeatable.

 

[918v]

And the digital? Do you calibrate it as well? Maybe you need fresh batteries?

 

[nosmr2]

Yes, calibrated this morning. I don't know how old the batteries really are, but I received the scale in November and have been using it since the first of the year.

 

[rcmodel]

Actually, both scales are on my computer desk,

Take them off the computer desk to the kitchen table and try it.

You may be getting magnetic or electrical fields from the electronics or monitor interfering with one or both scales if they are close to a computer monitor or power supply.

rc

 

[rfwobbly]

You're getting some great input here.

In addition I could only add...

• Buy some check weights in the weight range in which you reload. It does no good to zero the scale with a 20gram weight (308.65grains) unless you are reloading something that takes powder in the 300grain range.

Why? I sincerely believe that balance beams can be inaccurate, but when they are, generally are linear in their behavior. That is, your RCBS is 99.7% accurate at ALL readings. Digital scales on the other hand work by having a mechanism stretch a membrane through which an electrical current is passing. Therefore it must be prone to environmental variations, mechanical disturbances and electrical irregularities. Knowing that tidbit, I highly suspect some cheaper digital scales are most probably not linear.

On more expensive digital scales this is probably well understood and very well controlled. But I have sneaking suspicion that the cheaper digital scales leave these "features" out. Sort of like buying a discount car only to find out it doesn't have a radio or heater. So that although the scale "zeros" at 20 grams, the readings at some places could be high and at others low. Not only that, but as the membrane stretches, the shape of the accuracy curve changes over time.

Now let me make VERY clear, I have no proof of this, it is merely my deep suspicion based on my education and experience. And too, please understand I'm not saying ALL digital scales are this way. But obviously, the less you pay for a digital scale, the more suspect your scale must be, by its very nature.

All the best.

 

[rfwobbly]

Dup

 

[cheygriz]

Again, wobbly's right!

there's * ONE * way, AND ONLY ONE WAY to tell if your scale is weighing accurately.

And that is to get a set of Scale check weights.

You can buy an excellent set for less than $30. It's the cheapest insurance there is!

 

[nosmr2]

Thank you all for your responses.

To answer a few previously asked questions:
I took at least 10 samples. I weighed the identical sample on both.
No wind in room, heater and fan off.
I have not tried the scales on the kitchen counter away from potential monitor interference, had job interview to attend.

Long story short, I found the RCBS check weights (in the weights I need) across town at a store I planned on shopping tomorrow. I will keep you all posted, in case you are following my progress.

 

[tickfarm]

I have the RCBS 1500 digital scale and powder measure. After I calibrate the scale per instructions, I always weigh a known weight. Usually one of the bullets I'm using. I know they don't all weigh the same but it's close enough to show me the scale is accurate. You can also use one of your calibration weights.

 

[birddog]

With my Lee Turret, the .66 disk gives me exactly 5.0 grains of Unique. The .76 disk gives me exactly 6.0 grains of Unique. Been using this setup for years, verified on two scales.

 

[rfwobbly]

This younger generation is sure getting soft

I have not tried the scales on the kitchen counter away from potential monitor interference, had job interview to attend.

What!

Since when is working more important than reloading? I can't believe I'm reading this! One more statement like that and we might have to take away your reloading permit, AND your Dillon calendar!!




Hope you get the job.

 

[nosmr2]

Alright, today's update.

Picked up the RCBS weight set. Zero'd the beam scale and calibrated the digital. Both read the same with all the known weights. I didn't have any powder out to measure, but that would be measuring an unknown. I wanted to measure these. Go figure that they matched. I kinda trust the electronic from Friday, since I have measured quite a few of these loads at .66 on the autodisk with the Unique powder before. Not sure why it would start dumping more powder with everything else being the same. Maybe the beam wasn't leveled, like I thought it was, and rechecked multiple times. I don't know......

 

[mmitch]

Using the auto-disc set-up, I have learned to throw 2-3 initial charges before I'll take a measure of the thrown charge. I check this throw about every 10 charges, more often if I have any question about whats dropping.
On the Lee Turret press, I am, caliber by caliber, upgrading to the Pro Auto Disc and ditching the disc and using, instead the micrometer charge bar Lee sells.
This is consistent, + or - .1 gr.
I use my RCBS chargemaster scale and will cross-verify with a seperate RCBS 500 electronic. The 500 gets a new battery every week, or when I begin reloading after taking time off.
If things get screwy, I will add a balance beam scale to the process, to see what's what.
Monitors, plug-in strips, flourescent lighting, any flowing electrons, may affect an electronic scale.
Blowing-up guns is expensive, becoming meticulous about consistent loads is one way to avoid that kind of tragedy.

Mike

P.S. when you stroke the ram to throw a charge, try to be consistent in your stroke --- changing technique from throw to throw can yeild some variance.