Daily Bulletin

[clowdis]

I was just reading Bill Schnauffer's topic on the new Gempro 250 scale this morning and had a question about his comparitive measurements between his Pact and the new Gempro. He states "During the throws, if the Pact scale read 1/10th over/under, I didn’t make any correction. I just waited until it stopped dispensing and the transferred the charge in the pan to the pan in the GemPro 250". My question is why would you throw known incorrect measurements and compare them on another scale? Wouldn't it have been better to throw "same" measurements on the Pact and then compare them on the Gempro? I don't think he was casting stones at the Pact but I don't see this method as elevating the accuracy of the Gempro either.

 

[Taildrag15X]

I agree, didn't seem right to me either.....I was also wanting to know about the warm up time he gave the PACT scale as well as the GemPro. I know I leave my scales (both 1/10 & 1/100 gr.) on in a controled atmospheric room so that when I want to use it I can knowing that it's not going to drift during warm up.

I find that if I throw from the PACT 1/10 gr. under what I want that every once in awhile (1 out of each 18-20) I'll get the dead on load I want once I transfer it to the 1/100 gr. scale, which is why I double weigh and use the 1/100gr. scale.

 

[CoverDog]

Taildrag15X & clowdis.....This was my first attempt at presenting an article for review by other members, and I will explain what I did.

As stated in the article I leave my scale(s) up and running all the time 24/7/365. My reloading room is in a finished basement room which has central A/C & Heat like the rest of the house. Relative Humidity is adjusted seasonaly.

After calibrating both scales and programming the Pact Dispenser to the set amount I began to let it throw charges. I am not an electrical engineer, and my statements are based on what I presume is happening. The Pact dispenser receives the input from the scale or vice-versa by way of infrared signal. When the scale signals the dispenser to slow down and then stop throwing a charge, I have to think that the scale has reached the "set" amount of powder from the signal it has received from or sent to the dispenser. At this point I transfer what is in the scale pan on the Pact to the GEMPRO 250 and recorded the data.

If the thrown amount is not exactly the set amount I have to assume that either the scale is inaccurate or the dispensing program is wrong. I don't know what other conclusion I should draw. In the article I said the Pact has been my go to "combo" for almost 10 years and my only digital "scale only" since 1994. With this comparison I was able to see how “accurate” my reloading with the Pact combo has been when using thrown charges.

I am waiting to see what the results of the editors testing will be.

Editor’s Note: In this review, the GemPro 250 is used to confirm the weight of powder throws from a PACT Digital dispenser. However, the reviewer did not have a laboratory-grade scale to test the displayed weights from the GemPro 250. We have another GEMPRO 250 on order from Amazon.com. When it arrives we will do a comparison weighing test, using a Denver Instruments Lab Scale as the control unit.

Thanks for your input,

Cover Dog

 

[clowdis]

CoverDog,
Congratulations on having your first article printed. I admire your ability to take the time to do a write up like this and send it in to the editors, thank you. I use a RCBS Chargemaster for most of my reloading and with it being a .1 grain scale I realize that it can be within .05 under and .04 over and still register 65.0 grains (or whatever weight). So I have loads ranging from 64.05 to 65.04 grains or a range of .09 grains. Since I shoot prone and not benchrest this much accuracy is acceptable to me and shots are well within X ring (1 minute) accuracy at 1,000 yards. But I think my approach would have been to weigh the charges all at 27.7 grains on the Pact and compare those on Gemtech. I think that would have given a better idea of the difference in powder weight charges between weighing in .1 grains vs. weighing in .01 grains. Thanks again for the article.

 

[jhord]

I've been eyeballing that scale for a few months on Old Will Knott scales. (who I've bought shipping scales from in the past, no problems) I think I'm going to get one and compare it to my RCBS 750, should be an improvement. Q for the Boss, if I follow this site's Amazon link, and Amazon then links to Old Will Knott... does this put a bit of $$ in this site's coffers? Or is there another way?

 

[Forum Boss]

Remember Cover Dog's purpose in the testing was to see if the PACT was actually throwing correct charges -- and how often it was doing so. Now, if we were actually loading ammo, of course we'd toss a visibly high/low charge back into the hopper.

I want to thank Cover Dog for taking the time to do this write-up. He put a lot of effort into the review. As he noted, we ordered what, apparently, was one of the last units available on Amazon. We will cross check it with a lab scale and tell you the results. But... I am encourage that Cover Dog's check weight came up exactly the same numerous times. I have a PACT scale (not dispenser), and I have observed that it will drift up to 0.3 grains over time -- even after a long warmup.

 

[nhm16]

Compared to the AY-123/VIC-123/MXX-123 clones, doesn't the GemPro also use a strain gauge weight cell as well? I can't imagine a scale that costs less than $200 using anything more advanced. I bet that the reason that it is less sensitive to electronic interference compared to the Sartorious triplets is that it runs on batteries (i.e. cleaner power).

 

[CoverDog]

nhm16......although the GEMPRO runs on 4-AAA batteries I only installed them to add a little weight to the unit. During my testing I used the 110v power supply that was supplied. I also always use an in-line clamp on magnetic (ferrous) noise filter.

Here is some info I found when I Googled German HBM true-division sensors:


The German HBM true-division sensor gives a whole new meaning to calibration. This machine allows calibration force transducers on site from 2.5 N to 5 MN. The machine also boasts a measurement uncertainly of just 0.02 percent. The units force comes from a hydraulic power unit, which is required for calibrating the machine. During the calibration process, the machine’s force transducer sends out signals that are then compared to the integrated reference transducer within the machine. This piece of equipment has been specifically designed to give maximum force and can calibrate the compressive and the tensile force transducers.

This should give you an idea of the technology behind the German HBM true-division sensor. This latest piece of equipment from Germany’s HBM only strengthens the fact that this calibration lab was the very first one to be accredited by the prestigious German Calibration Service back in 1977. German HBM offers customers the most trusted and needed measurement products and services needed for their force measuring. The company provides a wide range of solutions to help customers with all their force measurement needs, covering all the bases in the process.

 

[Taildrag15X]

CoverDog, I'd like to thank you for the article, wasn't bashing you, or your set up, just wanting to know about the PACT warm up, which you have answered, same as mine, on 24/7.

I want to say that if I struck any nerve, with anyone over my comments/question it was not meant to be, it was only a question not covered in his article.

I'd like to thank him for the time he commented to do the test and write the article.

 

[TonyR]

Maybe I am missing something, but it don't recall seeing any mention of calibration weights in the discussion so far. Both of my scales use calibration weights in the set up process, but I also have weights close to the weights of the powder charges I use to check the consistency of my scales during a reloading session. Old Will Knotts sells weights to meet various precision standards, some of which are very inexpensive. Comparing the values given by different scales for the same physical object of a known weight would appear to be a necessary step in any comparison method.

 

[Taildrag15X]

In the article both scales were calibrated with the supplied weights for each scale, the article is here:

http://bulletin.accurateshooter.com/2011/08/review-of-the-gempro-250-scale-from-my-weigh/

 

[TonyR]

I see the part about calibrating the individual scales with their prescribed calibration weights. I am questioning a comparison of two scales without measuring the same object of a known weight at the same time on both of them. Electronic scales do drift despite all of the useful steps that have been mentioned here to minimize the drift. I have a little 50 grain calibration weight that I use during a reloading session and my scale can weigh that object within an 0.04 grain range during a loading session despite all of my best efforts to prevent it.

 

[CoverDog]

TonyR.....The GEMPRO 250 comes with a 20g ASTM class F2 calibration weight. The Pact uses both a 20g and a 50g calibration weight during it's calibration process. Since the GEMPRO scale only weighs down to 2/100th's of a grain, the 100th's digit will always be an even number, even thou a 20g weight when converted to grains will weigh 308.65grains. My GEMPRO calibration weight shows 308.64 on the scale screen.

Using the GEMPRO I have also weighed the 2 calibration weights (20g & 50g) from the Pact and added a little piece of tape on the bottom of each so they weighed their respective weights on the GEMPRO.

In conclusion we are comparing apples to apples.

Added: I also have a complete set of Class M2 calibration weights I use from time to time. Weights included: 100g, 50g, 20g( x2 ), 10g, 5g, 2g( x2 ), 1g, 500mg, 200mg( x2 ), 100mg, 50mg, 20mg( x2 ), 10mg

 

[TonyR]

TonyR.....The GEMPRO 250 comes with a 20g ASTM class F2 calibration weight. The Pact uses both a 20g and a 50g calibration weight during it's calibration process. Since the GEMPRO scale only weighs down to 2/100th's of a grain, the 100th's digit will always be an even number, even thou a 20g weight when converted to grains will weigh 308.65grains. My GEMPRO calibration weight shows 308.64 on the scale screen.

Using the GEMPRO I have also weighed the 2 calibration weights (20g & 50g) from the Pact and added a little piece of tape on the bottom of each so they weighed their respective weights on the GEMPRO.

In conclusion we are comparing apples to apples.

Added: I also have a complete set of Class M2 calibration weights I use from time to time. Weights included: 100g, 50g, 20g( x2 ), 10g, 5g, 2g( x2 ), 1g, 500mg, 200mg( x2 ), 100mg, 50mg, 20mg( x2 ), 10mg

So you have everything necessary for a solid testing procedure. It seems to me that you should be using one of those weights every time you weigh a powder charge on both scales to determine if either of them has drifted since the last measurement. That way, you could tell what, if any drift, each scale showed and, if the drift is correlated, it might indicate that the drift is caused by something external to the scales or, if uncorrelated, internal to one or the other.

My scale drives me crazy sometimes in that it will be fine for hours and the suddenly drift .04 grains then go right back where it was. It can also show some sensitivity to where on the scale pan I put the powder pan. Maybe there are ways to stop this from happening but I depend on the check weights to tell me when it has happened.

Thanks for all of your hard work on this. It has been very helpful.

 

[CoverDog]

tonyR....In the third paragraph under Scale Calibrates Quickly it reads:

I set the calibration weight on the scale between every one of the 30 loads I weighed. Only once did it vary from the 308.64 grain reading when it moved up to 308.66 grains.

This was not done each time on the Pact scale since it could be off by .09 grain and still show it was "right on" since it only reads to 1/10th of a grain.

 

[TonyR]

tonyR....In the third paragraph under Scale Calibrates Quickly it reads:

I set the calibration weight on the scale between every one of the 30 loads I weighed. Only once did it vary from the 308.64 grain reading when it moved up to 308.66 grains.

This was not done each time on the Pact scale since it could be off by .09 grain and still show it was "right on" since it only reads to 1/10th of a grain.

Sounds good.