Gempro 250 / 500
- Thread starter JDY
- Start date
I use a 250 and have loaded up to 98+ grains of h1000 with no issues. At first I would randomly verify charge weights with ole trusty beam scale 10-10. No issues, of course like the previous post theres other higher end scales out there.
Ask your reloading buddies maybe some might have either scales you could borrow for a test drive per to say.
Ask your reloading buddies maybe some might have either scales you could borrow for a test drive per to say.
If I recall right, such scales tend to be more accurate when they approach their maximum capacity, so if you're only using it to measure powder, then the 250 has the lesser capacity.
Incidentally, I've found that for my favourite loads, it simple to make a standard weight for each load to check the scale with. A I work with .308 capacity cases a lot, I've found that I can trim some old 50 grain soft point bullets for each & scratch the weight on the body.
Incidentally, I've found that for my favourite loads, it simple to make a standard weight for each load to check the scale with. A I work with .308 capacity cases a lot, I've found that I can trim some old 50 grain soft point bullets for each & scratch the weight on the body.
I have the Gempro 250 and it's fine for measuring static weight. I bought it when I did not have the budget for the A & D magnetic force restoration scale that I later bought. They both weigh consistently to 0.02 gr but, and its a big but, the Gempro does not respond well to trickling. The solution is to take the trickled load off the scale, allow the scale to settle, then put it back, sometimes it weighs the same, sometimes not but generally it's an easy fix to take a kernel or two off or add with tweezers. it is a good value scale in my opinion, however, the A&D responds far better to trickling and is a huge time saver. Others on this forum have reported a not so good experience with the Gempro, but as I say, in my view, the one I got was good value and filled the need for the available budget at that time.
Martin
Martin
.02 grain accuracy will make a difference at the range? Gee, why fool around? You should measure powder by counting the number of granules. :
Maybe also make sure they are all stacked in the case exactly the same?
Maybe also make sure they are all stacked in the case exactly the same?
rap36case
Working up loads for new Shilen 308win
I'm an analytical chemist. In the lab, I use Sartorius or Mettler. I always use standard weights to verify operation. The same practice can be used with GemPro 250. I use a 41.52grn standard made from a small vial and verified on an analytical balance. The precision is excellent after warm up period. The bottom line is SDs for groups average 5fps with loads weighed on the GemPro 250.
GemPro 250 at the price point for sure. Accurate to +/- 0.02gr. Make yourself a little check weight out of a screw or nail and file it down until it matches your target load weight. Then you can periodically weigh it to make sure that your scale hasn't drifted and that your loads are consistent from session to session.
And as mentioned above it's not great for trickling charges, but it's accurate for a static weight. If you've got powder that is consistent in kernel size you can do the math to figure out how many kernels per 0.1 gr and just throw once then add in the necessary number of kernels to hit target weight. Varget is is easy. 0.02 per kernel, 5 per 0.1g, at 10 kernels you need to skip one since they run just a tiny bit heavy. Super fast to load precision charges within 0.02gr. Looks like this....
And as mentioned above it's not great for trickling charges, but it's accurate for a static weight. If you've got powder that is consistent in kernel size you can do the math to figure out how many kernels per 0.1 gr and just throw once then add in the necessary number of kernels to hit target weight. Varget is is easy. 0.02 per kernel, 5 per 0.1g, at 10 kernels you need to skip one since they run just a tiny bit heavy. Super fast to load precision charges within 0.02gr. Looks like this....
When I started out I checked it dozens and dozens of times at different intervals. It works accurately, within the +/- 0.02gr capabilities of the scale. If I'm feeling OCD I check every once in a while.
Remember, one kernel is only 1 fps.
rap36case
Working up loads for new Shilen 308win
If you want to do a formal test of accuracy and precision, then you need traceable weights. I would measure at least 3 replicates, removing the weight each time re-zero and the re-measure. This will give you the repeatability. Then, do the same set of measurements on a different day with a different temperature and humidity (i.e. humidifier in the room and set the temperature lower or higher). If you get the same SD for each traceable weight, then you have robust reproducibility.
Finally, use a single grain for triplicate measurements, and repeat with more single grains. This will give you an accurate idea of grain mass and variation. I really doubt that extruded pieces are exactly 0.02grains in any powder.
Bottom line, just use a stable weight of metal such as gold or other non-tarnishing mass that weighs close to your target load mass. Verify with a traceable weight. Weigh your loads as accurately as you can AFTER you adjust the final mass of powder. Take them to the range and measure muzzle velocity with an accurate meter ( like the MagnetoSpeed chronograph). You will find your velocities vary only SD = 5fps for 5 to 10 shots. If you have worked up your load with a "sweet spot" node, then the 5fps will not effect POI.
Marksmanship accounts for more variation than most people want to admit (me included). Check out Owen's books found on AccurateShooter library.
Finally, use a single grain for triplicate measurements, and repeat with more single grains. This will give you an accurate idea of grain mass and variation. I really doubt that extruded pieces are exactly 0.02grains in any powder.
Bottom line, just use a stable weight of metal such as gold or other non-tarnishing mass that weighs close to your target load mass. Verify with a traceable weight. Weigh your loads as accurately as you can AFTER you adjust the final mass of powder. Take them to the range and measure muzzle velocity with an accurate meter ( like the MagnetoSpeed chronograph). You will find your velocities vary only SD = 5fps for 5 to 10 shots. If you have worked up your load with a "sweet spot" node, then the 5fps will not effect POI.
Marksmanship accounts for more variation than most people want to admit (me included). Check out Owen's books found on AccurateShooter library.
My goodness, talk about overkill.
My check weight works, it weighs the same every loading session. The empty powder pan also serves as a check weight (and gives you constant feedback by looking at the negative number on the scale when you lift the pan). Varget works for this technique. You're overlooking the fact that minute variations in kernel size get washed away and moved toward the average as soon as you toss in multiple kernels. As I said previously, I've double checked a LOT of these charges with a second weighing. To the point where I'm confident that they are accurate to +/- 0.02g (the scale's stated capabilities) the first time and I don't need to weigh them again and again.
Your post also presumes that powder weighing is a guarantee that you'd get a good velocity SD, or that you can't get a good SD if you're not weighing powder and triple checking every charge. Neither is true, some charges loaded to kernel accuracy can still give you a SD of 10-15 and on the flip side there are plenty of people using just a Chargemaster getting an SD of 5. Node selection, component selection and brass prep are bigger factors than powder weighing in my experience.
Finally, look at what calibers the OP said he is loading. He's not shooting BR, so we can perhaps steer our advice accordingly.
rap36case
Working up loads for new Shilen 308win
LOL. I am not directing anybody to do their hobby a different way. I am reporting what I do and don't care if someone does it differently, as I am retired. I was an analytical chemist, lab and quality manager, so my habits are a bit different. My muzzel velocities and SDs improved after getting a GEM Pro 250, and I attribute most of the improvement to the increased sensitivity. What ever works and satisfies the end user is fine. NIST traceable standards give you some additional assurance, if you want to spend more money.
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