The Great Debate — Weight vs. Volume in Powder Dispensing
When we first ran this story a while back, it spurred a hot debate, with strong opinions on both sides of the issue. Some guys argued vehemently that volumetric powder dispensing was best — citing the experience of short-range benchresters, most of whom still throw their charges. Others say weighing your charges is best, so long as you have a very precise, and very repeatable scale. We know some of the top 1000-yard shooters weigh their charges to the kernel.
Most competitive long-range shooters weigh powder charges for their handloads. Some even use ultra-precise magnetic force restoration scales to load to single-kernel tolerances. But is weight-based measuring always the best way to fill a case with powder? Another option is volumetric charging. This method fills a precisely-sized cavity with powder and then dumps the charge into the case. A Harrell’s rotary powder measure works this way, as does the sliding powder filler on a Dillon progressive press.
For long-range applications, most people believe that precise weighing of powder charges is the best way to achieve optimal accuracy and low ES/SD. However, those short-range Benchrest guys do pretty darn well with their thrown charges, at least at 100 and 200 yards.
Our friend Dennis Santiago recently observed something that made him scratch his head and wonder about weighing charges. His AR-15 match rifle shot better with volumetric (cavity-measured) charges than with weighed charges dispensed by an RCBS ChargeMaster. Here’s what he reports:
Cavity vs. Dribble (Dennis Santiago Report)
I had the chance to compare nominally identical ammunition loaded two ways. These were all .223 Remington match loads using 77gr Sierra Match Kings over 23.4 grains of Hodgdon Varget. Same gun. However I loaded some ammo with charges dispensed with a Lee cavity-style powder measure while other rounds were loaded with powder weighed/dispensed by an RCBS Chargemaster. The cavity-drop ammo (with powder dropped from the Lee unit) was consistently better than the weighed-charge ammo. I have no idea why…
So, ladies and gentlemen — what do you think? Why did Mr. Santiago’s volumetrically-charged ammo shoot better than ammo filled with weighed charges? What’s your theory? Gary Eliseo suspects that Dennis’s Chargemaster might have been drifting. What do you think? Post your theories in the comments area below.
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Tags: Charge Weight, Chargemaster, Dennis Santiago, Highpower, Powder Measure, RCBS, Reloading, Volumetric
I use an RCBS Chargemaster and have found that there is variance in the weight of the charges dispensed. It depends on the weight of the charge and the shape of the powder. I can dispense 39.8 grains of H4350 and the results are mostly within .1 grain. But if I change to 40.1 grains, the charges can vary much more. It all has to do with how the trickle works at the end of the charge and if the powder “clumps” in the end of the dispenser tube. You can find several articles on how to tweak the Chargemaster speeds depending on the weight range selected. Some put a piece of a straw in the end of the tube to prevent clumping. I use the Chargemaster to dispense about .3 grains less than what I want then use a very accurate scale to trickle in the last few kernels to get a precise and consistent weight. Takes a little longer but it works.
I’ve had a similar experience to Mr. Santiago: In a 223wssm varmint rifle, my charges dropped from a Harrel measure consistently group slightly better than the ones weighed on Chargemaster. This is with H414 powder.
I’ve tested it several times over the last few years.
1. All powder weighing is by weight. Note the graduated elements on both the Lee and Harrel measures. The “volume” in the cavities is to reach an indicated charge weight.
2. You are seeing different scales yielding different weights. The issue is the repeatability in generating the target charge weight.
3. All other things being controlled, including allowing any electric scale stabilize and turning off all other power devices on the same circuit (seriously), take 10 charges from scale A and 10 from scale B. Measure them on a third scale – one that is certified for very high repeatability and just calibrated to a certified test weight. Let us know what you find – and, of course, identify all three scales.
4. IMO, the on-target differences are a function of the differences in charge weights. Test to compare the repeatability of the charge weight. The more consistently repeatable will yield the superior on-target results.
Precision Shooting Magazine published an article a number of years ago that came to the same conclusion. Volumetrically charged rounds were more accurate than weighed charged rounds. I recall the article was well done scientifically but I was puzzled with the results. I no longer have the article (early to mid 1990 would be my guess). Perhaps someone can review their collection of old Precision Shooting magazines and share the discussion. Shame they are no longer published. I would be interested in a CD or electronic access to the info.
For a reason not known to me, variation in velocity is less critical at short range.
So your super accurate 100yd load with 30f/s ES will be less than impressive at 1000yds, with lots of vertical.
you post sentence “However, those short-range Benchrest guys do pretty darn well with their thrown charges, at least at 100 and 200 yards…”
Well, they also use flatbase bullets. Now try to shoot that same bullet at a 1000yds and we all know that their target will be much less stellar.
There are horses for the courses. Short range BR can volume drop their loads but long range [shooters] will very carefully weight their loads because single digit SD is what you are looking for to minimize your vertical spread at that distance.
I vote with Gary Eliseo.
The RCBS Chargemaster uses a low-end scale based on strain gauge technology. It does not respond accurately to small amounts of powder added to the pan. This is not to say the scale is unusable, but certain precautions are required to wring optimal accuracy out the scale.
Plug the scale into a line conditioner to reduce noise in the power supplied to the scale. This will reduce drift.
Calibrate the scale to begin each re-loading session and use a check weight to confirm that the scale is holding its calibration during the course of the reloading session. Ideally the check weight should be close to the powder weights being measured. Confirm calibration every 10 to 20 charges dispensed. Re-calibrate as needed.
Or, buy a quality analytical balance using a magnetic force restoration load cell ($800 to $1,000).
I forgot to add on more important consideration for the RCBS Chargemaster … after powder dispensing is complete, reweigh the powder charge by removing the pan from the scale, allowing the scale to re-zero, and then reweighing the charge. Re-weighing gives the correct powder weight.
In my opinion the RCBS charge master is not a good scale for accuracy. If we look at the basics:
.1 readability
+/- .1 of accuracy.
In terms of a charge of 24.0 of varget
We can read down to .1 so the charge can be 24.01 to 24.09
The scale is accurate to +/- .1 so the actual charge can be 23.9 to 24.1
Now if you look at the potential extreme spread: you can be ~23.9 to 24.19 or an ES of ~.29 in weight or 1.25% of the total charge or in terms of a 77SMK think the bullet variance being ~1 grain.
For the record I recently bought an MFR scale with an after market trickler. So far as far as reloading equipment goes it’s the best $1450 I’ve spent; I get dropped charges almost as fast as I can pour them into cases and prep my second pan of powder. I haven’t chrono’d the rounds yet, but between myself and another shooter we had no elevation problems at 1000 yards when we switched to this ammo. Other shooters using the scale trickler combo report mid to high single digit ES on bullets going 2900 to 3050.
I have no doubt the ChargeMaster is drifting. I use mine only to dispense a close charge. I then weigh using an AND Scientific scale.
Case capacity is likely closer with the thrown rather than the weighted charges. Could be a more important factor.
all over again this nonsence limited test…
harrell’s = top, charge master = low,
shooting groups = probability,
shooting 60 shots at match = consistence.
check with 3000$+ scale what are REAL charges at harrell’s and rcbs chargemaster.
everything else is BULLSHIT!
Most of this info is dead-on. One thing that’s
often overlooked is how the powder is dispensed into the cartridge. McPherson and Zediker agree that the benefit BR guys see with throwing charges is consistent way they dispense/swirl the load into the brass. Another factor is that a powder measured by volume is less affected by humidity changes than one that is weighed, owing to the fact that powder can weigh more if it absorbs moisture. The other issue is that us LD guys use long extrude grains which don’t meter as well in a powder thrower. What i do for my 1,000 plus accuracy loads is carefully weigh each charge using well calibrated scale that i know is accurate and then swirl each charge into the powder funnel which duplicates the effect of throwing the charge and allows for more uniformity beteeen charges over just dumping the powder down the tube.
One thing that’s
often overlooked is how the powder is dispensed into the cartridge. McPherson and Zediker agree that the benefit BR guys see with throwing charges is consistent way they dispense/swirl the load into the brass. Another factor is that a powder measured by volume is less affected by humidity changes than one that is weighed, owing to the fact that powder can weigh more if it absorbs moisture. The other issue is that us LD guys use long extrude grains which don’t meter as well in a powder thrower. What i do for my 1,000 plus accuracy loads is carefully weigh each charge using well calibrated scale that i know is accurate and then swirl each charge into the powder funnel which duplicates the effect of throwing the charge and allows for more uniformity between charges over just dumping the powder down the tube.
My thoughts are moisture content in the air I use a Harrel’s and Dillion both measure the powder well,Humidity affects the weigh changing from early morning to mid day/evening. Powder is so dry it sucks moisture and can very,measured it does not matter they will be closer over all humidity ranges .Yes ,maybe a small amount but , if your off two tenths from what you want, because setting the powder measurer is by weight to start with, they still are all the same through measured powder.