How Accurate Does a Powder Measure Have to Be?

Exact charge weights are sometimes not needed for excellent accuracy or precision. Best example is what military teams learned with their 30 caliber semiautomatic service rifles.

Best accuracy in M14NM and 7.62 converted M1 Garands with best lots of M118 ammo was about 2.3 MOA at 600 yards. Charge weights of IMR4895 had spreads of 3/10ths grain. The 173 grain FMJBT match bullets came from 3 or 4 different sets of dies.

Rebulleting that ammo with Sierra 180 grain HPMKs produced ammo that tested about .67 MOA at 600; powder charge weight spreads were not changed.
 
I will relate it this way from my own personal experience.

If I were to load 20 cases at say 10.0gr and hand weigh each one to assure exactness and then loaded 5 at 10.2 and 5 at 9.8 and then randomly sprinkled those to into the other 20 and then shot them all. I would never be able to tell anyone which 5 were over and which 5 were under.

Knowing this, I still over weigh check my loads.
 
Technique has a lot to do with the consistency of any powder measure. If you are moving a tray of 25 or 50 pieces under the measure spout and repeatedly dumping charges from start to finish, you will almost surely have more consistency across 50 pieces than you will if you dispense one charge, dump it in to a pan, put it on the scale, remove and dump it, then dispense another charge from the measure and weigh that one.

Furthermore, if you haven’t REALLY shaken out your scale to be dead sure certain that what you read is what you actually have, you might well be questioning the wrong tool.

I will say that Accurate#7 is a pleasure through most measures. If you told me that those were your results with Unique, I’d say you are fine. AA#7, I would expect better from my Lyman 55 and a quality beam scale that only counts on gravity and not a cheap junk chinese load cell, a wacky current affecting how it’s reading, a curious drifting zero and all the other nonsense associated with digital scales.

Full disclosure: digital scales suck. Some will disagree with that opinion. I mean no personal offense, but I’ll stick to my position that digital scales suck.
 
I still over weigh check my loads.
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because there is so many things in this game we cannot control we control what we can. I tr not to be overly anal these days. But there are few things like distance from lands, primer seating depth both of which I think are crucial. I develop my loads to have a couple of tenths leeway but out of habit I still like to get it as consistent as possible. But I do get what you are saying, if it is on a good node it can be off a tad. The exception being if that load is pushing the pressure beyond what is smart. I try to load to the middle node myself, but that is just me. Overall though I think like you do for the most part


edit - On the manual vs digital I have used both and gotten good results from both. I use a medium end digital for speed but still have my Lyman and RCBs scales on the bench. Just my preference
 
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“It's Accurate No. 7 in a Hornady Lock-n-Load progressive. Seems to be working! I filled 77 old Starline cases.”

This measure was made before they put baffles in them. I don't know if they're helpful or not.




On my LNL AP Powder measure with a baffle and pistol rotor the charge is whatever I set it to. Bullseye, HS-6, 231, 296 etc the same. With Unique and no baffle no more than .1 grain off. Have to keep the measure half full when using Unique though.
You might want to try a baffle if the couple tenths of a grain is bothering you but unless you are loading at max charge don’t think it will make that much of a difference.
 
Sevens said "Technique has a lot to do with the consistency of any powder measure. "

I completely agree with that and the described technique of continuing a serieswithout interruption. Yesterday I loaded 30 rounds of 6.5 Creedmoor with H4350 and I checked every charge for the hell of it on my RCBS digital scale. I pulled 2 off line because I felt the powder granules had bridged or cut since the drop was not as smooth as the others. These weighed 40.2gr; the other 28 weighed 40.1gr.
 
Sevens said:
Technique has a lot to do with the consistency of any powder measure. If you are moving a tray of 25 or 50 pieces under the measure spout and repeatedly dumping charges from start to finish, you will almost surely have more consistency across 50 pieces than you will if you dispense one charge, dump it in to a pan, put it on the scale, remove and dump it, then dispense another charge from the measure and weigh that one.
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^^^I too have to wholeheartedly agree with this. What folks need to remember tho, is a powder measure/thrower measures by volume, not by weight. You adjust it to throw a volume close to the weight you want. It is basically a mechanical dipper. Just like using dippers, one need to be consistent with how they allow the dipper to be filled. Using a powder measure off press generally is more "accurate"(yeah, since I'm not a grammar Nazi, I'll use accurate) that using one attached to a press where there is more random movement. I always use the "double knock" technique where I use enough pressure on the handle to "tap" on the downstroke and the upstroke. This seems to make the powder settle more evenly in the measuring cup and the hopper, especially with larger flake and bulky powders. For general shooting and plinking, the average reputable brand powder dispenser/measure is good enough. For only the most accurate rounds does one really need to weigh each charge. Just weigh every 10-20 drops to make sure the powder is still settling evenly and go from there. Some powders shoot more accurately when measured by volume than by weight. FME, Unique is one of these.
 
Regarding digital scales, I have a Lyman. I noticed it was moving around for no reason. I would leave it sitting, and suddenly a couple of tenths of a grain would appear or disappear.

I was using a fresh 9-volt battery, figuring batteries give the most CONSISTENT (not accurate) voltage, but I switched to AC, and oddly, I have not had problems since.
 
I have a surge protector into which I plug my RCBS digital scale.

"SL Weber Power Master" Surge/Noise protector Model PM IN
On board is a window: Green=OK Black= Replace

I also have a surge protector connected to my circuit breaker box. I'm in my home 21 years and I have 22 standard 65 watt floodlight on one (main) floor in my home and I have changed only 3 bulbs during that time. That doesn't count the same bulbs on my lower and bedroom floors, nor the outdoors lamps.

Surge protection may be the answer.
 
Are you going for Bench Rest Accuracy levels or just blasting ammo? If A) then each charge needs to be checked against a real accurate (IE not Harbor Freight) scale. If B) I've loaded thousands of rounds using scoops. As long as B isn't at the very top you are GTG> That said I have a pet load for 357 that features plated bullets, AA#9 powder, certian brass & primers and are loaded with a custom scoop. This general recipe is RBH accurate to a 2 liter bottle @ 200 yards 5 out of 6 with my gun.

So what are you REALLY after?
 
I want the gun to be able to hold 1" at 7 yards. On a good day, I can put most shots in 1.5" without a rest, so I want the gun to shhoot better than I do.
 
Test the firearm in a return to battery machine rest. Then your variables won't add to those of firearm and ammunition. I've seen 50 yard test groups shot from rebuilt M1911 45 ACP shooting Remington 185 gr. wadcutter ammo that all are under 1.5 inch. Pistol was held by a Broadway machine rest that's similar to the Ransom rest

Regarding (semiautomatic) pistol accuracy, I think the most important part is getting the barrel perfectly aligned with the sights axis after chambering each round.
 
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The range you posted looks good.

I just used my thrower for about 150 cartridges of 223 .m I wanted 22 gr and every time I checked thrown weight it was either 22, 22.1 or 21.9 gr. That was good to go for me.
If Im loading hunting rounds, usually 50 or less, I weigh each and get it right on my desired weight.
 
I'm sure everyone has eventually noticed different powders have different densities and sizes, esp the rod-type with the "short-cut" being a smaller version. I have a Bruno powder measure which I believe to be very well made, but accuracy in it as well as those I have from Redding and RCBS can be a challenge with the rod-type powders.

I noticed when trickling some heavier density powders may take 1-2 granules to get to 0.1gr while others take 2-4 times that amount. With bridging and cutting of the granules, variation can occur.

I was loading 25-06 this morning with RE22 which brought this to my attention, and I refelcted on how different it was from H4350 when I loaded my Creedmoor. I had one of those really rare occasions with H4350- it dropped 40.1 grains in 30 consecutive throws, much to my amazement.

Contrast that with 51.0 grains of RE22. I loaded only 37 rounds but I weighed every one because the first ten gave me a range of 50.7 to 51.4 grains. 60% were 51.0-51.2;
20% each were over 50.2 and under 51.0. I had 2 cuts during those 10; a 51.4 and 51.1. This is in a room with no drafts of significance.
 
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