How to improve the accuracy of a powder thrower

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
Tried something today that i thought should be shared:

Have an old RCBS powder thrower, inherited from a family member, which on a good day is accurate to maybe 1 gn. Not nearly good enough for accuracy loads. And not safe either unless you are miles away from the pressure limit.

[I do realize that a Neil Jones or similar BR thrower will be far far more accurate, but it is pricy.]

Read somewhere that some folks prevent compressed loads by using an ultrasonic toothbrush to settle the powder. Tried it, and worked quite well.

From this got the idea to mount the ultrasonic tooth brush against the powder thrower reservoir. Used a rubber elastic band to attach it. It rattles the entire device pretty effectively.

Then did some tests: Found that the cheap low quality RCBS powder thrower could now achieve 3x to 4x better standard deviation than before, using Hodgedon Benchmark powder. It has the bent circular plate in the reservoir with the two holes for more even “head” (powder column height above the measuring chamber). This does seem to help a bit, but still not really good enough.

I realize this is a pretty obvious idea, so i am sure others have tried it before. Would be curious to hear if you got the same or similar result. Any modifications or improvements?

I used to throw the charges about 2 grain below the desired weight and would then trickle up to the final value (FX120 plus V1 auto trickler). Now i can set it 0.5 gn below spec, and that speeds up the process.

So for obvious reasons, I still weigh the charges to be on the safe side, but it is much quicker now to trickle it up to the correct weight.

BTW: Would not recommend charges be thrown anywhere close to a max charge. No matter how good you think your powder thrower is. As always, your mileage might vary.

Be safe!
 
Last edited:

Dstoenner

Private
Minuteman
Dec 10, 2018
60
24
12
Another trick I use with my RCBS Uniflow with the small drum cavity is to divide my charge on my smaller cartridges so I do 2 dumps for a given powder charge and for my 308/30-06 I do 3. This then tends to nuetrilize the +/- variation a little. So I have fewer dump backs. If I am over a few .1's I just pinch some powder and put it back in the column.

And I weigh every charge, even for powders like 8208. I have seen the .3 low maybe once in 50 cases but that could be bad news on the target.

David
 

chevy_man

Gunny Sergeant
Belligerents
Minuteman
Jan 25, 2019
558
372
69
I use a Redding thrower with ball powders, and I've found its damn near perfect.
I use a gempro scale to verify. I get more variation in the Hornady auto measure with extruded powders than I do with the thrower with ball.


That said, any thrower is going to suck with extruded powders. May well be faster to use a Lee scoop set and trickle up.
 

Steel head

Stylish Ninja
Belligerents
Aug 3, 2014
3,979
3,249
219
Washington
With friendly ball powders(WST and W748) and consistent technique I’ve found both my Hornandy and RCBS powder throwers to be as or more accurate as my Hornandy electronic powder measure.
 

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
Good info. Have also had pretty good results with ball and flake powders. Extruded powders like H4350 were really bad, up to a grain in variation. Would guess 0.3 to 0.4 grain SD.

The toothbrush trick seems to improve that situation quite a bit. Would be curious what results others get when they try this.

Just remember powder and primer residue can be toxic, so wash the device thoroughly with soap and water before re-using for original purpose, and replace the brush head with a new one. [Then again: Perhaps best not to re-use again! 😊]
 
Last edited:

Smallcalshooter

Private
Minuteman
Jan 19, 2019
10
2
6
I used the uniflow for years not vary consistent throws. Lots of cut off. Tried the lee perfect powder measure for 25 bucks. Much better. No cut off at all. Most times l have to trickle 4 kernels +or-
 

sinister

Gunny Sergeant
Belligerents
Apr 16, 2002
1,715
152
169
College Station, Texas
You can also try using plain automobile Turtle Wax inside the drum, measuring chamber, internal funnel, and powder tube to cut some of the friction between stick powder kernels and the powder measure body. Helps to keep everything flowing without drag (which the toothbrush also helps with for settling).
 

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
I used the uniflow for years not vary consistent throws. Lots of cut off. Tried the lee perfect powder measure for 25 bucks. Much better. No cut off at all. Most times l have to trickle 4 kernels +or-
Good to know! At $25 it is worth a shot!

The RCBS Uniflow has been a little frustrating.... not at all uni-form...
 

slodsm

Private
Belligerents
Jun 1, 2009
109
96
34
41
Fort Worth Texas
www.google.com
I use a lee el cheapo powder throw and depending on the powder, it’s ridiculously accurate. When loading precision loads with varget I throw and weigh 10 and then just check every 25 and it’s dead on.

Other powder like 4064 it won’t meter as perfectly and I set it to be .2 low and sometimes it’s dead on, sometimes .2-.4 low and I just trickle in.

Takes a little longer but I get very consistent loads.
 

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
I use a lee el cheapo powder throw and depending on the powder, it’s ridiculously accurate. When loading precision loads with varget I throw and weigh 10 and then just check every 25 and it’s dead on.

Other powder like 4064 it won’t meter as perfectly and I set it to be .2 low and sometimes it’s dead on, sometimes .2-.4 low and I just trickle in.

Takes a little longer but I get very consistent loads.
Have ordered the Lee powder measure from Midway, very reasonable price. Looking forward to using something that works better....
 
Last edited:

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
Have ordered the Lee powder measure from Midway, very reasonable price. Looking forward to using something that works better....
OK, Lee powder measure arrived last week, and had it set up in less than 10 minutes.

Used it with H4350 to charge 40 cases. Picked H4350 as it is a course large grain extruded powder which the RCBS Uniflow does not handle well. Typical ES is 1.4 grains, SD around 0.45 grains. Which is unacceptable.

Results for the Lee device were amazingly good: Standard Deviation (SD) was around 0.15 grains, ES was 0.35 grains, about 4x better than the RCBS, which will be in the trash tomorrow. Now i know why a friend gave it to me FOR FREE!

The Lee is accurate enough in fact that if you throw the charge and then weigh each, you can batch the rounds into two groups, each 0.1 grains apart, and throw back the odd charge that is out by more than 0.2 grains, you could very rapidly have 50 of each weight ready for bullet seating. Should be good enough for practice ammo suitable for 300 yards target practice at steel targets, i think. Very fast!

I would highly recommend the Lee powder measure. Cost was less than $30, which is a bargain. Yes it looks like a cheap made-in-China plastic device when you unpack it, and it is smaller than you expect it to be, but man it WORKS like a champ!

@slodsm: Thanks for the tip!
 
Last edited:
  • Like
Reactions: Tx_Aggie

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
I use a lee el cheapo powder throw and depending on the powder, it’s ridiculously accurate. When loading precision loads with varget I throw and weigh 10 and then just check every 25 and it’s dead on.

Other powder like 4064 it won’t meter as perfectly and I set it to be .2 low and sometimes it’s dead on, sometimes .2-.4 low and I just trickle in.

Takes a little longer but I get very consistent loads.
My next experiment is to attach the Phillips vibratory tooth cleaning device to the Lee and see if it gets even more accurate...

Update: The toothbrush did not make much of a difference here. As long as you move the lever slowly and give it 2-3 seconds to fill, it is quite accurate, if you get impatient you lose accuracy.

Repeated the experiment and got an SD of 0.2 gn. Still good enough. But you might want to batch the rounds into three groups, throw back the rest.
 
Last edited:

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
I use a second hand Phillips SoniCare, and elastic bands to attach it to the reservoir, also i cut the brush section off so no grand child will stick it in his mouth one day.... It seems to create a pretty high frequency buzz. Mounted it head up, but i doubt that will matter much.

If you weigh each throw on a cheap 0.1 grain scale and have three rows of prepped brass with three funnels lined up, say 40.5, 40.6 and 40.7 gn (and throw back the rest) you can load practice ammo really fast. As long as you are in the middle of a wide node, and you got positive compensation on your side, you might be surprised just how well such ammo works out to 400 yards.

If you use a progressive press, just sort the loaded rounds into three groups based on weight as they come off the press. No trickling required, which is the slow step.
 
Last edited: