Bad RCBS Uniflow Powder Measure?

J

jski

New member
This occurred AFTER I disassembled the entire measure and cleaned it with alcohol:

I got some .45 Special brass from Starline for my .45 Colt S&W Mountain Gun. I decided on RamShot True Blue powder with my 255 gr., GC, hard cast bullets.

7 gr. of True Blue seemed like a good load.

Used my Gem Pro 250 to weigh the charges thrown by the RCBS measure. Got consistent 6.9-7.0 throws on consecutive throws and tightened the measure screw. I reloaded 100 rounds and re-measured.

I got 9.4 gr. INCREDIBLE!

Guess I need to order a bullet puller. Probably shouldn't order an RCBS puller.

Any thoughts?
 
You should have checked your powder weight every 5-10 rounds on a scale to make sure the powder drop was set correctly. Also, are you using a baffle in the RCBS powder drop? This helps a LOT with lighter charges of powder.
 
"5-10 rounds..." That's a bit excessive. Clearly something went wrong on the initial weighing or tightening of the screw. The Uniflow is an exceptional thrower and TrueBlue should not need a baffle. We've all been there. You're positive of a charge - 30 rounds in you find out it was wrong. Doesn't happen often, but it can happen. Impossible to determine exactly what happened. But, once they are set, they should be good for 50 to 100 rounds without issue.
 
I have a Uniflow.

And this phenomenon is why I stopped cleaning it. I have a similar story to yours; except it's over thirty years old.

Here's what I think is happening (someone smarter than me may have a better answer) . . .

The first time you use it after it's thoroughly cleaned, with every throw, some propellant is accumulating on the inside walls below the throw (due to friction, static electricity, moisture, capillary action :p, who knows?). Anyway, you set it while it's accumulating propellant; soon after, the walls "saturate" and your throws begin depositing the entire amount into your case - which is far more than you originally weighed - because it is no longer depositing some inside the bottom walls of the hopper.

That's my theory. I have repeated the phenomenon. Takes about twenty or thirty throws before it "saturates" and starts giving the case all the propellant.

I don't clean mine any more. Problem solved.
 
What Nick C S said. I cleaned mine and it did the same thing. Something else I do to keep it consistent is to give the handle three knocks each time before raising and lowering so that the powder settles the same each time. If you fill it to the top it will give bigger drops than when it's getting low. I never fill it more than about 1/3 full and always three knocks.
 
Spherical powder measures like water so no tapping or other stick powder techniques should be needed and there is not a lot to break in a powder throw. It is just a cavity in a rotating cylinder. The cavity has a plug that screws in and out to change the volume. The cylinder rotates between fill and spill

Sounds like a static problem. Try a wipe down with an antistatic cloth and spritzing some powdered graphite down into the cylinder to see if it helps. Check the cavity for dead bugs too. I had my Hornady give me a fit one day. When I dis assembled it to clean it I discovered a spider had crawled into the cavity and died
 
I have an old one. Its very inconsistent vis a vie an electronic scale.

When I am forced to use it, I just adjust low, put it on the Lyman electronic with the built on trickler and bring it up.

Stand alone I would weigh each round into a pan.

I would never trust it with stick powder without a cross check.

I don't do a lot of ball so less sure on that end.

Pistol powders when I did those a lot I still weighed each charge.

I sure would not trust it with 9mm.
 
If you used isopropyl alcohol I hope you used some air to blow it dry or let it set for a while before using the powder measure, isopropyl alcohol contains water and it can get trapped and not dry out as fast as the alcohol does. This can cause the powder to be trapped and clog the measure.

Also I recommend getting some powdered graphite and right after you clean and dry pour the graphite into the powder measure and shake it a little then run the graphite through the powder measure a couple of times tapping the measure as you run it through, this will coat and lube the measure and stops a lot of issues like what you described.
 
Northof50, when I mentioned "every 5-10 rounds", I should have been more clear.
Just check the weight every 5-10 rounds till the powder measure is calibrated and set properly. Then, load away, with the occasional check to make sure the weight is correct.
 
Rifletom- Yep. After I typed, I thought there had to be more to it. It's funny, I've had similar things happen [as the OP describes]. I'm at the point in which I'll check 4 or 5 times before I start [progressive reloading]. But, after I'm sure - I have to admit- I'm done checking until the end of my session [about 200 rounds]. I'll then check again. If I'm going to continue with reloading the same load the next day, I'll check it again the next day. But, the Uniflow [mine has the micrometer adjustment] is brilliant. Once its dial in [correctly] it's there until it's adjusted.
 
I went with the Lyman inertia bullet puller. Don't know if the RCBS puller allows you to use your case holders like the Lyman does?
 
I believe all these inertia bullet pullers work the same way. I have the RCBS one, same as Lyman's. Honady also makes their Cam Lock bullet puller. Way easier.
 
I also question the wisdom of using isopropyl alcohol on any powder measure. What you want to use is powdered graphite that is easily found at any automotive supply store to keep it moving freely.

Don
 
Bad RCBS Uniflow Powder Measure?
Click to expand...

I have at least 5 Uniflow powder measures, I have one each for each Piggy Back attachments, another for the Pro-2000 and then I have a few that comes in boxes with two powder drums, I would not think of using one without running a few hoppers of powder through them. After that I apply the leaver policy I leaver with the coating of dust etc.

And there is another discipline, I sort components by weight; when finished I know the weight of the case, bullet and powder with primer, if the weight is off it has to be the powder. In reloading the saddest words of verse or pen has got to be: "It musta-been a double charge".

F. Guffey
 
Northof50 said:
"5-10 rounds..." That's a bit excessive.
Click to expand...

.....it depends.

The OP on another gun forum stated that he has experienced the same phenomenon at other times with other calibers. Thus, one would think you would do a powder check more regularly than only after you have reloaded your entire batch, until you have figured out the problem. The Uniflo is a simple machine, incapable of changing it's settings on it's own. Either there is a powder problem or a user problem.
 
I have an older Uniflow and have had zero problems. Actually, quite impressed with it's consistency. I mostly load faster burning pistol powders( Bullseye, Titegroup, HP-38,etc). My only issue is powder sticking to the hopper due to static.
 
I have an older Uniflow and have had zero problems. Actually, quite impressed with it's consistency. I mostly load faster burning pistol powders( Bullseye, Titegroup, HP-38,etc). My only issue is powder sticking to the hopper due to static.
Click to expand...

Wipe the inside of the hopper with one of those dryer sheets that the wife uses when doing the laundry. Problem solved.

Don
 
where I live we can have very wide swings of humidity and my reloading room was a shed for a while..... very dry days had a lot of static where I could see the powder cling to the top of the hopper as I filled it....grrr

Initial in the house (temp controlled by a AC unit) reloading room had carpet... humidity swings were not as wide but deep winter or hot summer with AC on a lot...I was getting a lot of static

Removed carpet
Put in a WalMart cheap Humidifier set to 44%
Changed out all Ballast Fluorescent fixtures to the very nice and bright LED 4 footers

Balance beam is no longer nutzso... same with digital scale, powder drops now don't accumulate static kling

I have a wood working shop with a large vacuum system that must be grounded to each tool and the ground circuit of my electrical system.... very simple to just attach a small gage copper wire to the reloading tools to ground away any static

basic reason I mention all this is... initial wipe with used dryer sheet is a very temporary fix in any low humidity environment.... if you shake the hopper a bit and see grains jumping up and sticking to the sides....then it is good bet the powder should throw a LOW charge most of the time and then whammo all the built up powder in the cylinder with dissipated static will throw a heavy charge.......dissipated cuz you touched it... or banged it

IMO there are only a few inaccuracy modes for powder droppers
Dirty oily
Static
Worn out...loose
 
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