Accuracy of RCBS Uniflow Powder Measure


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ezypikns
August 15, 2004, 05:59 PM
I've been trying to use my new Uniflow powder measure and I don't seem to be able to get consistent charges. I ran a pound of powder through it as was suggested. It will throw about 3 accurate charges, and then throw one off. I realize too that there's a learning curve in developing a 'feel' when you activate the charging arm on the powder measure. Incidentally I'm using Unique (flake) powder. What kind of accuracy range can I expest from a powder dispenser like this? To take it one step further, what is an acceptable variance in weight of powder for a .45 ACP cartridge?

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swifter
August 15, 2004, 06:32 PM
A lot o' guys complain about difficulty with Unique. I never had many problems with it in my Uniflo.Rather than trying to develop a "feel", you should try for consistency, making each move of the thrower arm as much like the previous as possible.

A baffle can be a great help, but spending a half hour a day throwing charges and weighing them to see how consistent you can get will work wonders in a week or two:rolleyes: .
Ya didn't expect to get good without practice, didja?:D

Tom

stans
August 15, 2004, 08:30 PM
The Uniflow with the large drum does tend to be a little inaccurate with large flake powders thrown at small volumes. I find Unique begins to meter uniformly at 6 grains, under that and it can become a nightmare. Bullseye is a smaller flake and works a little better. Spherical powders meter very well even at really small charge weights. I have heard, but have not yet tried it, that the drum with the small diameter charge hole is far more accurate with small charges of large flake pistol powders.

Jim Watson
August 15, 2004, 10:12 PM
"It will throw about 3 accurate charges, and then throw one off."

How far off?
No measure will deliver every charge right at the mark, there is bound to be a spread in powder measured by volume and checked by weight.

+/- a tenth of a grain for a 0.2 grain spread is very good performance you will likely see only with ball or small granulation extruded powder. A spread of 0.3 grain is about as good as I get with 700X which is a flake powder simlar to Unique, and sometimes worse. The ammo shoots, though.

Mal H
August 15, 2004, 11:36 PM
One thing I do when measuring flake powders like Unique is if there is a slight catch as the handle is rotated, I throw out that charge (dump it back in the hopper) and don't even bother weighing it to see if it's close. It usually means the edge of the measuring cavity is biting a flake and that charge is almost never close to a nominal charge (within +- .1 grain).

Peter M. Eick
August 16, 2004, 12:22 AM
I use a uniflow with a baffle and the small chamber adjustable add-on.

My normal load for 380auto is 4.0 grns of unique on a 90 grn JHP. With the uniflow fully loaded to the top and about 5 to 10 check charges dumped to get the settings right, I can throw charges very consistently from 3.9 to 4.0 grns nearly all day long. The keys are:

1) Baffle
2) Full load in the measure
3) Uniformity in operation of the handle
4) Getting enough powder run through the unit to kill the static charge
5) Concentration

I also agree that if you cut a flake or it studder it will be a bad charge. Toss it and try again.

candt
August 16, 2004, 12:40 AM
Mee too Mal H. I have the small cylinder and the baffle, and it throws Unique not very accurately. Not as good as AA powders anyway. It throws AA dead on every time. I love that stuff. I dont seem to have any luck with Unique or Clays.

Darkside
August 16, 2004, 02:20 AM
As said before the baffle will help as will a small cylinder for the uniflow. Work on consistant operation of the measure and you will get consistant power throughs. You will develope a rythum, one tap at the top of the stroke and two taps at the bottom or something like that but whatever you use BE CONSISTANT.

Wipe the measure with a Bounce anti stactic sheet really good, it is said to reduce the static. For what it's worth, I keep the sheet stored inside mine when I'm not using it.

Darkside

Kamicosmos
August 16, 2004, 03:20 PM
DarkSide said:

Wipe the measure with a Bounce anti stactic sheet really good, it is said to reduce the static. For what it's worth, I keep the sheet stored inside mine when I'm not using it.

Ditto, that static is a killer for awhile, powder will stick everywhere. Make sure you completly disassemble the thrower when you are changing powders to make sure you get it all out.

cracked butt
August 16, 2004, 10:28 PM
Not sure if RCBS provides a baffle with their Uniflows these days, but mine is about 15 years old and didn't come with one.
I gave up using it al long time ago until someone here mentioned getting a baffle. With a baffle, the powder measure works great, I can even throw Extruded powders very accurately with it with very few cut grains.


-Get a baffle.
-Spend an hour working on getting a good consistant throwing technique down.
-Keep the hopper at least 1/2 full, top it off as you go.
-When setting up the measure, throw 3 or 4 charges before weighing one- the first 1 or 2 will usually be off and you'll be chasing your tal trying to set it based on those.
-every time you top off the hopper, throw 2 or 3 shots of powder before going back to charging cases.

Getting accurate measurements with a Uniflow can be done, it just takes a little patience and persistance in establishing a good working technique.

Black Snowman
August 17, 2004, 12:43 AM
Something that hasn't been mentioned that is a help also is make sure it's mounted SOLIDLY. If it's bouncing around it's going to throw off the charges as well and can cause the powder to settle in the hopper.

Unless I'm using it for some other function I have my Uniflow mounted in my spare single stage press, a Lee Challenger. Very solid. Works well.

JA
August 17, 2004, 12:44 AM
Read a article several months back in the VHA magazine on powder measure charge weight consistancy using ball and stick rifle powders. Only the high $ benchrest measure beat it as the most consistant with the most powders.
The as issued measure was so-so but the tricked out measure and technique really impoved the consistancy. The additions were a baffel and a 3"-4" longer homemade handle. The technique was not to let the drum "knock" when the handle reached the end of it's travel either up or down. The vibration from the "knock" caused the powder to settle in the measuring chamber inconsistantly.

Ala Dan
August 17, 2004, 11:00 AM
Greeting's All-

I made a baffle out of an old washer, and inserted it at the base
of my large powder hopper, in a RCBS "Uniflow". It has about a
5/16" hold in it, which allows only a small amount of powder to
enter the drum with each pull of the handle. Seems to work real
well, but I must admit I haven't tried it with Unique yet; as I try
to stick with using Hodgdon's Universal.

Best Wishes,
Ala Dan, N.R.A. Life Member

rick_reno
August 17, 2004, 04:13 PM
I've got a RCBS Uniflow. IMHO, it's a piece of crap - charge weights vary too much to make it useable. I've actually taken my Dillon measure off my press and use my hands to cycle it over my Pact scale - the Dillon throws a very consistent charge.

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