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Old July 13, 2012, 12:26 PM   #1
Stressfire
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RCBS Uniflow Accuracy?

Well, I loaded up my first live batch last night - only 20, that way if I screwed up, it wasn't a huge waste of resources.

Anyways, following recommendations of forum and books to down-load a bit when new, I set up scale (Lyman Ohaus D5) for 4.2 grains and adjusted the screw (bolt?knob?) on the Uniflow Powder Measure until what was being dumped weighed out correctly.

As I went along, I was measuring every 5th round or so (sometimes more often) and was finding that while many weighed perfect at 4.2, I was getting variations up to 4.5-4.6. It is probable that some loads were seated in that "higher than I wanted" condition.

While I don't believe I am in any danger of an overload, I would think the powder measure would be a little more accurate than that. Are these 1/10 - 3/10 gr. variations acceptable or is there an adjustment I am missing? Or is there something wrong that needs to be examined?
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Old July 13, 2012, 12:40 PM   #2
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Do you have a baffle in it? What type of powder... ball, flake, stick? How long is the drop tube? Are you "cutting" powder at the throw end? Is the bottle full and do you top it off as you go? What is the humidity in your area? Some or none may be applicable.

Perhaps you need to develop a more consistent "throw" when moving the lever. The speed of movement and the upper and lower "taps" should be as repeatable as possible.

1/10th a grain variation (or less) should be the norm... not, according to your numbers, as much as 4/10ths.

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Old July 13, 2012, 01:05 PM   #3
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Quote:
Perhaps you need to develop a more consistent "throw" when moving the lever. The speed of movement and the upper and lower "taps" should be as repeatable as possible.
+1 you should be checking every charge till you are sure you are consistent.
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Old July 13, 2012, 01:08 PM   #4
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You can usually get spherical powders to throw ±0.1 grain or even better, but everything else will normally spread out a little more. After checking every fifth round, when you get about 30 of them, find the average. That's where your measure is actually set. Adjust accordingly, so half the errors are low and half high. That'll keep you closer to what you want.
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Old July 13, 2012, 01:17 PM   #5
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Baffle - I do not believe so

Powder is Bullseye

I do not believe it is cutting - granules appear uniform.

Bottle was not "full" - since I did not plan on loading many rounds.

Humidity was likely around 40-50% in my area last night.

Quote:
Perhaps you need to develop a more consistent "throw" when moving the lever. The speed of movement and the upper and lower "taps" should be as repeatable as possible.
I was most definitely not aware that the speed of throw made a difference. For the most part I raised the lever rather slowly - may have gone faster on some of them
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Old July 13, 2012, 01:24 PM   #6
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What happens is motion and vibration settles the powder, changing its bulk density in the metering cavity. I would not count on better than ±0.2 grains with Bullseye, though if you get your tapping and feel down, it can do better. Flakes don't cut, per se, in the Uniflow, but if you get them too densly packed they can offer some noticeable increase in resistance to rotation of the cylinder.

Midway sells a baffle for the Uniflow, but you can make your own out of a beer can or even cardboard. Just look at the design to get the idea. You fill the hopper to above the baffle more most consistent effect of gravity on the bulk density by packing. Keeping powder at a fairly constant level by frequent refreshing of the supply also helps limit error, but do throw a few that you return to the hopper right after replenishing to help the powder bulk density settle.

There is more baffle information in this thread.
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Old July 13, 2012, 01:35 PM   #7
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There ya' go. Unclenick has explained the specifics of the more critical elements of consistency that I listed in my first post. So... go forth and be a repeatable, consistent fellow!

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Old July 13, 2012, 01:46 PM   #8
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Alrighty, well I figured perfection out of the gate was a bit much to hope for

Thanks for the recommendations (and the technical info). Will definitely try the baffle - thanks Unclenick

So speed of throw doesn't matter so much as consistency of throw?
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Old July 13, 2012, 01:52 PM   #9
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Quote:
So speed of throw doesn't matter so much as consistency of throw?
Speed is a relative thing, without seeing what you're doing, it's hard to calculate. I assume it takes a little over a second, and perhaps as long as two seconds, to go from the bottom to the top and back to the bottom again.
What ever you do, try and do it exactly the same over and over again. Many use the consistent "tap" method where by the tap at the end of each stroke is the same... be it hard, soft or something in-between, it should be repeatable every time.
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Old July 13, 2012, 01:55 PM   #10
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Ok, I think I understand.

What's the smart play with the ones already loaded - pull and start over?
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Old July 13, 2012, 02:18 PM   #11
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If the rounds are below your manuals listed max, then shoot them if you are just checking function; however, if you are checking for accuracy then you need to pull and reload - measuring every charge.
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Old July 13, 2012, 02:33 PM   #12
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While I haven't tried Bullseye, I can say that my Uniflow doesn't care for Unique, another flake powder. I generally pour powder into the hopper until it's 1/2 to 3/4 full. I tap the side of the hopper to settle the powder, then start throwing and weighing charges until I get the screw adjusted. I get better results with the screw on the "front side" of the measure; i.e., the screw and handle alligned with each other and pointing down when at rest. This allows the powder to flow into the cylinder with the cylinder at rest and thereby eliminates the concern of, "Did I give the powder enough time to fill the cylinder?"

Uniflow will mostly throw +/- 0.15 grains with Unique for me; even better with a ball powder.
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Old July 13, 2012, 03:19 PM   #13
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I generally only use ball powder, and my Uniflow has been spot on accurate with ball powders. I quit using flake powder because of the metering difficulties - ended up measuring every single load of 700X on the scale to get them correct, then gave away what I had left of the powder.
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Old July 13, 2012, 03:19 PM   #14
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If the rounds are below your manuals listed max
Of the ones I caught, none were at or over 4.7 (I am also seating rather high at 1.15) which is my manual's (Alliant's free one) max load. However one I was thumbing through at the store referred 4.6 as max (Hornady).

Gun is rated for +p, actually loves +p, so pretty sure I wouldn't have a problem on that end - but I think I may just scrap 'em, figuratively speaking
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Old July 13, 2012, 04:30 PM   #15
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Quote:
I was most definitely not aware that the speed of throw made a difference. For the most part I raised the lever rather slowly - may have gone faster on some of them
I have always used the Uniflow where I am raising the arm, not the other way around as some folks do - and when I throw, I hold the handle between two fingers and move quickly so it hits the top of the range - this vibration and the way I do it gives me consistent throws with ball, flake or stick
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Old July 13, 2012, 05:47 PM   #16
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So speed of throw doesn't matter so much as consistency of throw?
I operate my Uniflow briskly with a definitive sounding tap at the top, and on the down stroke. Some folks use two taps, I use one, but the important thing is to get in the groove and be consistent. Tap with the same amount of force each cycle. It's noteworthy to mention giving a pause at the top of the stroke to allow the powder a moment to flow and fill the cylinder. The larger the powder charge, the longer the pause.
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Old July 13, 2012, 06:48 PM   #17
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A light tap, tap at the top is my technique.

Speed I would consider "briskly" best describes it.

Sent from HenseMod6.
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Old July 13, 2012, 07:30 PM   #18
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I found that if I let them drop I had the same inconsistency as you do with my uniflow. I now drop them on the upswing and they are within + -1. Alex
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Old July 13, 2012, 07:44 PM   #19
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Of my 3 uniflows, I find that each one has a different wear pattern so they behave differently. My small pistol one with the small micrometer cylinder and insert is heavily worn and very smooth. It will throw bullseye (5.0 grns) spot on time after time with the occasional 4.9 grns. I normally set it up so the load is a hair light but hits the desired amount most of the time and goes light rarely.

My rifle uniflow on the other hand does not do pistol powders well but is good at big charges (40 to 80 grns) because that is what I run though it the most.

My third uniflow is brand new. It has only seen a few thousand grains of powder through it and it is not consistent, not smooth at all. Either RCBS is just making them rougher or I have forgotten how they were new. Either way, I am sure it will wear in as I use it more.

The key is to use a baffle, keep the powder reservoir full and consistency. You have to just experiment and develop your own technique for accuracy.
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Old July 13, 2012, 07:50 PM   #20
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Interesting you mention that Peter. I forgot that when new, I put a light deburr and polish on the drum and frame of my powder measures. I've not used a "stock" powder measure in so long I forgot how snarky they can be.

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Old July 13, 2012, 09:45 PM   #21
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You didn't mention which drum you're using. The older uniflow had a very large cylinder in the drum, not very suitable at all for small pistol charges. The smaller cylinder would be better, but I wouldn't use it for less than 5 gn pistol powder(too much error). The newest model may be better. I keep minimum 3/4 full, and always do a consistent double tap(top and bottom). Lyman 55 measure is better for small pistol charges.
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Old July 14, 2012, 09:17 AM   #22
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Agreed. Get the micrometer drums and especially the small one. I have several of the older big drums and the lock screw adjusters. They were the first thing I pulled on my uniflows.

I should mention that my pistol uniflow is coming up on 300,000 rounds made. I am sure it has dispensed more like 400,000 rounds since it always takes a few extra to build up the setup.

These things take a bit of time to wear in but are lifetime investments.
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Old July 14, 2012, 01:36 PM   #23
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glicerin brings up a good point about the cylinder size.

Are you using the large or small size cylinder?

I started with the furnished large size, but soon purchased the small cylinder since I was only loading pistol rounds. I didn't spring for the $40 micrometer; honestly haven't seen the need for it since I can adjust and set the simple screw easily. If you are using the large cylinder, you may want to consider getting the smaller one.
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Old July 15, 2012, 06:49 AM   #24
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I have 4 of them now that I use for specific purposes. All but one were purchased off evilbay and all came with both Lg and Sm cylinders. I fully agree they take getting used to as far as stroke and rhythm. It takes quite a bit of use or practice to develop a repeatable action and hit your intended charge, but certainly not impossible.

I found that the smaller the charges the easier to miss the mark with in most cases. I have the small drum in the one set up on my 4x4 press. Probably the lightest charges I throw is around 5.5 to 6grs of Unique for my 45ACp. I have found some differing charges while throwing it but not by much. Due to the loads I am shooting with the cast boolits, I don't sweat what little it is off. With most of my other pistol rounds I use AA powders which flow through like water. With the press mounted measure there is really little you can do to influence the powder. It settles as you load and thats about it. I do tap the sides a bit before starting but once you start cranking out rounds it is mostly up to gravity, and the baffle.

The ones I use bench mounted I can easily keep within a tenth or so of my intended target load with either stick or ball powders. Like mentioned however it does take knowing how to tap on the up stroke and down stroke to hit those settings repeatably. This said "IF" I am loading to the top end of anything, I will simply dump in my measuring pan and weigh the charges individually. I do this so rarely however that it is a non issue. I usually pick loads which are in the middle and when I work them up I am throwing the charges anyway, so I get very close to or exact performance time and time again.

I really like to use mine to work up loads while at the range. Simply take the powders and check the settings on the stem with my scale then while at the range simply stay within those parameters while working from the low end up in 1/4 turn increments. This not only makes it easier to work with while at the range but is easy to repeat once at how to get the exact weight. Simply use the number on the stem plus the actual turns and your done. A lot of my load notes are listed as the powder used and 3+2 1/2 turns or similar.
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Old July 16, 2012, 02:37 PM   #25
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You didn't mention which drum you're using.
Mostly because I have no idea

Was a freebie that I got with a used Lyman Spar-T. I believe the previous owner was loading .45 Colt with it - large maybe? When I first tried it as it was set (measure bolt set to lvl 4?) just to get an idea of what the numbers on the bolt meant, it darn near filled the little scale pan to the brim - I didn't think to weigh that initial charge - was pretty easy to figure out that it was way too much.
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