i need some guidance just picked up a rcbs pro chucker 5 press seems solid my issue is with the powder measure it will not throw a consistent charge it's all over the place from 41.1 to 46.6 target is 42.3 it threw it one time. I have the rifle stem and additional spacer inserted is this common is there a better powder measure I should get any help is greatly appreciated

???????mike

I've had a problem with my measuring screw (per manual diagram) coming loose and really making my charges wander.  Make sure that's tightened down good.

What kind of powder?  

Something is way off. Your spread is way past normal for that size charge.

With stick powder, it isn't unusual to see 0.5 to 0.6 total spread over a population of 30 or more.

But that means you should only be seeing +/-0.25 or +/-0.3 grains from your average throw, and only after weighing something more than 15 of them. It takes a little while to see the real spread.

Something sounds wrong. You should be more like 42.0 - 42.6 or less with better technique.

Stop and check to make sure something isn't coming loose. Also, get some check weights and make sure your weight measurements are accurate.

Try running a pound of powder through it twice to lube it up if its new.

I am using IMR4155 and thank you for all the responses I did take it apart and checked everything I have to go over it again.  I also didn't think the charges even when running correctly would have such a spread this is going to suck for my bolt gun loads as I wanted them to be on the money at 42.3 is their any trick I can do?

Extruded powders are not going to measure balls on all the time.  The nature of any powder measure.

While the UPM is very good.  It is best when hand operated with consistent operation.  
Get a baffle
Keep the hopper half full or better

It needs to be mounted solidly.

When I use it.
I go up a firm motion and then back up and tap it to settle the powder.
And with a firm motion to dispense the powder.
Then I trickle up to the desired weight when using extruded powders.

Man I'm really regretting selling my single stage press right now taught I could be within +\-  .2 grains with this setup and speed up my reloading as I enjoy shooting but could do without the long nights loading. Once you got your load kinda takes away all the fun of the work up. I've seen plenty of people running a progressive for loading that shoot prs I wonder what measure they are using or trick if there is one. In either event thank you for the advice

Technique plays a roll in your results. In my experience the RCBS Uniflow measure is one of the worst when it comes to using extruded pwders.

IMR-8208-XBR
H322
VihtaVuori N140, N133 and even N150
AA-2015

All throw very well because they're fine grained  extruded powders. Even RE-15 isn't that bad when thrown.

I'm using a Harrell's Precision when I'm not running the progressive.

It still comes down to the operator of the powder measure.

Harrell measures are the cream of the crop for sure!  

My UPM with both lg and sm chambers with micrometers and baffle have served me well since the mid-80's.  And, at the same time.  
I know some that operate a Lyman 55 with excellent results, too.
Redding makes great powder measures, also.
Never been a fan of the Hornady, but....

A reloader has to hone their skill set!  Nothing happens overnight.

If I was to begin shooting 1000yd matches etc I would gear up with a better electronic scale and trickler

I have both just wanted to speed up the process as precision shooting isn't bench rest so a slight difference in a throw of-/+ .2  wouldn't make or break me I was in hopes of accomplishing this with this setup