Large vs small metering screw RCBS Uniflow


PDA






mxl
March 3, 2010, 06:55 PM
I am a newby and recently bought an RCBS Rock Chucker Supreme kit. I load .380, 9mm and .45 acp. The Uniflow powder measure appears to be outfitted with the large metering screw assembly. My question is: is it worth spending more to get the small assembly for more accuracy? I usually meter less than 6 grains of powder. I check it with a scale and the amounts appear to be consistant with very little variation--yet I have read the smaller assembly is more accurate than the large. Is the difference significant? Your thoughts and observations are appreciated.

If you enjoyed reading about "Large vs small metering screw RCBS Uniflow" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!
NuJudge
March 3, 2010, 07:04 PM
In my opinion, probably not. I regularly use my RCBS measure with the big screw to measure 3.8gr charges of WW231 for my Beretta 92FS. I do like the Micrometer screw, however.

Try the Measure with the kinds of charges you are going to use. Throw a couple charges to move the settled/packed powder out of the bottom of the measure, then throw 10 charges, measuring each. Make sure you use a consistent technique. If you are not satisfied, perhaps consider getting the small one.

Be aware, there are some powders that are great for performance, but won't measure well through any measure. 800X must have been sized and shaped just to be contankerous, but it shoots great in the .45acp. For such powders, set the measure to throw a charge consistently on the light side, and use a trickler to adjust.

billybob44
March 3, 2010, 07:29 PM
In my opinion, probably not. I regularly use my RCBS measure with the big screw to measure 3.8gr charges of WW231 for my Beretta 92FS. I do like the Micrometer screw, however.

Try the Measure with the kinds of charges you are going to use. Throw a couple charges to move the settled/packed powder out of the bottom of the measure, then throw 10 charges, measuring each. Make sure you use a consistent technique. If you are not satisfied, perhaps consider getting the small one.

Be aware, there are some powders that are great for performance, but won't measure well through any measure. 800X must have been sized and shaped just to be contankerous, but it shoots great in the .45acp. For such powders, set the measure to throw a charge consistently on the light side, and use a trickler to adjust.
Not to flame (much) but, NuJudge, if my powder measure would not throw pistol loads due to powder mfg. than it's time to change powders. Using a trickler for pistol loads sure would be Slowwww. mxl, I have two RCBS Uniflow powder measures, one with the small drum/screw, and one with the larger drum/screw. If 10gr. or over, I use the large drum, if under 10gr., I use the measure with the small drum. Call RCBS, tell them your problem, they will work it out with you--May be at no charge??

JimKirk
March 3, 2010, 07:30 PM
I have had good results with my Uniflow too, it has the large micrometer stem.

Check out this link for lots of info on the Uniflow read post number 16 for a test I did with mine.

http://www.thehighroad.org/showthread.php?t=505079&highlight=Uniflow


Jimmy K

hydraulicman
March 3, 2010, 08:28 PM
I have the same kit.

I have experienced some binding throwing small charges smaller than 5 or six grains of unique . I can't help but think the small insert would solve that problem.

other than that it works like a charm and meters w296 like a champ

Jesse Heywood
March 3, 2010, 08:39 PM
My experience throwing small charges with the large micrometer was not good when I went under 4 grains. First, if you don't have a baffle you need one. Instructions for making one are here. http://www.thehighroad.org/showthread.php?t=366367

When I went to buy the small cylinder and mike they were not available. So I bought the conversion cylinder for the quick change with the small metering screw. It also allows you to insert a drop tube and drain the cylinder. But it does not have a micrometer, so you are setting blind. Once I made the conversion I was wondering why I didn't buy the QC measure in the first place. It is very accurate measuring between 2 and 15 grains, which is all that I have tried. And for me, the drain was worth the conversion.

mxl
March 4, 2010, 10:22 AM
Thanks to all for the input. I had already made a baffle out of an old credit card.

cougar1717
March 5, 2010, 02:08 PM
I have a Uniflow and have used both large and small cyllinders with the standard stems. After trying them both, I don't think it really matters which one you use. Do not assume that the small drum will have less variation in charge weight. I think the small drum "cuts" the powder less - or makes it less noticable, but the .1-.2 variation in drop weight occurs regardless of which cyllinder you use. Plus, I really dislike having to change the cyllinder to drop more than 50gr. This is probably not a big deal for you, but if you use it for rifles and handguns, it's something to consider. I just keep the large cyllinder in it and go.

mxl
March 10, 2010, 12:19 PM
Update: I just called RCBS customer service and was told the smaller metering assembly would probably be more accurate for smaller loads--like 3-6 grains for handgun ammo. I explained I'd recently purchased a kit that came with the large assembly and I load only handgun. I then asked a question about price and the response was they would send me the small assembly for FREE!!!! Now that's good service.

If you enjoyed reading about "Large vs small metering screw RCBS Uniflow" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!