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Thread: RCBS Uniflow

  1. #1
    Boolit Bub BarkEater's Avatar
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    RCBS Uniflow

    Evening guys, I just purchased 2 used uniflows from a gentleman, both have some rust on the drums which I'm sure can be cleaned up. The question I have is...how low of a charge will these throw with the bigger drum ? The ones I have coming only have the larger drum. Thank you
    Mike

  2. #2
    Boolit Master OS OK's Avatar
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    Geez...I forget the number, it's pretty low...don't quote me, but... something like 8 grains of Unique but not consistent due to the wide opening on the metering drum, that's a rifle drum...much larger quantities of powder than pistol.
    You'll love the throw...just have to find a pistol drum for it.
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  3. #3
    Boolit Master
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    It's not really a question of how low of a charge you can throw. It's the accuracy of those throws. Especially with powder(s) like Bullseye and Unique (flake type). When throwing these you are typically in the single digit range weight wise. The small drum will throw these more accurately than the large.

    Motor

  4. #4
    Boolit Master
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    I have the large drum in my Uniflow, along with the micrometer adjustment. I'm too lazy to install the small drum, even though, I use it exclusively to throw 4 grains of Bullseye. I weigh, every so often, and charges always stay consistent. My reasoning is....... my two Hollywood powder meters don't have optional drum sizes and they too are consistent with very small charges of fast powders.

    Winelover

  5. #5
    Boolit Master Electric88's Avatar
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    I also have the Uniflow with the large drum and the micrometer adjustment. Just this past weekend I was throwing 5.2 grains of HP38 more consistently than I thought possible. It very rarely dropped a charge that differed, and when it did it was only by about .1 grain, according to my digital scale. I'm sure it could throw less and do it just as well. Best money I've spent on reloading yet!

  6. #6
    Boolit Master OS OK's Avatar
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    Quote Originally Posted by Electric88 View Post
    I also have the Uniflow with the large drum and the micrometer adjustment. Just this past weekend I was throwing 5.2 grains of HP38 more consistently than I thought possible. It very rarely dropped a charge that differed, and when it did it was only by about .1 grain, according to my digital scale. I'm sure it could throw less and do it just as well. Best money I've spent on reloading yet!
    Using the small ball powder is what's letting you guys get away with the large metering drum in small quantities like this. Flake powders would give you a migraine.
    Another trick is to throw 10 throws when dialing in the micrometer...say your looking for 3.0 grains, throw 10 throws and look for a weighing of 30.5 grains and you'll be right in the middle of a 3.0 grain throw, then those occasional .1'th variations will become even more scarce.
    a m e r i c a n p r a v d a

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  7. #7
    Boolit Master Electric88's Avatar
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    Quote Originally Posted by OS OK View Post
    Using the small ball powder is what's letting you guys get away with the large metering drum in small quantities like this. Flake powders would give you a migraine.
    Another trick is to throw 10 throws when dialing in the micrometer...say your looking for 3.0 grains, throw 10 throws and look for a weighing of 30.5 grains and you'll be right in the middle of a 3.0 grain throw, then those occasional .1'th variations will become even more scarce.
    It's been awhile since I've thrown Unique, but if memory serves me correctly I threw decently accurate charges of that in my Lee Perfect Powder Measure. That one also works pretty well with stick powder.

  8. #8
    Boolit Master Electric88's Avatar
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    But at some point I will likely look for the small drum and micrometer. Might just buy another Uniflow, as that would be easier haha

  9. #9
    Boolit Master OS OK's Avatar
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    I have the Uniflow, Little Dandy, Hornady, Lyman 55 & an old Redding...Each has it's own best application as far as Powders it will throw accurately and which press it works with but...if I could keep only one throw and had to live with it, it'd be a tough choice between the Uniflow & the Lyman 55...I think I'd keep the Uniflow, maybe because it's been on the bench 40 years and maybe because it's so easy to use and rely on...but, that 55 would be awful hard to part with.

    One of these days I'm gonna get one of those micrometer adjustment thingies just because they look cool!
    And am sure they are much easier to adjust.
    a m e r i c a n p r a v d a

    Be a Patriot . . . expose their lies!

    “In a time of deceit, telling the truth is a revolutionary act.” G. Orwell

    2018 is going to be a 'Jaw-Dropping Year' . . . 'The Year', the World was born to live . . .
    just, "watch your 6" .

  10. #10
    Boolit Master Electric88's Avatar
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    Quote Originally Posted by OS OK View Post
    I have the Uniflow, Little Dandy, Hornady, Lyman 55 & an old Redding...Each has it's own best application as far as Powders it will throw accurately and which press it works with but...if I could keep only one throw and had to live with it, it'd be a tough choice between the Uniflow & the Lyman 55...I think I'd keep the Uniflow, maybe because it's been on the bench 40 years and maybe because it's so easy to use and rely on...but, that 55 would be awful hard to part with.

    One of these days I'm gonna get one of those micrometer adjustment thingies just because they look cool!
    And am sure they are much easier to adjust.
    The micrometers are really, really nice. I was skeptical before I got it, but man was it worth it!

  11. #11
    Boolit Bub BarkEater's Avatar
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    Well now...so I might get lucky with my 5.5 grains of Power Pistol ? Haha Thanks for the info guys...I will keep you posted if I can get them cleaned up and working. I appreciate the input.
    Mike

  12. #12
    Boolit Man
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    Quote Originally Posted by OS OK View Post
    One of these days I'm gonna get one of those micrometer adjustment thingies just because they look cool!
    And am sure they are much easier to adjust.
    I just use the depth gauge on the back of my dial caliper:
    Click image for larger version. 

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    I ground the dome off of the screw...

  13. #13
    Boolit Master
    Jal5's Avatar
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    Quote Originally Posted by Kenstone View Post
    I just use the depth gauge on the back of my dial caliper:
    Click image for larger version. 

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    I ground the dome off of the screw...
    Fantastic I have to try this!!
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  14. #14
    Boolit Master

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    To get the most out of the micrometers on the redding and rcbs measures ( along with the "clicks" on my harrels) Once the best load for a rifle or handgun is found the setting is written in my one lyman manual on the data chart behind the data for that powder. Its also on the data cards in my note book, this is even more complete as the note book has the load work up card for each increment I tested.
    Mitoyo used to sell a 0-2" micrometer head ( for use on gages and other tooling) I had thought about using one in a powder measure for adjustment spindle. But I never got around to doing it.
    The calipers setting it should be very accurate and repeatable. Again this number should be written in the manual and or note book for future reference. Another Idea is with a given powder and measure it would be possible to weight a "zero" setting and one at X.XXX ( .050,.100) and see the difference. Then when starting with a new load divide by the charge by the difference and multiply by the increment should give you the setting to be very close. Since the measuring chamber is a straight bore a .050 increase with a given powder should remain the same amount thru the range.

  15. #15
    Boolit Master OS OK's Avatar
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    Quote Originally Posted by Kenstone View Post
    I just use the depth gauge on the back of my dial caliper:
    Click image for larger version. 

Name:	BestPic.jpg 
Views:	17 
Size:	48.7 KB 
ID:	209806
    I ground the dome off of the screw...
    Ha! Another one of those "Duuh, why didn't I think of that moments!'' (Smack to the forehead for good measure!)

    Thanks...I'll try that tomorrow.
    a m e r i c a n p r a v d a

    Be a Patriot . . . expose their lies!

    “In a time of deceit, telling the truth is a revolutionary act.” G. Orwell

    2018 is going to be a 'Jaw-Dropping Year' . . . 'The Year', the World was born to live . . .
    just, "watch your 6" .

  16. #16
    Boolit Master
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    Quote Originally Posted by OS OK View Post
    Using the small ball powder is what's letting you guys get away with the large metering drum in small quantities like this. Flake powders would give you a migraine.
    Maybe so, but since I purchased the RCBS Chargmaster, the manual dispensers are delegated to small charges of fast powders. Everything, over 5 grains, is dispensed by the CM. I dislike metering small charges on the CM because of the extra time it requires. Besides, the Uniflow and Hollywood's would just sit and collect dust.

    Winelover

  17. #17
    Boolit Master Bayou52's Avatar
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    I've been using a Uniflow for 40 years. In my experience, the large volume cylinder will not throw small charges of flake powder consistently. I used 700-X mostly, usually under 5 grains.

    The small volume cylinder throws these smaller charges of flake powder much more consistently.

    Bayou52
    Bayou52
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  18. #18
    Boolit Master

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    Most powder measures wil do their best at around the mid point of their range of charge. Much above or below and things get interesting. I have tested used a lot of measures from Lee auto disks to Harrels. The RCBS Lil Dandie and fixed rotor type measures seem to do better with the smaller charges. Ball powders tend to meter well because of the flow charicteristics they have. Flake powders and stick powders just don't flow as well and can be harder to throw good charges with. Size of the cavity and shape of the plunger affect this. Also the dia of the fill hole in the housing.
    The cavities dia can be adjusted smaller with a bushing and new adjuster stem with the correct sized head. The bushing machined to length of the drums cavity would be captive when assembled. Or it could even be glued or soldered in place. The new adjuster stem could easily be turned from a bolt or from stock. This would give a much smaller cavity dia and a more viable range of adjustments for a small charge. Going to NEF threads Ie 5/16 32, 1/4 32 3/8 32 would give finer adjustments also.
    I believe the RCBS uniflow chamber is around .625 in dia for large and .500 for small. A piece of brass tube .625 OD and .125 wall thickness would give a cavity dia of 3/8". With the as cast opening in the housing being close to the .625 dia or a little bigger. A piece of the same tubing glued into it And opened up a little in dia. May make for a very accurate repeatable measure for small charges. A lot of the Belding and Mull measure tubes were this same 3/8" dia Id and they were are very accurate measures.
    Another issue with rotary measures is consistency of operation, the more consistant you run them the better they work. Same speed rotation, same "bump" stop and drop, same time between throws makes a big difference. Even the powder level in the hopper affects them.

  19. #19
    Boolit Master OS OK's Avatar
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    One of the best things I did for my hoppers was to make drop-in baffles for them...keeps the head weight of the powder the same against the metering hole in the drum (from full to almost empty).
    Another technique is the double tap when I grab another charge fill and the double tap when I deliver the charge. The first double tap causes the powder to settle consistently in the metering hole of the drum and the second double tap insures that there is no bridging in the delivery tube...flake powders can do that.
    You have to become very mechanical in your technique of double tapping as when you tap harder you get more settling in the metering hole and a heavier load by at least .05 grain (1/2 a .1'th)...with a little practice and lots of practice runs verifying the charge weights and you'll get really good at it.
    When the throw is adjusted right in the middle of a load...say your delivering 3.0 grains and your 10 throw average is 3.05 then that slight too hard of a double tap will put you over and the same on the too light tapping side...it'll put you under at 2.9 grains.
    With a small ball powder those powder throws are amazing to work with.
    a m e r i c a n p r a v d a

    Be a Patriot . . . expose their lies!

    “In a time of deceit, telling the truth is a revolutionary act.” G. Orwell

    2018 is going to be a 'Jaw-Dropping Year' . . . 'The Year', the World was born to live . . .
    just, "watch your 6" .

  20. #20
    Boolit Man
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    Quote Originally Posted by country gent View Post
    To get the most out of the micrometers on the redding and rcbs measures ( along with the "clicks" on my harrels) Once the best load for a rifle or handgun is found the setting is written in my one lyman manual on the data chart behind the data for that powder. Its also on the data cards in my note book, this is even more complete as the note book has the load work up card for each increment I tested.
    Mitoyo used to sell a 0-2" micrometer head ( for use on gages and other tooling) I had thought about using one in a powder measure for adjustment spindle. But I never got around to doing it.
    The calipers setting it should be very accurate and repeatable. Again this number should be written in the manual and or note book for future reference. Another Idea is with a given powder and measure it would be possible to weight a "zero" setting and one at X.XXX ( .050,.100) and see the difference. Then when starting with a new load divide by the charge by the difference and multiply by the increment should give you the setting to be very close. Since the measuring chamber is a straight bore a .050 increase with a given powder should remain the same amount thru the range.
    Yes all that, and weighing a charge thrown with the screw out 10 turns from zero would establish a powder amount equivalent for one turn of the screw (weight divided by 10).
    For that reason, I filed a reference line on the head of the screw so I could count the number of turns out to get to an approximate setting.
    And knowing the thread pitch of the screw would allow you to adjust it relative to the caliper reference reading in .001".
    So if the thread pitch is 40 (like a micrometer), one turn would be a .025" change, 1/2 turn is .0125, and 1/4 turn is .006.
    Another fact to get you back to your referenced caliper reading quicker.
    This is getting deep...
    Last edited by Kenstone; 12-19-2017 at 01:30 PM.

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