Powder Measures - Designing one, want opinions.

[AMProducts]

So I'm in the midst of designing a powder measure for one of my pieces of equipment, and I figure it would be pretty easy to add a few modifications to attach it to a stand and sell it as a stand-alone unit, or sell it as a replacement for the powder measures used on normal progressive reloading presses.

I'm using a bushing for setting the quantity of powder. While this is more difficult to fine tune, it is also more consistent and as long as the right bushing is used, nearly trouble free.

I know in the past that bushing type measures have not been popular, however my theory on that is that is mostly due to the fact that they are pretty limited to doing only small pistol powder charges. I was going to size this measure to doing .308 Win and smaller cartridges (~50grs of powder and smaller). Also, it would come with a set of 5 bushings to cover common loads.

I'm machining a prototype right now, however here is the design in solidworks:



I suppose given the configuration of it, it's totally possible to make an adjustable bar, but this may be somewhat out of scope.

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[deadshot2]

Bushing type measures suck for a whole lot of reasons than the ones you mentioned. Unless you're going to use the same powder charge forever, and there are no lot/lot variations in consistency, they are just not the way to go.

Adjustable bars are out there in several forms. Dillon bars are more than satisfactory for powders other than the "rat turd" extruded powders. The main issue with ANY powder measure that uses a "cavity" to measure powder is the inability of the dispenser itself to provide a consistent flow of powder and settlement in the cavity so the weight is uniform.

Have you ever seen Brand Cole's "Prometheus" powder measure? A hit among the LR shooters but also several years wait with a price tag just under $3k

Powder is dispensed in stages. First from a drum type measure like Lyman, RCBS, or Hornady's. Then trickled automatically onto a beam scale with optical sensors to stop the process when the EXACT measurement is reached.

What's really funny is that Cheap, Plastic, Ugly, Lee Perfect Powder measure regularly holds up as one of he best for uniform dispensing.

Why not take that design and merely make it out of real materials like Aluminum, Stainless, or whatever. Get rid of all that static prone plastic but retain the polymer "striker" system that Lee uses to avoid cutting granules.

Good Luck. You're attempting something that only a very few people have been successful doing.

 

[Stevenav]

Speaking as someone that has one of the Ugly cheap and plastic lee powder measures (good lord, having read Lee's modern reloading its hilarious to read why they CHOSE to make it the way they did because they wanted something that worked... and it actually makes sense when you read about their choices!!! And even if it's asthetically horrible to look at it genuinely works and works well what a shock!)

Deadeye (as usual) hits the mark. That plastic is static prone (and that means powder sticks in the chamber)

Therefore I'd suggest moving to polycarbonate 300 or 350 type material with an anti static coating Boedeker Plastics : Anti-Static Polycarbonate Datasheet

A static dissipating coating would be a godsend if applied to all the components.

But Lee did bring up one thing about powder measures. That all the records for most accurate rounds were done with powder done using volumetric measures.

Good luck man.

 

[deadshot2]

A static dissipating coating would be a godsend if applied to all the components.

But Lee did bring up one thing about powder measures. That all the records for most accurate rounds were done with powder done using volumetric measures.

Good luck man.

Just wipe the crap out of them (sometimes literally) with a dryer sheet. The static will eventually go away after they get a coat of graphite off the powder.

On "Records" yes, they are set using volume-metric measures------AFTER many, many loads were first weighed.

Once the shooter learned how his measure responded then they logged "clicks" or vernier settings.

 

[AMProducts]

Generally anything that touches explosives shouldn't be made out of a sparking or static holding material. I remember back in the day when I splurged my allowance on a lee perfect powder measure, god that thing was a pile of junk. I still remember loading .30-carbine and having the precious H110 get into the mechanism, clog it up, which then forced more of the powder into the mechanism until the whole thing just became useless.

For materials I was going to use aluminum housing with a brass charge bar, holding either a brass or aluminum bushing. So static cling should not be an issue. I will probably stick to plastic for the reservoir, just because aluminum isn't clear, and glass just seems like a bad idea.

 

[DieselScout]

Fast, Accurate and Affordable. By affordable I don't mean cheap. I understand great tools having a higher price tag and don't mind having to save to buy something that is going to last me decades.

FWIW, I could care less what it looks like or what it's made of. Form follows function.

 

[deadshot2]

Fast, Accurate and Affordable. By affordable I don't mean cheap. I understand great tools having a higher price tag and don't mind having to save to buy something that is going to last me decades.

FWIW, I could care less what it looks like or what it's made of. Form follows function.

You want to violate the rules of "life"? Of the Fast, Accurate, and Affordable, that's one of those things in life where you can't always have all three. You have to settle for two. If it's Fast and Accurate, especially if it's going to work on various consistencies of powder, you'll probably find it to be expensive. At least that's the current world of powder measures.

As for plastics? Remember all the furor when it started making it's way into cars. People screamed. That was until they found that you could back into the car behind you at a parking lot and when you got out to look there was no visible damage.

Some polymer parts are even stronger, do a better job, and are more affordable, than the metal parts they replaced. For powder dispensers clear polymers are available that have transparent metallic coatings. The coating draws off any static electricity. Only issue is that this "extra" has a price.

In the business I retired from there was a saying:

"You can have Excellent Quality and Performance, Superb Service, and Affordable Price. The only problem is that you can't have all three at the same time. Pick Two".

Pretty much true with everything in life.

 

[CarlMc]

Generally anything that touches explosives shouldn't be made out of a sparking or static holding material.

If this weren't a scientific sandbox I play in, I'd agree with you. The size of your grocery cart means it can store enough charge to give you a good sized zap, and its wheels are the constant generator of the static electricity. The small size of the powder measure and very slow charge generating mechanism means that the static is merely mild and annoying, not something capable of storing enough charge to ignite the combustible contents (technically not an explosive.)

Soapbox off!

 

[Stevenav]

I think that plastic is the clear (no pun intended) choice there. Here's the thing, I used to work for a company in spokane that tested thin film coatings. There are thin film coatings out there that could be applied to the inside of the plastic to help reduce or eliminate static from the powder grains rubbing against it. Just raising the suggestion on that again.

As to the powder chamber, I'd suggest machined aircraft aluminum, nickle, brass, or ferric stainless steel. With that you can maintain exacting standards for precision of both the chamber and whatever you use to vary the capacity altering feature. I'd suggest using a threaded volume measure like lee uses, only have a locking feature with an open and closed lock point for adjustment and a measure indicator line that has actual meaning. The lee doesn't have a "this is when it's closed" and "this is when it's okay to spin the screw" indicator and as such you aren't too sure about what your actual volume measure is at any moment till you screw it down and measure. You have to pour and weigh and then adjust, pour and weight, and adjust again and again till you get it right.

sticking to a good material will make sure temperature has a less significant effect on amount dispensed.
The linear thermal E& C coefficients for each of them shows why they'd be better for the chamber than plastic with volumetric values being even higher.
E&C for plastic ranges from 66.8 to 202
Aluminum has 22.2
nickle 13.0
brass 18.7 (bronze) 18.0
ferritic stainless 9.9

Of course the ferrous metals risk rust and corrosion.
Nickle would be best imo due to its strong resistance to corrosion, as would brass or coated aluminum though.

temperatures can cause the measure chamber to shrink or enlarge slightly, and with very tiny amounts making a big difference you might want to have as little expansion and contraction as possible due to temp variation. Just a thought.