How long should you mill your BP for?

[MWJ]

Here's a simple test I did with some BP I made with willow charcoal. I have a HF dble drum mill and I put 50 1/2" lead balls into each drum. I milled it for the first 6 hours, took a sample then 9, then 12 hrs taking a sample out each time. It looks to me like anything after 6 hrs is a waist of time. I can't see the difference between 6 hours and 12 hrs. Can you?

 

Here's the video:

Edited September 16, 2014 by MWJ

[nater]

I mill BP for 2 hours.

[Sparx88]

It may be just me but it says video not available.

 

I mill mine for a total of 10 hrs.

Once it gets to about the 6 hour mark, I need to open the drums and carefully with a wood spoon break up the clumping off the walls of the drum and mill it for another 3-4 hrs. Once it starts clumping it's pretty much done, it's as fine as it will get and milling much further will not do it much good as it will clump again in the first 1/2 hour. Thats what happens to me though, probably a little different than others due to my recipe maybe.

[MWJ]

It may be just me but it says video not available.

 

I mill mine for a total of 10 hrs.

Once it gets to about the 6 hour mark, I need to open the drums and carefully with a wood spoon break up the clumping off the walls of the drum and mill it for another 3-4 hrs. Once it starts clumping it's pretty much done, it's as fine as it will get and milling much further will not do it much good as it will clump again in the first 1/2 hour. Thats what happens to me though, probably a little different than others due to my recipe maybe.

Sorry, try it now I was editing it and had to wait until YT published it.

[MWJ]

I mill for 12 hrs normally but now I probably wont let it go over 6 hrs. Even after 12 hrs it didn't clump up at all so maybe I'll try 24 hrs just to see if it clumps. I guess the shorter it takes the less wear on your lead and mill.

[Mortartube]

A good guide before you even light some, is to rub some between your fingers. It should be as fine as icing sugar. No point lighting it before that stage as it won't be near it's premium point.

[mabuse00]

That kind of test is not suitable for judgement.

 

Try loading your BP/any other comp in spoletta or little rocket tubes and measure the time. If you have trouble concentrating on the stopwatch, make a video and use the stopwatch at your PC, so your experiment isn't ruined when you fail to hit the button in time

 

Try to exactly repeat the pressing process - increment size and pressure.

 

I have a comparable mill and although I did not get enough rpm out of it, after 3 hours there is practically no more improvement.

[pyrojig]

These mills are a waste of time IMO. I have one too, and for the limited amount of powder and excessive mill times , it is best to scour the internet for a 9-12# mill at least. This is where you can mill 1+# at a time and for 3H . Im not knocking the HB mills, but they brake belts easy, and just arnt designed to run any real weight., Just my two cents.

[paddy]

several years ago, i bought a rock tumbler (1 gal) from a co. called rockler..it was sold to polish stones,which gave my children and myself great joy..two years ago i started my pyro quest.. i dug it out and it is working great for any kind of milling i do..as far as the rubber belts are concerned,,i solved that problem by going to the dollar store and buying a large bag of rubber bands all different sizes..i use them whenever i need them..no problem...1$ two yrs.. i make 800 gm. batches of bp..without problem..just saying.......

[FlaMtnBkr]

Are you saying a rubber band will work as a belt? That can't be a very heavy duty rig.

 

And rubbing between your fingers only gets you so far. Once something gets to around 150 mesh it is no longer palpable and you can't feel any grit. 150 mesh BP would not be very impressive.

 

In my home made hobby mill with 30# of lead, I mill BP for 3 hours. I try to check around 2 and knock any BP loose that has clumped to the jar. Once it starts clumping it is essentially done and has reached a sufficiently small particle size to interlock and clump together. Even completely dry chems will clump because of this behavior.

[Carbon796]

Yes, you really need to do a spolette test, or Fire some test shells -preferred-. To find out when your BP is optimized, with your mill/supplies/charcoal. Everyone's optimum time will very somewhat.

[MWJ]

Yes, you really need to do a spolette test, or Fire some test shells -preferred-. To find out when your BP is optimized, with your mill/supplies/charcoal. Everyone's optimum time will very somewhat.

I agree, but right now I can only do the test you see in my video because of fire danger around here. Being a firefighter I can't afford to be stupid and start a fire somewhere off of my property. I'm sure you all understand. I can do more testing later on in the season or maybe one of you can do it now. I would love to see the results of a good test. I want to shoot some of my shells off so bad I'm going nuts. I did put my BP test back into the mill today too see if I can get it to clump up. I put 200 gr. in with all 100 balls in one drum, so far 3 hrs and no clumping. I did feel it before I put it back into the mill and it was like silk so I though I would try to see if I can get it to clump with more milling.

[nater]

I use my little harbor freight mill all the time and have yet to break a belt. It was not properly tensioned or aligned out of the box, but that was easy to remedy with the adjustments on the motor and pulley.

[MWJ]

Ok, Another 6 hrs in the mill with all 100 lead balls and with 200 gr. of bp. I have clumping and it seem a lot finer. I burned a bit and it's faster than the first batch of 12 hrs and 50 lead balls. So The conclusion for me is: use all 100 balls in one drum (leave the other drum empty but in place) and mill until it clumps. Right? Any thoughts on this?

[MrB]

The drum should be half full with milling media. To top it of, use about a quarter of the jar's volume of stuff t be milled. At that point it all starts to boil down to how fast your jar turns, and what size it is...

B!

[TSO]

I started with the 6lb mill, running both jars at the same time with 100 lead balls in each jar and 200grams bp charge, and milling for 8 hours or so. It worked OK, but needed improvement

I've been milling the past 2 days with the new improved 6lb mill. I did the mod of the drive roller with 3/4" tubing, ran 1 jar at a time with 250 .5"lead balls, and milled 200grams of BP in about 3 hours. The first batch was with softwood charcoal, and I thought damn that's fast when I did the burn test. Then I wondered if it was just the charcoal, or the new way I was milling. So I dug out some older BP meal from 2 years ago and remilled that 3 hours also. It was commercial airfloat, and it was OK at testing...after the new milling it was burning much faster. Not quite as fast as the softwood charcoal...but a definite improvement upon the follow up burn test.

 

I made the mistake of milling for 8 hours the first run after the new mods....BIG mistake. Just one great big solid ball of bp that I had to rub hard against a 20 mesh sreen to get back to meal. Anything over 3 hours seems to show no further imrovement of the bp.

 

That's my results...I liked them so much I ordered another one from Harbor Freight.

Tomorrow I'm going remill some willow bp.

 

Found a pretty good source for lead media on ebay

92%lead6%antimony2%zinc 300 .5" ball for $45 plus 5.50 shipping.

Edited September 18, 2014 by TSO

[dynomike1]

I mill mine 18hrs w/10lbs. of ceramic and 4lbs. of bp. You sure your chemicals are dry? I like ceramic better liter and holds up longer.

[FlaMtnBkr]

How big is your jar? 4# of BP and only 10# media sounds like the mill is far from optimized. Might be why you need to mill for so long.

[rogeryermaw]

ceramic takes longer because it is so light. the heavy weight of the lead is a large part of why it works so fast. since i got the thumlers, i can run 300-400 grams in about 2-3 hours with about 20 lbs of media. using pine, it makes pretty fast powder. a 12" line just flashes away too fast to measure the speed.

[TSO]

Is that the model B high speed? I'm toying with the idea of an upgrade next spring. I've been looking at the Extreme's Rebel 17..very similar to the Thumlers, or ordering the yellow 35lb mill with a 1 gallon jar from Hobfir. He has the 15lb mill with a 1 gallon jar but won't make any assurances as to whether the motor will handle the load of 30lbs or so. The 3lb rubber jars will work on the 15lb mill from Hobfir...I don't know if they'll work on the 35lb larger mill though. I guess I should check with him on that.

[rogeryermaw]

i don't think so but it is modified by increasing the drive roller with 2 steps of heater hose, first 5/8" and 3/4" over that. it's running at least 65 rpm. that may not be fast enough...i haven't done the calculation but the hex jar makes up for it.

[Mumbles]

The motors on the 1 gallon mill handle 30lbs of lead just fine.

[TSO]

Thank you sir..I kinda figured that the 15 lb mills would be good with a 30lb lead load..so I was suprised when he said otherwise.

I don't suppose you'd happen to know the rpm with that 1gal jar would you?

Did you have to mod the drive roller at all with the 1 gal jar, or was it already at an acceptable speed?

[dagabu]

The Thumblers Tumblers Model B does not have to be modified in any way but is much more efficient when running at 65-70 RPM.

[FlaMtnBkr]

Yes, ceramic is less dense and can need different amounts of time. But I can tell from those weights his mill jar is not properly charged. Which will effect milling efficiency and media life.