BP question

[jbtynes]

I have a couple batches of BP that i worked down to smaller particle sizes than i wanted. I have since got my technique to produce what I am happy with. I decided to re-mill the small particle back to meal. Will I have trouble when wetting and screening this? I ask because I am not sure what happens to the dextrin once it is activated the first time. Will it properly bind when the second time around or do i have to add fresh?

 

I am new here but have found a wealth of information. I did search for an answer but came up empty.

 

Thanks in advance for any advice.

[dan999ification]

It will be fine ( pun intended ) in fact it may be better unless your bp is at the point of no returns.

My 3 hour bp is better after re-milling.

 

The same applies for charcoal stars since the kno3 is dissolved into the charcoal already.

 

Dan.

[jbtynes]

Well i originally screened it through 4 mesh. Then after it dried i tried to crush it down to around 20. I had lots of different size particles i had to screen out. The next time i screened through 12 mesh to start. These particles gave me a much better results and way less variations. I tested it by launching baseballs - roughly 8.5 seconds in the air with 0.8 oz lift charge.

 

Still learning and experimenting. Thanks for the input.

[bob]

I don't really like making four mesh and crushing it, I perfare to use a screen that is the same size as I want most of the bp to be.

At 22.7 grams for a 8.5 second flight it still needs some work, my 17 to 24 mesh bp gets a 8.7 seconds with 10 grams, however speed isn't the only thing.

How long did you mill it for? Yeah the dextrin will be fine.

bob

[Arthur]

If you sling into a snap top bag all the mesh cuts you don't like, you can damp it with 10% gross weight of warm water and at will soften into a putty again. Grate it again as needed.

 

As your powder seems a little slow maybe you could mill for another hour or so.

[jbtynes]

I appreciate the input. I didn't stopwatch that flight time, but it was fairly close. i will do some more this weekend hopefully and will take a video so i can time it later. BOB - I believe that was milled for 6-8 hours. I let it run outside overnight. What is recommended mesh cut for lift on 3-4" shells?

[Mumbles]

Your BP sounds pretty good from what you've told us. Even if it isn't the hottest BP on earth, you can always add a couple more grams and take care of that.

 

I use almost exactly the cut you described. I call it 4FA, but it's basically 2Fg in reality. I use -4+16 for lift and break for bigger shells, -16+24 or +30 for small shell lift and break, and everything that passes for priming and pressing spolettes.

[808goboom]

You will be fine....re-wetting dextrin based mix is completely fine....I re-wet dextrin based star mixes all the time and every time I re pump them, they become solid as a rock like before....

[dynomike1]

I have seen this before but i cant find it. What is the ratio for Bp & Cottonseed?

[Mumbles]

I've never seen a lot of input on that either. In a table in FAST comparing different burst charges, Shimizu mentions a 13:10 ratio of BP to cotton seed. I would assume that this is a pretty typical ratio in practice. Most of the other burst charges were between 13:14 and 13:10, so that seems like the right ball park.

[dynomike1]

So that would be like a 5 or 6 to 1? Seems like it would be more since cotton seed are heavier than rice per cubic in.

[FlaMtnBkr]

No, that would be 1.3 to 1.

[dynomike1]

Ok i'll try it.

[FloridaCracker]

I guess since they are heavier that means more black powder is being added. But if the coating looks thin don't be afraid to add a little more. Just keep good notes including the dry starting weight of seeds, so you know what you did in the future and can figure out how much BP was added once dry (if you don't measure along the way).

[dynomike1]

I'm not much on ratios but i thought 1.3:1 would be less than 5:1.

[Mumbles]

The ratios are by weight. Cotton seeds are generally used in larger shells, so the actual coating might be a little thinner. I seem to recall reading some study somewhere, in which they determined that approximately the same amount of actual BP in used in each shell no matter what the carrier is. If you have the same volume of cotton seed compared to say rice hulls, the cotton seed will weigh more, but should have around the same amount of BP on it. In doing this the weight ratios will look lower, but in fact the actual amount of BP per volume should remain about the same.

[dynomike1]

I just got through rolling some, i'll probably take a picture and start a thread for people that missed this discussion.

[LambentPyro]

The Dextrin will stay, even if your skeptical, you can always weigh in a tad more just to be safe.

 

When you dissolve 50 grams of salt into a jug of water, when you boil that jug of water down so there is no water left, how much salt will you have? Same concept.