3inch she'll burst

[Merlin]

I am new and starting with 3 inch shells. My first batches of BP won't burst a 1 inch by 3inch report tube. I sealed it well in fact it blew out through the hot glued fuse hole. I get the idea from reading posts bp is not so good for small shells. I was using BP coated hulls.

Goex went boom. I am using air float charcoal and ball milling.

I will try granulated next. I ordered lump willow to try.

I made up granulated KP and it burned far more vigorously than my AF BP but have not tried in yet.

My question is am I wasting time and money with BP and KP for 3 inch shells or will the 3 inches require a more potent burst ? I know I am a long way from success but I figured if my comps won't explode a large report they likely won't burst a 3 inch shell.

Any advise will be much appreciated.

[pyrokid]

In my experience, proper BP hulls will give a very healthy break from a three inch shell. If the hulls are a bit slow, a flash or whistle booster can be added.

 

The strength of KP bursts increases with pressure. In my opinion, there are better uses for potassium perchlorate.

 

It sounds as though your BP is the problem. The lump willow should fix that, it sure did for me. Conclusion: review your milling, granulation, and rice hull coating procedures. These optimized processes along with the switch from hardwood airfloat charcoal to lump willow charcoal should fix your BP problems.

 

There is a flash burst called apertura from Jopetes' PDF that uses a mix of KNO3 and KClO4 along with aluminum and possibly sulfur. The potency of this depends on the ratio of KNO3 to KClO4.

[Merlin]

Thanks pyrokid. There are so many opinions floating about for small shell burst I was beginning to think I was headed the wrong way. You are right it probably is a technique problem and the charcoal. I will keep trying.

[schroedinger]

With ratio of hulls to bp did you use? For these small shells go for a heavy ratio like 7-9:1 (BP:Hulls). Or try straight granulated bp

[Mumbles]

As Pyrokid mentioned, KP burns faster under pressure. This also means that you usually need a certain minimum shell size to get the most out of it. I've found that 4" is about as small as I could go. Some people will boost KP breaks in general or to make them work with smaller shells, but that is treading on delicate territory to me. It's way too easy to go from anemic break to salute doing this. I much prefer to use either a hotter burst, or control the break with the number of pasted layers.

 

However, the fact that KP burns faster than your BP is troublesome. It's normally not too impressive out in the open. The advice you've been given so far is great. BP can provide a good round break on it's own. I personally prefer not to boost my shells, but it's a common technique if you're not getting the effect you desire, and can help to hide some construction flaws.

[psyco_1322]

Did everyone miss that fact that he DID NOT granulate the BP?

 

You can not use the dust straight out of the mill, it won't burn fast, and it's not going to break shells or tubes for that matter. It must we granulated! You don't fill the inside of a shell with mill dust. Use it to coat some rice hulls. Needless to say, your bp should have some dextrin in it, 5% works fine, and can be milled in with everything else.

 

For 3" shells, just use 4:1 bp coated hulls (that's 4 parts mill dust, coated on 1 part rice hulls), and about 2-3g of flash or whistle. Dial the shell in from there, you should be fairly close.

[TYRONEEZEKIEL]

Hey said he coated hulls. I use 7:1 unboosted and it sure makes some nice 3s.

 

Your BP is the problem. With commercial airfloat you should have no problem brewing a shell. Having it just burn through the fuse hole means that it is extremely poor BP.

 

What are your sources on sulfur and KNO3. Elaborate on your milling technique as well as your rice hull coating process.