Unfortunately I haven't had a chance to fly the cluster yet. The rocket is in its final stages but not yet complete.
So what is it you like about the bkno3? How does the burn differ from the thermite? I live in AZ, but you can always PM me with the info. I'm leaning towards using the ML pyrogen, but at some point t I'd really like to use the thermite. Maybe on a bigger motor cluster.
Thermite sends a fiery ball of copper plasma particles down the motor core.When the molten copper hits the grain it lights instantly. Wonderful stuff IF YA KNOW how to use it. Without a mentor I would not try.
Mixing with nitro cellulose turns it into "just another ignition source" although a bit faster than most, not instant on,which is desired in clusters. Be extremely careful, if it goes off unexpectedly you will find your skin'clothes burnt to the bone [on hands] by molten copper. I have personally seen this, it's very scary & PAINFUL> You think hot wax hurts....ain't nothing compared to molten metal!
BKNO3 {Boron Potassium Nitrate} is the proven reliable ignition source for many military,sounding and NASA rockets. It works regardless of temperature by giving off huge amounts of extremely hot gas, which lights motors instantly. Is safer to handle, store & use during the igniter making process.
Thermite is placed 1/3 down the core from top, or you may actually blow the igniter out before lighting motor. Making the igniter involves placing powder in tube shape or "saddle" shaped charge wrapped over a dowel, then inserted into motor. This process is the most reliable I have used [in over 100 motors & drag races] and seen used. I made 17 gram charges for Vern's 1/3 Saturn project several yrs ago lighting 5 motors...M'N's
Since reading a 500 page 'Igniters for military" pdf I found BKNO3 one of the best, easiest to obtain & use. There are others.....Zirconium...Teflon/Mag..Vitron [Viton?] etc. But day in and day out you see BKNO3 being used by professionals everywhere. Just look at above post for the Saturn 5 By varying the size and amount of pellets, anything can be lit. There is no problem with heat transfer between granules, it works just as well in space as it does in atmosphere.
Problem you have is trying to light very small motors with tiny core/C-slots ...is getting something to fit.
If a match fits through the nozzle of the 205's, I would use broom straws, small skewers for shish-la-bobs to hold up my charge made from, tiny corner of baggie with 1.5 g's of thermite attached 2inches from top and inserted into motor. Do NOT test for continuity at the pad, unless you have tried it with a match before.
Try with 1 motor in a rocket first before lighting 4! You might also try making a dip with thermite and dipping a match. It will be slower, but so what, as long as all 4 pressure up at same time. If you are going to do this, learn how properly. This requires some time making and testing igniters till you find what works for your situation. A skill that requires some time.
The best way to light small motor is by pressing a BP pellet into top grain and just using a match ala CTI. But you want to use single use motors ruling that out. Reloads are a simple matter to push a BP pellet into grain & pellets can be harvested from Estes motors.No point going into all that, single use rules out using them.
Actually if you can't figure something out. I would try 4FFFF BP mixed in nitro and dip some matches, to see how well they work. I know some who make all their ignition supplies that way. Just don't dip too many coats or the match may blow the dip off. There are so many tricks & tips to making this stuff, a mentor is my best advice.