Ry, his kids, and I spent the day testing reactive target mixtures in two different types of target containers. We discovered the target bodies we used for the first time last year were part of our problem with failures to detonate. Those problematic target bodies will not be used for Boomershoot 2005. We also found modifications to our procedures and to our mix to make the mixture more sensitive. With the new mix and the new target bodies but with small sample sizes we got 100% detonations with .22 caliber bullets (CCI Stingers) going about 1420 fps at the target. We got 100% failure to detonate with a target velocity of 1170 fps which means the targets are safe to handle. We did not do sufficient tests to determine the actual threshold for reliable detonation but do not expect it to be much if any below 1400 fps. The new mix has a lot more “punch” to it that the old mix and there is a very noticeable flash.
High level view of Boomershoot reactive targets:
History of Boomershoot reactive targets:
In 2003 we changed to a new type of fuel that cut the costs considerably and make things more sensitive at the same time. Since that time we have kept the fuels proprietary. The mixes listed on the web page work and are “good enough” for most purposes but our later mixes give us an edge in some areas. Yesterday was spent testing new fuels, a couple of catalysts, and the target containers.
Boomershoot reactive target innovation:
Almost all of our innovation to make the mix sensitive enough to detonate (not ignite, that is something completely different) and yet safe enough to handle has been with changing the amount of potassium chlorate and using different types of fuels. This has been an ongoing learning experience. I have purchased probably twenty books and spent countless hours learning about explosives and the detonation mechanisms. Then a friend (usually Ry) and I would test my latest hypothesis on how to make the mix better. Most attempts were disappointments. Only occasionally would we have something that worked better than what we had used before. For the last three years we used the same components in the same proporitions with only an involuntary change in the grade of the AN we received from our supplier. Yesterday was the first time we had a significant advance in a long time.
Yesterday we took four new fuels with us but only had time to test three of them and only two in enough detail to be confident we found the “sweet spot” in the proportions. The two fuels insufficiently tested looked to be poor performers on paper and we probably won’t investigate those anytime soon unless the storage tests being done turn out very poorly.
We use two different oxidizers in our reactive targets. Ammonium Nitrate (AN) is the main ingredient and Potassium Chlorate (PC) is used to increase the sensitivity. These chemicals are mixed with a fuel to create an bullet sensitive mix.
The fuels we used will be called:
- Fuel 0–the liquid fuel we have been using since 2003.
- Fuel 1–new solid fuel which looked the best on paper but is a little difficult to find and slightly more expensive than some others.
- Fuel 2–new solid fuel which looked second best on paper, is very easy to obtain and is cheap.
- Fuel 3–new solid fuel which looked poor on paper but is commonly used in the fireworks industry, is easy to obtain and is moderately priced.
As many people know the discovery of Penicillin was an accident. And so it was yesterday for us. One of the changes we adapted was because I made a mistake on the very first batch. From a chemistry and common sense point of view we should grind the AN. We buy it in prilled form (spheres about 0.1″ to 0.13“ in diameter) with a very thin coating which protects it from moisture. But what we have found in the past is that either it didn’t make any difference (Boomershoot 2001, 2002) or better performance was achieved with only some of it ground. In 2003 our supplier of AN had fertilizer grade material instead of the usual explosive grade material. It sort of went “POP” instead of “BOOM!!”. We tried grinding the AN and it made a better boom but wasn’t sensitive enough. We ground half of the AN to get a compromise. Since then we have had the best results when half the AN was prilled and half was ground. Yesterday the first batch was made entirely with ground AN. Whoops! Well, rather than just burn it (our disposal method) we decided to box it up and test it. We found that with the present fuels having all the AN ground made a huge positive difference in sensitivity. Another accident was that we used just a small amount of Fuel 0 “to keep the dust down”. It turned out the presence of Fuel 0 was crucial to detonation. Without it there was no detonation even with a .223 at close range.
We ended up making 13 batches of reactive target mix. Each of the batches made from two to four targets depending on the size of the target and volume of fuel we used. Except when we intentionally left out Fuel 0 and only used Fuel 1 we could detonate everything with the .223 at 12 yards. The high velocity .22LR got at least partial detonation on most mixes. By observing the points at which we would start having failures to detonate we could bracket the acceptable limits of the proportions of the fuels.
We explored the limits of Fuel 0 and found that we had been using too much in previous years for optimum detonation sensitivity. We explored those limits and found the optimum proportion for maximum sensitivity. The power was a little lacking but the detonation was very reliable. We then adjusted the proportions of Fuel 1 for optimal sensitivity with the previously determined amount of Fuel 0. Fuel 2 was explored in a similar manner to Fuel 1. At the optimal levels of either Fuel 1 or Fuel 2 we could not distinguish a difference in performance between the two. Both would detonate in the new target bodies with the .22LR at velocities of about 1420 fps. And both would generate a significant flash upon detonation with a much better “punch” to the chest than mixes of previous years. Since Fuel 2 is cheaper and easier to obtain we decided it was preferable.
We tried optimal mixes of both Fuel 1 and Fuel 2 in the 6″ target bodies from last year. We could only get rare detonations with the .22LR at velocities of about 1540 fps. The target bodies were creating an effective loss in velocity of something well over 120 fps with the 32 grain .22LR bullets! The .223 would detonate them every time at these short ranges.
With the Fuel 2 mix we added Catalyst 1 and tried it again in the 6″ target body. We got one detonation out of four with velocities of 1540 fps. Not good enough.
We were in the process of trying Catalyst 2 when we had a big scare. I mixed the fuels with the AN and then added Catalyst 2. Within about five seconds there was a very strong smell of ammonia and I turned off the mixer and took the mixing bowl outside. There was no apparent heating or visible problems with the mixture but the smell was still very obvious. I dumped the mix on the burn pile for later disposal without ever adding the PC.
Next we tried Fuel 3 combined with Fuel 0 in the 6″ target bodies. Zero out of three detonations with 1540 fps .22LR. The time was 1700 and Ry and the kids had to leave. I stayed to make one more batch of the optimal Fuel 2 mix in the new target bodies for storage tests, cleaned up, and then came home later.
Next week Barb and I will go back and test the stored product for sensitivity and then a couple weeks after that we will test again.