Nitromethane is reputed to be a great sensitizer for NH4NO3. This page chronicles my efforts (mostly successful) to make reactive targets with NH4NO3 and various 'flavors' of nitromethane. The best recipe we found using nitromethane for reactive targets is the last one listed on this page.
After the April 2000 Boomershoot I decided I needed to make the mixture more sensitive. There was just too many solid hits without the corresponding boom. I had been adding naphthalene in place of some of the diesel in an effort to get a gaseous fuel in the carton that would not need the heat of vaporization in order to get up to ignition temperature. I decided to try reducing the diesel even further and see if that would help. The day was kind of cool for July 4. About 60 F with the targets in the shade.
The following ingredients were used: 1 C NH4NO3, 1 C KClO3, 0.25 C naphthalene, 1T diesel, 0.5 tsp Baking soda.
All cartridges were chronographed at about eight feet and then
target velocities estimated:
Wrong direction in the sensitivity.
So, on to the racing fuel with 45% nitromethane. The following ingredients were used: 1 C NH4NO3, 1 C KClO3, 0.25 C racing fuel, 0.5 tsp Baking soda.
I have another batch of racing fuel that I want to try. It is 60% nitromethane. The mixture using it will be: 2.5 C NH4NO3, 2.5 C KClO3, 0.75 C racing fuel (60% Nitro), 1T MnO2, 1T Baking soda. I expect it will be better still, but some safety checks will have be done with small quantities first. Friction and spark/fire will be the first. The down side is that it is more expensive. About $1.30/target.
I tested the 60% nitro mix. It passed the friction and spark/fire tests without problem. In fact it seemed rather insensitive. When I finally tried detonating it, it was a disappointment. It would not detonate with the CCI Stinger .22LR. It was a very hot day and I let the targets "cook" in the sun for a couple hours before I shot them. They did go off just fine with the 2600 fps .223 FMJ's. I also left a couple targets in the cooler under ice for several hours and then packed them in ice for detonation test. They detonated with the 2600 fps FMJ's without problems.
At this point I don't really know what caused the difference. I changed three variables at once. 1) the fuel, 2) Addition of MnO2, and 3) Time between mixing and detonation.
My next test will probably be the 45% nitro with the MnO2 with and without time spent in the sun.
I tried using Coleman fuel and then acetone instead of the diesel or other fuel. The resultant mixtures were not as sensitive as the 45% nitro racing fuel mix. They would detonate with .223, but not the .22 LR. Without MnO2 the racing fuel mix would detonate with .22 LR (CCI Mini-Mag +V). With MnO2 it would not! I even tried mixing the KClO3 without grinding it and without grinding the prilled NH4NH3. 1/2 C of the 45% Nitro racing fuel, 2 C KClO3, and 2 C of NH4NH3 in 1/2 pint milk cartons would detonate with a velocity at the target of about 1350 fps -- 4 out of 5 times. See the video (Four out of Five ain't bad) of the reactive target tests.
Based on a tip from an Internet discussion group I revisited the 60% nitromethane racing fuel. In fact I did it without any KClO3! I mixed two quarts of NH4NH3 with 1/2 Cup fuel. I put half of the mixture in a one quart milk carton, then mixed in one tablespoon of 200 mesh Al powder in the remaining mixture and put that in a different one quart milk carton. About 90 minutes later with an outdoor temperature of about 35F I shot each of them with a .30 caliber, 125 grain, Speer TNT bullet with a target velocity of about 3470 fps. The first one exploded, the second one was inconclusive. It made a mild pop sound, but it could have just been the sound of the carton disintegrating from the overdriven (Speer says max velocity is about 3100 fps) varmint bullet. More tests are needed.
The key item here is that the NH4NH3 is more sensitive when the mixture is not in complete oxygen balance. In fact it is oxygen rich. This was the "nugget" I picked up off the discussion board. The "correct" amount of fuel should have been about 0.8 C instead of the 0.5 C that I used. When I added more fuel, the Al, the mixture apparently was not as sensitive. And of extreme interest to me is that no KClO3 was used. The KClO3 is the most expensive and dangerous item in the usual mixture. But I hit this mixture with more than anyone could reasonably be expected to hit with at the Boomershoot. How sensitive is it? Can I get the sensitivity down to .22 LR levels? More tests are needed.
I obtained some pure nitromethane and tried it. I mixed 2 C of prilled NH4NO3 with 0.4 C nitromethane, and 1 C of KClO3. They were put into 1/2 pint milk cartons and sealed. The ambient temperature was about 35 F. .22LR (CCI Mini-Mag +V were the fastest tried) would not detonate it, but 7.62 x 39 Russian HP would.
Next I mixed 1 C prilled NH4NO3, 1/4 C methanol and 1 C KClO3. Again it was put in 1/2 pint milk cartons and sealed. Again the .22LR ammo would not detonate it, but the 7.62 x 39 Russian HP would.
Next I mixed 1 C prilled NH4NO3, 0.4 C methanol and 1 C KClO3 (close to a stoichiometric mixture). Again it was put in 1/2 pint milk cartons and sealed. Again the .22LR ammo would not detonate it and the scope mount (that is being generous) on my SKS came loose and I was unable to get a hit.
Next I mixed 2 C prilled NH4NO3, 1/2 C 40% nitromethane racing fuel (I was unable to find more of the 45% fuel I had used in previous experiments), and 2 C KClO3, and about 1 tsp baking soda, and sealed it in 1/2 pint milk cartons. This detonated with .22LR (CCI Mini-Mag +V) from my Ruger 10/22.
This is very interesting to me. The racing fuel is composed primarily of methanol and nitromethane and works great for a fuel for the reactive target mixtures. Yet individually those components do not work as well. Oh, well. I have something that I'm happy with for the next Boomershoot. After that I will probably test out some suggestion from people that have read this page and have done their own experiments.
I mixed up four cups of NH4NO3 with 1/2 cup 45% nitromethane racing fuel and put it in a 1 quart milk carton. I put this carton in a two quart carton. I then mixed up two cups NH4NO3 with two cups KClO3 and 1/2 cup 45% nitromethane model racing fuel and filled the remainder of the two quart container with this. This was shot with a .22 LR (CCI Mini-Mag+V) from the Ruger 10/22. BOOM! We looked for left over prills of NH4NO3, but it appears that it all detonated, there was a fair amount of shredded paper left, but no prills. This is great info, it allows me to reduce the cost of these size (two quart) targets by nearly a factor of two.
I had put two 1/2 pint targets built on March 2, 2001 (see March 3 update) with the 40% racing fuel in my explosives magazine for storage tests. Today I carefully removed them from the magazine and tested them for safe handling and then for ease of detonation. Both appeared stable for handling (CB Longs failed to detonate them) and both detonated on the first shot with American Eagle 36 grain HP .22LR ammo fired from a Ruger 10/22.
This is the mixture to be used for the 2001 Boomershoot. You may wish to cut it in half or even by a factor of four when you are first trying this:
There are probably more cautions to be made that I can possibly remember. The risks are many. I wear a flak jacket, face mask, gloves, and hearing protection while mixing the materials. Here are just a few of the other things I can think of off the top of my head that should be a concern to you:
With the help of my friend Ry we did some more tests We found that we could cut down the amount of KClO3 and still get reliable detonation with a high velocity .22 LR. We (Ry came up with the names actually) call the mixture above 441 and the new one 631. Six cups of NH4NO3, three cups of KClO3, 1 cup of model racing fuel (40% nitromethane), plus the baking soda as above. Since the KClO3 and racing fuel are the most expensive components this cuts down the cost some.
The 631 mixture was used for the 2002 Boomershoot.
Email: Joe Huffman