There are now a total of five positions available for Boomershoot 2011. Sign up here.

At about 6:00 PM PDT this evening (Wednesday, March 30) positions 33 and 59 for Boomershoot 2011 will be made available to the general public because the current holders of those positions canceled.

After 6:00 PM go to http://entry.boomershoot.org/ to sign up.

Yesterday I delivered some more materials to the Taj Mahal, did some non explosive tests, took inventory, and did some maintenance.

One of the first things I did was test the new electric sifter. They claim a pound a minute for flour. If this translated to a 454 grams (one pound) per minute of KClO₃ (potassium chlorate) then it would meet our needs. At our peak production rate we produce a single batch of explosives in 1.5 minutes. A single batch uses 400 grams of KClO₃.

Last Thursday Ry and I had spent a considerable amount of time brainstorming how we might be able to make some modifications to it to “just let it run all day” so that even if it didn’t process the KClO₃ as fast as the flour we could probably use it to our advantage because it could continue to run when we took breaks and production was slowed for other reasons.

I was very pleasantly surprised to find it would sift nearly 2 kg per minute. Although there might still be some modification which will enhance its utility I think it will be a very useful addition even unmodified.

The other items I delivered were five gallons of ethylene glycol (car antifreeze), the 50 pounds of I bought on Friday, and a few dozen plastic containers to be used as a new target.

I still have to deliver the 275 pound drum of KClO3 in my garage and the electrical generator, but those will have to wait until the ground is drier.

I knew the ground would be wet and soft and I was prepared to carry most of the items (not the 50 pound item) by hand or in my backpack the 0.4 of mile from the road.

I parked by the road inspected the ground out past the main target area by the tree line and figured that if I chose the correct path I could make it. I was correct but it was much slicker than I expected and I spent a considerable amount of the time sliding sideways through the mud as I tried to change directions to hit the drier and more firm ground.

After crossing the field used for shooting I proceeded across the waste land to the Taj Mahal. There is one area without a culvert where the ground gets very soft with water running over it during spring runoff. I hit that spot as fast as I dared. Immediately after crossing it you must make a turn or you will drive head on into some trees. I again spent considerably more time sideways that I would have liked but I made the turn and tried to continue up the hill to the Taj. No luck. The ground was greasy slick and my four wheel drive vehicle  barely clawed its way out of the trees. Had I not been able to get clear of the trees I probably would have been stuck. I would have not been able to turn around or get sufficient speed to make it back through the standing water.

Here are some pictures:

The last 100 feet probably took close to a full minute as the vehicle slowly continued to moved forward throwing mud and digging into the ground until if finally stopped in the snow.

Here is a picture after I made it back to the road:

Coming back out was relatively uneventful in terms of risk of getting stuck but the muddy water splashed on the windshield which made for some interesting times as I tried to clear it and maintain sufficient control of the vehicle to keep it out of the swampy areas that would have meant an embarrassing call to my brother for help. He had advised me it was too wet to make it out there and back.

The Potassium Chlorate needed for Boomershoot 2011 Boomerite was delivered to my home in Idaho a few hours ago. Assuming the ground dries out enough to get it to the Taj Mahal by the end of April we just need some more target boxes, a few gallons of ethylene glycol, and the mystery ingredient (readily available from Costco in 50 pound bags) and we will have all the supplies we need for the next event.

On our recent trip to the Boomershoot site I walked the 150 meters from the road to clean up some left over targets while Ry waited in my vehicle. My size 14 shoes were close enough to snowshoes that I didn’t break through the crust on the snow and it was like walking on a sidewalk for me while Ry broke through and went in half way to his knees.

The first target I detonated was composed of the spill from another 850 gram target, a complete 850 gram target and a 200 gram target. Assuming half of the spill detonated that was about 1500 grams or about 3.3 pounds of Boomerite. This is a little larger than usual but not all that much. I shot it from 25 yards away and when it went off blobs of mud landed all around me and I was impressed with the thump I received from the explosion. Previously we had been setting off 200 gram targets from 25 yards and I was concerned that it didn’t seem that there was as much thump as I had expected. The only previous 850 gram target detonation had been from 470 yards and Ry reported it had the biggest flash he had ever seen and the thump seemed to be typical.

When I got back to the vehicle Ry reported the first explosion was quite remarkable. It was very thumpy. He also felt it before he heard it and he counted at least six echoes from it. He felt it before he heard it? Hmm… the shock wave had to be transmitted through the ground for that to happen. I did have that target on the ground as opposed to on a stake so the spilled Boomerite would get the maximum shock from the target so the ground coupling would be greater than normal. But how much faster does the shock wave travel through the wet ground than through the air? Would the 150 meters be far enough for the difference between the air and ground waves to be discernible?

A quick Bing search didn’t pop up anything for the speed of sound in water soaked earth but the speed of sound in water is about 1.5 km/s. The speed of sound in hard rock is between 5 and 7 km/s and the speed of sound in the air is about 330 m/s. Assuming the speed of sound in the wet earth was no faster than the speed of sound in water then the time to Ry from the explosion would have been about 0.1 seconds through the earth and 0.45 seconds through the air for a difference of about 0.35 seconds. This is easily discernible by a human. If the speed of sound is greater than the 1.5 km/s the difference increases.

Years ago when I had time to shoot targets at Boomershoot events I would shoot from the ground and it always seemed I could feel the thump from the explosion in my chest through the ground but I wasn’t quite sure. The thump through the air was quite noticeable too. This new data point confirms my impression from years ago.

I have been sick for days but Ry came over to Idaho with me on Friday night and yesterday we went to the Boomershoot site to do some tests. Boomershoot is May 1^st and time is getting short to make any last minute changes in the event. Ry has his own thoughts about the day on site and other ideas of potential here. I thought I would add a little more from my perspective.

At Ry’s suggestion, via conversations with http://www.ultimak.com/ (who blogs here), I found and purchased 100 each of some plastic containers to use for targets. These containers are actually made of a corn starch resin and are compostable. I was hoping that “compostable” would also mean “biodegradable”. Further research has revealed this is not the case:

PLA is not biodegradable in its “as-extruded” state. Instead, it must first be hydrolyzed before it becomes biodegradable. To achieve hydrolysis of PLA at significant levels, both a relative humidity at or above 98% and a temperature at or above 60°C are required.

I expected that UV light would break it down but again further research proves (from the previously linked document) that hypothesis is also incorrect:

PLA is also highly resistant to degradation by ultraviolet radiation, with no loss in elongation after 100 hours in Xenon arc testing, and minimal losses at longer exposure. Amazingly for a polymer that is readily consumed by microbes in composting, PLA does not support bacterial growth before composting.

This means that if we use these target containers we will have to pick up all the pieces of the targets that were broken but not detonated. As Ry pointed out in his post from yesterday the detonated targets are reduced to very fine shard less than 2 mm long and perhaps 1/10 that diameter. We were only able to find them because the paper labels we used to secure the lids retained a few of them throughout the explosion.

Another downside of the targets is that if you get an hit that does not detonate the target the back side of the target is blown completely open and the contents are dumped as shown in the picture below. But on the other hand it was easy for the shooter and spotter to see the target was dead.

This was a hit from a 50 grain Hornady V-MAX^TM traveling at about 1625 fps. Another target detonated from a similar hit (I had forgotten the satisfaction of seeing the view in the scope suddenly and silently completely fill with smoke followed by the ground shaking thump as the sound reached you 1.25 seconds later). And a third target received an edge hit without detonating. This is consistent with other tests on other target containers.

From the manufacturing and storage viewpoint these targets are awesome. They can be filled in probably 1/4 the time and with increased storage density.

We tested two different size targets.

One target size tested was the “32 oz Clear Rectangle Deli” which held about 850 grams of Boomerite. This compares well to the current seven inch square targets which contain about 900 grams of Boomerite. However the “active area” of these targets is significantly less. To be considered “a solid hit” the active area is only 4” x 5” compared with the nearly 7” x 7” of the previous cardboard box targets. We can get 16 of these targets into each of our storage crates which is a 33% increase over the 12 of the 7” x 7” cardboard targets.

The other target we tested was the “8 oz Clear Rectangle Deli” which held about 200 grams of Boomerite. This compares to current 3” x 3” cardboard boxes which hold about 215 grams of Boomerite. The active area is 3.25” x 4.25” which is a little larger than the current three inch targets about the same than the four inch targets. The current four inch targets contain about 385 grams of Boomerite. We can get 48 of these targets into each of our storage crates which is the same as the current 3” x 3” cardboard boxes compared to 18 of the 4” x 4” cardboard boxes.

On our way back to Moscow we talked about the test results and our major concern was that we expect there will be more spilled targets. An edge hit or failure to detonate results in a massive spill. This material must be cleaned up at the end of the day because it can spontaneously combust and result in unpleasant interactions with the neighbors. Later that night I figured out a way to easily spray the dumped targets with water and I had convinced myself we were a go for the new targets this year. Then I did the research on the UV resistance and biodegradability and am now mostly convinced we should not use them.

As of this minute my plan is to research some other plastic boxes (Ry found some and sent me links) before making the final decision on new target containers.

Ry says he is not a total bastard. This is true. But I sometimes have to scowl at some of his ideas. You have no idea what his mind is capable of. Ice cubes and water hoses are just hints of some of the things he has suggested for Boomershoot “improvements”.

I just got an email from Cafepress saying that if you use the coupon code FFEB1145 on orders more than $45 through tomorrow to get 15% off. Fine print follows:

Save 15% off for cafepress.com shop orders of $45 or more, excluding shipping charges, gift wrap charges and applicable sales tax. All orders must be added to cart from cafepress.com shops only. Excludes CafePress marketplace purchases (e.g. all products added to cart from URLs beginning with the following (i) http://shop.cafepress.com, (ii) http://t-shirts.cafepress.com and/or (iii) http://www.cafepress.com/sk/), Gift Certificates, Flip products, SIGG bottles, Thermos products, yoga mats and CafePress Make, Groups, and bulk orders. Coupon code FFEB1145 must be entered at check out. Promotion starts on February 24, 2011 at 12:00 a.m. (PST) and ends on February 25, 2011 at 11:59 p.m. (PST). Offer valid online at cafepress.com only, cannot be combined with any other coupons or promotions and may change, be modified or cancelled at anytime without notice. This promotion cannot be applied to past orders.

The Boomershoot Cafepress shop is here.

This morning the last “normal” shooting position for Boomershoot 2011 filled up. There is still one position available in the .50 Caliber Ghetto. People can and do shoot smaller caliber guns from this position it’s just that they don’t have access to the closer targets.

The .50 caliber positions are always the last to fill and frequently there will be one or more of these still available on Boomershoot day.

If you are interested in participating in Boomershoot 2011 but want some other position you should seriously taking a .50 caliber slot and let me know you really want a different position. I expect there will be more cancelations in the next month or so and people already signed up get first chance to take the open slot. If you don’t get the position you want you can still cancel and get a refund if you request it before April 1.

I received a Tweet from thumper242 requesting:

Can we get photographic proof of how ridiculous the temperature is in the Republic of Northern Idaho?

Here are some samples from the Boomershoot site last weekend. Click on them to see a higher resolution version:

The bush nearest the road at the tree line.

Looking north from just south of the creek.

The hillside we shoot into.

The Taj Mahal.

The top of the Wi-Fi antenna from a different angle.

The concrete blocks we use to put the tables on when manufacturing targets.

The snow in front of the Taj. Somehow my pictures just don’t capture how sharp, sparkly, and beautiful it was.

I dropped the plastic pitcher we use for scooping the ammonium nitrate onto the concrete floor. It fractured.

On Saturday I purchased a half pound each of three different colors of glitter. Then at the suggestion of Breda I ordered a pound of “Metallic Multi Color Mylar Confetti” this morning. The plan is to use the “Chalk Dispensers” as “Glitter/Confetti Dispensers” and see if that overcomes the problem with the powdered chalk turning into lumps.

The cost is $10/pound for the glitter and, after shipping, $15/pound for the confetti compared to about $1/pound for chalk. But a pound of confetti is going to have a much greater volume than either the glitter or the powdered chalk. The cost difference really doesn’t matter to me if we get the desired display instead of a few lumps of chalk falling, essentially unnoticed, from the sky.

Test results to follow within a month or so…