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Det Cap Strategies

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ManyInterests - 13-8-2024 at 15:44

I HAD one of those... and I accidentally broke it today! I will be buying another one to replace it.

And yes, I'll be working towards finding the minimal foil. This is for the steel caps (and later the aluminum tube when it arrives). For now I will focus on processing my shell casings. Punching out the primer is harder than I thought, since I don't have reloading tools (yet). So I drilled through the back. I noticed that the 7.62x39mm is MUCH thicker than the 5.56x45mm! I broke a drill bit in the process! Another tool to replace!

Quote:

Well done on the tests so far, what was the mass of EM in each of your test caps?

I'm actually quite proud of my latest test overall. If the new mostly bottomless steel caps can exceed that, then I think I would have achieved my goal of making a blasting cap that is on par with the commercial or military caps. When I read the Improvised Munitions Handbook section on detonators (and I should have memorized it better, since it had some information that could have made my life much easier) the warning at the end really captivated me 'Detonator has considerably more power than a military blasting cap and should be handled carefully'. I don't know why, but just that made me really, really want it!

UndermineBriarEverglade - 14-8-2024 at 23:57

First cap. 7mm aluminum tube closed with foil. 250mg of ETN hand pressed to 1g/cm³ (

), plus 50mg loose, detonated with EBW. 1mm steel plate. Bucket of cat litter worked well to muffle sound. I guess I should increase the charge amount?

Sir_Gawain - 15-8-2024 at 08:55

Definitely increase the amount. I would add a third layer of ~500 mg ETN pressed or cast to high density. I used 500 mg melt cast because pressing to high density in thin aluminum tubes can cause them to deform. I also figured it would help seal the end of the tube.

ManyInterests - 15-8-2024 at 17:10

I feel jealous! That is actually quite impressive for a first time cap. I wish I could have had that kind of result early on!

That being said, I will concur with Sir_Gawain about melt-casting ETN. When you melt-cast powdered ETN and grind it back up again, it is of much higher density and you will see markedly improved results from similar weights.

For me I am going to make another 10 detonators to test for next time. This time I hope it will be finally... FINALLY the time when I succeed. I will do 4 steel bodies, all with the ends cut off, but 2 will have just electrical tape at the end to seal the other side (and only one layer) and the other 2 will have some foiled pressed and some tape to hold that in place. the foil isn't 100% unpushable, but it does need a thwack to get it loose. I hope that still provides the same purpose as foil.

The other 4 detonators will be 2 5.56x45mm/.223 and 2 7.62x39mm cases all processed as per the Improvised Munitions Handbook. Deprimed and drilled from the back, so the explosive train will start from the hardest and end in the softest. I will have one of each kind sealed with some foil and crimped mildly to hold it in place and taped, the other two will just be taped.

The final 2 will be made from the aluminum tube I ordered (which hasn't arrived yet). One with some foil and tape at the end and the other with just tape.

All loadings will be 1g of pressed ETN and 0.3g of 1:1 ETN:NHN mix as usual.

Laboratory of Liptakov - 15-8-2024 at 23:08

Finally I see pictures with entire assemble with tube. Good work with EBW. On picture is see damage of aluminium cavity. According all is it
full detonation 250 mg ETN. Damage of 1 mm of steel plate is little bit weak, but it can be cause aluminium tube. If should by the tube from steel, the hole in 1 mm steel would by bigger and rouded. Inner diameter is 7 mm ? 250 mg in inner diameter 7 mm is too small. This diameter require minimal 400 mg of ETN for output segment. ETN should by form a square height... :cool:

Laboratory of Liptakov - 19-8-2024 at 03:12

It was create control measurement at similar conditions. Thus aluminium tube 8 mm / 6.3 inner mm of diameter, aluminium foil on output segment 0,1 mm of thickness, (first pic). Construction steel 1.5 mm of thickness as target. Filling 250 mg ETN output segment pressed on 20 Kg. Primary segment from mixture CHP/ ETN 1:1 (on pic) and next filling from pure CHP crystalls. Plug from classic BP grain, also pressed on 20 Kg.
Result is very similar. Almost same hole in steel plate...... :cool:

pjig - 19-8-2024 at 20:37

Have to ask, but is the bp necessary to get the det train enough temp to get going , or is ematch, or the heat of 1/4” time fuse enough to ensure 100%ignition ?

UndermineBriarEverglade - 19-8-2024 at 21:38

Thanks LL! So nice to have a comparison. My tubes are actually 7mm outer diameter so inner diameter is only 6mm. The height of ETN was around 9mm (low density). Maybe the aluminum foil layer was too thick or the cap was not pressed tightly enough against the steel.

The next caps, I will use more ETN and maybe a reground melt-cast output segment. But maybe this is already enough to play with secondary explosives.

Laboratory of Liptakov - 19-8-2024 at 23:32

0.3 x 03 x 3,14 = 0,282 x 0,9 = 0,254 cm3 0,250g / 0,254 cm3 = 0,984 g / cm3. Really. Density was 1g /cm3. Next you can try 300 mg ETN high pressed + 200 mg for EBW segment about density 1g/cc. Any way, created full detonation using EBW nothing is taken for granted. Is it the successful itself...... :cool:

UndermineBriarEverglade - 20-8-2024 at 08:34

Yeah terribly low density. The small (rapid pour) acetone-formed crystals are very fluffy even when pressed hard. 500mg sounds good, I will melt cast a thin layer and then crumble it up to make the output segment.

ManyInterests - 20-8-2024 at 14:39

With ETN my suggestion is to do at least two recrystalizations. I do the first in acetone, and the second one in methanol. The hot methanol (not too hot! not at the melting point of ETN!) will make a nice fine powdery texture. Use urea as an acid scrubber in both. I use both urea and some sodium bicarbonate or carbonate with it as well. This will make sure that no acid is left over in any for your ETN and you will be able to store your stuff for years without issue.

For me I got an update. My aluminum tube just arrived. I cut out 4 70mm lengths. 2 of which I bent on the other end to hold in 5mm worth of aluminum foil jammed in (one of them had a rather ugly bend, but there is still a good opening on the other side), and the other 2 are just taped at the end.

Edit: for the ones with aluminum plugs in some take up from 2 to 5mm of space. Is this too much?

I made them longer than needed because I want to make sure I have enough space for the energetic material.

So in the end of the day I will be testing 16 detonators! The final one I hope.

[Edited on 21-8-2024 by ManyInterests]

dettoo456 - 21-8-2024 at 16:22

Quote: Originally posted by pjig

Have to ask, but is the bp necessary to get the det train enough temp to get going , or is ematch, or the heat of 1/4” time fuse enough to ensure 100%ignition ?

BP may be enough to decompose and allow for a fast DDT of an ETN segment but it’d be too unreliable to leave it to chance. Time fuse and/or E-match directly on an ETN charge would be even more unreliable.

A good primary (adjacent to a time fuse or E-match), even in small (<10mg) amounts can help tremendously to sensitize the ETN ignition charge and ensure a proper DDT to move along the detonator train. If you’re unable/don’t want to prepare 5-nitrotetrazoles, NAP or SADS should work.

[Edited on 22-8-2024 by dettoo456]

[Edited on 22-8-2024 by dettoo456]

pjig - 22-8-2024 at 21:49

Copy that. I was just trying to make sense of why Bp serves any purpose in a det cap. Assuming a 50/50 primary and etn is the 1st segment, I can se it will raise Temps to hot spot the mix to det. But there is so many other hotter comps to serve this function.

I agree on the standard det train . Primary over secondary.

Some pack 1st a primary,followed by a 2nd segment as the primary/secondary 50/50 then base charge . I assume this is for weaker primaries, or secondary that need help getting going. Such as a sleepy base (less sensitive).
Teterazoles seem like another rabbit hole to venture.

[Edited on 23-8-2024 by pjig]

fx-991ex - 23-8-2024 at 05:51

The BP is mostly some kind of flame catcher, to make sure everything ignite correctly.

ManyInterests - 24-8-2024 at 05:44

I assume BP means black powder? Would using a simple safety match with nichrome wire wrapped over it also suffice?

Quote:

Some pack 1st a primary,followed by a 2nd segment as the primary/secondary 50/50 then base charge . I assume this is for weaker primaries, or secondary that need help getting going. Such as a sleepy base (less sensitive).

I do believe we have LL to thank for the 50/50 charge since I have never seen it before he mentioned it to me. For NHN and ETN it seems like a such a winning combination that I wouldn't bother with any other primary mixture unless I was simply experimenting with it for fun (like DDNP and mercury fulminate, which I plan on making anyway).

But as a general rule, this has been the case, a lightly pressed primary over a more strongly pressed secondary, for a very long time. I am not sure, but I think even old 19th and early 20th century detonators that just used a mixture of mercury fulminate and potassium chlorate, probably had two segments that were pressed at different densities.

For me I am still really excited to see how my bottomless (but double taped) detonators will behave. LL recommended that and I only have seen him use aluminum foil bottomed ones.

Laboratory of Liptakov - 24-8-2024 at 10:34

Bottomless detonators are used on first page in thread LL8 from Dr. Liptakov.
http://www.sciencemadness.org/talk/files.php?pid=669793&...
Left white, has output segment from pure high pressed ETN. Test runned without any tape. Next is Cu8, next CHP. All pressed on high density, tape was removed after pressing.
On seconds sides is see pressed black powder used a like plug for electric wire.... :cool:

ManyInterests - 25-8-2024 at 04:39

Ahh, I didn't look at earlier posts. I might as well read the whole thread again since it has been a while. (someone once mentioned to me that I needed to press the primary only lightly years ago, but I had forgotten...)

And I am very glad that they perform super well on such thick metal. I hope my ETN detonators do that on my next trip.... I also hope that I didn't add too much aluminum foil, since it could take some 5mm of space at the bottom. In some caps it isn't 100% blocked a few solid smacks (when not against a surface of course) could push the foil out, but I guess that still means it is good enough? The bottomless ones with double tape I am not worried about since I am pretty sure that the tape will not impede the explosive train that much.

My other question: When you made bottomless caps, was there anything you did to keep the energetic material from not falling out? Is simply putting the cap against a surface, loading it, and then pressing enough to hold it in place or what?

Laboratory of Liptakov - 25-8-2024 at 08:01

My other question: When you made bottomless caps, was there anything you did to keep the energetic material from not falling out? Is simply putting the cap against a surface, loading it, and then pressing enough to hold it in place or what?....Yes....
Material hold in the open cavity automaticaly and itself. Because is high pressed, arise solid the ingot. Yes, at open design is possible use nitrocellulose laquer, which create 0,05 - 0,1 mm layer. After drying.... :cool:

[Edited on 25-8-2024 by Laboratory of Liptakov]

ManyInterests - 25-8-2024 at 14:45

So as I mentioned, maybe I added too much aluminum foil that took up around 5mm of space. Too much or am I worrying too much?

Sir_Gawain - 25-8-2024 at 15:01

Quote: Originally posted by ManyInterests

So as I mentioned, maybe I added too much aluminum foil that took up around 5mm of space. Too much or am I worrying too much?

Yeah, 5 mm is way too much. You need more like 0.5 mm.

ManyInterests - 25-8-2024 at 15:35

Quote: Originally posted by Sir_Gawain

Quote: Originally posted by ManyInterests

So as I mentioned, maybe I added too much aluminum foil that took up around 5mm of space. Too much or am I worrying too much?

Yeah, 5 mm is way too much. You need more like 0.5 mm.

OK good, since I didn't load any of the caps I will take out the foil and add less. Good thing I waited since otherwise I would have wasted more material.

I did make one aluminum cap, around 70mm overall length and only taped at the end. I loaded 1.13g of ETN and 0.34 of primary mixture and it was barely half full. I don't intend on putting that one against a test plate, but I just want to detonate it while it is lying there, just to see how does.

for using nitrocellulose lacquer. I have NC spray (oxford brand), I might give it a go, but I am content with simple electrical tape.

pjig - 27-8-2024 at 21:01

The only loss you would have experienced ( with too big of a base plug)would be energy lost at base of cap. Side walls transmitting the det energy laterally. Only an issue in shape charges needing needing energy focused on a conical point to maximize efficiency for a focal point of energy o punch holes. If the focus of the cap is for initiating general charges, then no big deal.

ManyInterests - 30-8-2024 at 15:42

Quote: Originally posted by pjig

The only loss you would have experienced ( with too big of a base plug)would be energy lost at base of cap. Side walls transmitting the det energy laterally. Only an issue in shape charges needing needing energy focused on a conical point to maximize efficiency for a focal point of energy o punch holes. If the focus of the cap is for initiating general charges, then no big deal.

My aim is still to make as efficient a detonator as I can. It is a personal goal. I did notice that laterally my caps did a great job. They blew the sides of the fence bracket apart on a very consistent basis, but I am concerned about one thing regarding brass cartridges. If you look at my images, you'll see they did a lot less lateral damage than the steel ones. While the brass cases obvious had a much tougher bottom (something which I will remedy next time by drill a hole through the bottom and having the explosive train start from there) the sides should have still given enough confinement for a full DDT and blown that apart, too.

Or are the steel cases simply that much better?

edit: I hope the aluminum caps I am trying out won't fail like that. Most commercial and military caps are made of aluminum after all.

[Edited on 31-8-2024 by ManyInterests]

pjig - 30-8-2024 at 19:38

Yes commercial caps are aluminum. It’s an alloy, but one close enough source is spent or 2nd hand arrow shafts . If you know an archery club or some avid shooters, those al shafts are very good cap bodies. The steel I’m sure is better for confinement, but, If your det train is hot , it’s not needed. I do like the aluminum ball approach for a base plug. The use of epoxy type materials created too thick of a plug . The aluminum ball can be sealed with super glue if desired after hammering into place.

[Edited on 31-8-2024 by pjig]

ManyInterests - 31-8-2024 at 07:24

Quote: Originally posted by pjig

Yes commercial caps are aluminum. It’s an alloy, but one close enough source is spent or 2nd hand arrow shafts . If you know an archery club or some avid shooters, those al shafts are very good cap bodies. The steel I’m sure is better for confinement, but, If your det train is hot , it’s not needed. I do like the aluminum ball approach for a base plug. The use of epoxy type materials created too thick of a plug . The aluminum ball can be sealed with super glue if desired after hammering into place.

[Edited on 31-8-2024 by pjig]

So adding a dab of super glue on the end will seal it? Sounds good.

For aluminum tubes. I can get fresh arrow shafts that are 7mm OD and 6mm ID, but what about the aluminum tubes that you can buy from aliexpress or Amazon? The obes I got to test are 8mm OD and 7mm ID giving them more space for larger charges. But they are very soft and easily malleable. I thought of getting thinner ones but I think they would be too thin at that point.

pjig - 31-8-2024 at 09:32

The arrow shafts tend to be larger dia. This is better for a couple reasons . The alloy is harder aluminum, the dia allows electric match to fit in the hole, and the charge is able to pack lower in the tube allowing less length cap body needed. Skinny tubes fill up quickly.

UndermineBriarEverglade - 5-9-2024 at 13:47

Quote: Originally posted by UndermineBriarEverglade

Yeah terribly low density. The small (rapid pour) acetone-formed crystals are very fluffy even when pressed hard. 500mg sounds good, I will melt cast a thin layer and then crumble it up to make the output segment.

450mg ETN output segment: melt-cast, then crumbled to fit into cap, then pressed. 11.55mm height x 6mm inner diameter tube = 1.38 g/cm³

50mg loose crystals on top for EBW

Setup of cap on the 1mm plate was the same as before. The hole from the bottom of the cap is not much larger than before. But a large hole was created at the side. Looks like the plate was pulled apart. Popped the lid off my bucket of cat litter!

ManyInterests - 5-9-2024 at 16:22

https://youtu.be/2hT9GQ74Rnk

So I just watched this video and it answered quite a lot of inquiries I had about detonators, and It really got me thinking about a lot of stuff. Like with regards to e-matches, he uses professionally made ones, but the examples of his homemade stuff just seem lack luster. With my NHN I use a nichrome wire that is over a safety match to provide a fairly decent flame that I do believe has been sufficient to set off my detonators, so I will continue to use it as is.

But what he did mention about things like reinforced detonators, which is a term I heard before but was unsure as to how it looked like. I also did see how he used an arbor press to REALLY press his ETN hard into the cap.

I will never do that and I will stick to hand pressing as I always did, but it did make me think. Since he used multi-stage pressing, with the bottom most layer being the most hard pressed, with the 2nd half more lightly pressed, and maybe topped off with a more tamped amount of ETN before the tamped primary mixture.

I haven't loaded any of my detonators for the next test, since my next test is mostly about how bottomless (but taped) will fare vs. aluminum ball + taped caps. I think that is a good thing to add to the experiment.

Laboratory of Liptakov - 6-9-2024 at 04:30

Small parts from output side of detonator show on full detonation ETN. Your EBW look reliable...... :cool:

...Good work

ManyInterests - 9-9-2024 at 11:42

I thought of something. Since brisance is a very important part of the energetics used in detonators I wonder if I should try a new mixture.

According to Wikipedia a 50:50 mixture of melt-cast ETN and PETN by weight makes for an extremely brisant explosive, with a VoD of close to 9,000 meters per second. Since I do have some PETN (recystalized once) I want to try it out.

My one question is this: should I just mix the powders together or should I try to melt the ETN with the PETN? I saw one of Dugan Boomfax's videos where this was done. I assume the latter would be better since it would mesh the two materials together better. But I have been wrong in the past.

What do you guys think?

Sir_Gawain - 9-9-2024 at 14:13

50/50? Shouldn't it be 66/34 ETN/PETN for oxygen balancing?

[Edited on 9-9-2024 by Sir_Gawain]

ManyInterests - 9-9-2024 at 15:21

Quote: Originally posted by Sir_Gawain

50/50? Shouldn't it be 66/34 ETN/PETN for oxygen balancing?

[Edited on 9-9-2024 by Sir_Gawain]

I quoted wikipedia's article on ETN. As quoted below

Quote:

Mixtures of melt-cast ETN with PETN (about 50:50% by weight) are about the most brisant explosives that can be produced by moderately equipped amateurs. These mixtures have Pcj slightly above 300 kbar and detonation velocity above 8 km/s. This is close to the maximum of fielded military explosives like LX-10 or EDC-29 (about 370 kbar and close to 9 km/s)

I did notice that there are no citations for this statement. I also reviewed Dugan Boomfax's video on ETN where he does cite a 65:35 ratio of ETN

ETN and he DOES melt-cast them together and grind them up afterward. In this situation I believe you are correct. A greater ratio of ETN would be more desirable in this case.

So this is what I will do. I will melt-cast ETN and PETN together in that ratio and grind up as finely as I can (with all safety considerations obviously...) and I will use that to load up my blasting caps for my next test.

And for the loading, I will load up the first 50% of the cap with hard hand pressing before more lightly pressing the rest. Gotta get that explosive train going!

UndermineBriarEverglade - 3-10-2024 at 07:11

ManyInterests, if you are making 10 caps at a time I would actually recommend NOT to use melt-cast ETN. In August I made some ETN, neutralized with baking soda, recrystallized several times with acetone, and crashed into urea solution. I stored melt-cast fragments to use for output stages and fluffy crystals to use for initiation, both at room temperature. Recently the melt-cast fragments began to decompose and release significant red NO2. Thankfully I caught it in time. The original crystals haven't decomposed at all. I think that heating accelerated decomposition. Scary to think of 10 confined ETN samples fuming where you can't see them.

[Edited on 2024-10-3 by UndermineBriarEverglade]

ManyInterests - 13-10-2024 at 12:45

OK... so my trip was informative, but also kinda disappointing.

I actually made... 20 detonators! Yeah, I was going really hardcore with this and I was hoping to get enough information to say that I know how to make a good detonator and call it a day. But I had some surprises.

I made detonators using aluminum bodies (6063 aluminum alloy), 5.56x45mm shell casings and 7.62x39mm shell casings, and 304 steel tubes with the ends cut off.

For the brass bodies, I had pushed out the spent primer and drilled as wide a hole as I could in the bottom and loaded it to go from the hardest point to the mouth. Thus learning from my previous mistake of thinking that I can just load it from the top and call it a day.

I made two variants of all my caps. Half had aluminum foil plugs (very thin 0.5-1mm plugs at the most) and then added a little tape to waterproof it, and the other half only had tape at the end to waterproof it and prevent any energetics from crumbling out.

I loaded the caps as follows: First half the melt-cast ETN was loaded and pressed as hard as I could by hand, followed by the second half with decent pressing but not as hard as the first. Then around 0.32g of 1:1 melt-cast ETN:NHN mix primary was added on top and only gently tamped without any strong pressing (less than 1kg pressure). For 12 of the caps, I used around 1.14g of ETN in the caps.

6 caps (2 aluminum, 2 steel, and 2 brass, again with half having foil and the other half only tape) were loaded with 1.05g of 65:35 ETN/PETN melt-cast together. The primary loading is the same as above

I also made 2 100mm caps that had around 3.25g of melt-cast ETN and 0.4g of the same primary mixture. These were extremely powerful and practically obliterated large parts of the witness plate.

So I only posted pictures of the steel caps. Because one thing that I found is that the aluminum caps did not appear to have any effect on the witness plate. In fact, it was almost like I was using my old plastic cap bodies for them. The brass caps also didn't perform well at all, merely bending the side of the fence bracket (that is what I am using for a witness plate). This was the case across the board for all the energetic materials I was using, whether it is ETN or ETN: PETN mix.

The steel caps, however, performed excellently. As LL says, he uses thicker steel bodies than I do, but mostly bottomless, and he has produced great results.

The bottomless steel caps with ETN did better than the ones with aluminum plugs. The ones with the PETN loading did almost equally as well regardless of the aluminum plug or just tape.

However there is the question as to why the others failed to fully detonate. I watched Dugan Boomfax's video on detonators and one thing that he did mention that when the output fails to fully detonate it means that there could have been insufficient primary to set it off, or that it does need to be pressed more (the primary that is).

Or the alternative is that the NHN is simply not as good of an initiating agent as I thought. While it with a steel body it appears to be good enough, I am wondering if I should experiment with other primaries, like iNAP. I am very accustomed to working with the fairly safe NHN, but I think iNAP can be made safe to work with, especially if it is loaded as gently and tamped as gently as I do with the NHN.

[Edited on 13-10-2024 by ManyInterests]

[Edited on 13-10-2024 by ManyInterests]

Sir_Gawain - 13-10-2024 at 13:26

I think your problem might be with the ETN/NHN mixture. I’ve used pure NHN with great success (~200mg per detonator). I think the ETN just slows down the burn rate, preventing it from undergoing DDT.

ManyInterests - 13-10-2024 at 14:59

Quote: Originally posted by Sir_Gawain

I think your problem might be with the ETN/NHN mixture. I’ve used pure NHN with great success (~200mg per detonator). I think the ETN just slows down the burn rate, preventing it from undergoing DDT.

Yes, I will revert to using only NHN and not the mixture that LL recommended.

BTW, there is an earlier thread of a spiked NHN with sodium chlorate that the maker said was very effective, what do you think of that?

ManyInterests - 16-10-2024 at 08:01

Actually on second thought, I think LL's mixture is fine, Or maybe make caps with one pure nhn and the other mix to have a direct comparison. I just need a more robust primary for the other cap types. I will try uNAP and see if it is able to make stuff in plastic or aluminum bodies go off.

One other thing I would want to do is to load brass caps from the top, as I did previously, but obviously have the bottoms fully drilled out as wide as I can and just tape added. This is because looking at the latest stuff it seems like like the older ones with thr ends still on did better... it makes me wonder how the bottomless ones would perform.

I will make another eight caps (four steel and four brass) for testing. Moderate pressing on all the ETN, with half having 0.3g of pure nhn and the other around the same of an nhn etn mix.

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