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Penetration is one measure but transfer of energy is another. A projectile that exits a animal wastes all that excess energy. A great bullet would expend all its energy inside the animal and come to rest against the inner hide on the opposite side. Some will say a exit hole allows faster blood loss, but the bleeding will continue internally at the same rate depriving organs of blood flow.
The cavity in the clay from the HP bullet was impressive. Another good vid.
Take the "oil filter" and submerge it in water for 2 min. Pull it out and let excess water drain for a few minutes. Now shoot the same load with the "wet" filter and compare the decibel levels.
Even though the camera didn't pic up an image of spark, it may have occurred. A heavy rubber band (cut up old bicycle tire tube) could hold open the gas without having to wrap it around several times: allowing plenty of shooting time and a gas rich environment. A box with a cut out to sight an shoot through would also help contain the gas for a bigger pop if you get a spark.
Good luck my friend.
Milla Jovovich was prettier when she did it. Lol.
You have to be carefull inserting the tube /shell as the shell appears to free fall some distance which could cause it to discharge. That design requires a solid impact to fire. If the base was drilled a few inches above the firing pin and a short tooth pic inserted to hold the tube/shell well above the firing pin: then only the force necessary to break the tooth pick would allow a solid force and gravity strike on the primer. This would be much more sensitive. This is for informational purposes only as such devices are prohibited/illegal for civilian use in most jurisdictions. Interesting topic.