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briandg · February 3, 2018, 11:24 AM

a rubber backstop as spoken would have been a literal backstop, with a steel plate and pit full of shredded tire. The secondary backstop was a set of large sheets of what is essentially tire material, black tire rubber laminated with threads of some sort, possibly fiberglass in many brands, but some use plain thread.

This is just a backstop intended to stop or catch as much backscatter as is possible, there must be a steel plate behind with a pit to catch bullets.

Tracer rounds are hot. Very hot. They are a metal mixed with a binder, an oxidizer, and an element that will add color to the flame. The metal is generally magnesium, I don't remember what the oxidizer is. Magnesium burns very hot and brightly. the binder prevents this oxygen fed fuel from blowing off instantaneously like a flash bulb. the colorant, likely strontium, burns along with the magnesium.

A tracer is essentially no different than a firework rocket or the stars from them. Black powder or another material. the powder is treated with a retardant. magnesium or aluminum are added to burn it brighter. There are many different metallic salts that either in a combination or alone burn off with the high temperature magnesium to add colored light to the hot white light of the magnesium. Sometimes plain iron is added to the flare for color.

So, a tracer intended to reach out for hundreds of rounds was discharged in a single pit, blasting extremely hot gasses into a pit/pile of easily ignited rubber shreds. Then, you have a tire fire. There are other types of steel backstops. a standard angled sheet of steel deflects the bullet downward into a spiral shaped tube. the round tube forces to bullet to run round in a circle and expend its energy as friction. as bullets pile up, there is no need for the thing to spiral around the steel, it's just locked in place and the impact energy is expended against the piled bullets instead of the steel snail as friction.

A truly high tech range like the nra has at one of their facilities has a continuous oil feeder that lubricates the steel. It is obviously a non-flammable oil such as glycols or silicones, something that would be able to withstand the high heat of friction and resist sparking from any steel particles that hit it. The oil's purpose is to reduce friction heat, prevent some lead buildup, and to capture any sparks that are caused by bullets on occasion.

February 3, 2018, 11:24 AM	#32
briandg Senior Member Join Date: May 4, 2010 Posts: 5,468	a rubber backstop as spoken would have been a literal backstop, with a steel plate and pit full of shredded tire. The secondary backstop was a set of large sheets of what is essentially tire material, black tire rubber laminated with threads of some sort, possibly fiberglass in many brands, but some use plain thread. This is just a backstop intended to stop or catch as much backscatter as is possible, there must be a steel plate behind with a pit to catch bullets. Tracer rounds are hot. Very hot. They are a metal mixed with a binder, an oxidizer, and an element that will add color to the flame. The metal is generally magnesium, I don't remember what the oxidizer is. Magnesium burns very hot and brightly. the binder prevents this oxygen fed fuel from blowing off instantaneously like a flash bulb. the colorant, likely strontium, burns along with the magnesium. A tracer is essentially no different than a firework rocket or the stars from them. Black powder or another material. the powder is treated with a retardant. magnesium or aluminum are added to burn it brighter. There are many different metallic salts that either in a combination or alone burn off with the high temperature magnesium to add colored light to the hot white light of the magnesium. Sometimes plain iron is added to the flare for color. So, a tracer intended to reach out for hundreds of rounds was discharged in a single pit, blasting extremely hot gasses into a pit/pile of easily ignited rubber shreds. Then, you have a tire fire. There are other types of steel backstops. a standard angled sheet of steel deflects the bullet downward into a spiral shaped tube. the round tube forces to bullet to run round in a circle and expend its energy as friction. as bullets pile up, there is no need for the thing to spiral around the steel, it's just locked in place and the impact energy is expended against the piled bullets instead of the steel snail as friction. A truly high tech range like the nra has at one of their facilities has a continuous oil feeder that lubricates the steel. It is obviously a non-flammable oil such as glycols or silicones, something that would be able to withstand the high heat of friction and resist sparking from any steel particles that hit it. The oil's purpose is to reduce friction heat, prevent some lead buildup, and to capture any sparks that are caused by bullets on occasion. __________________ None.