Centerfire bullet trap

[MLC]

I want to set up a mobile backstop on my property.
There is the potential for agricultural use in the areas that I plan on using for shooting so I do not want to leave large deposits of lead in the soil.

My plan thus far is a box made with timber and plywood, packed with fine sand. I plan on building it onto an existing trailer chassis so I can move it with my tractor or truck.

Obviously, shooting something will leave bullet holes so I'm trying to figure out something to use as a resilient membrane on the face of the target to retain the sand and lead fragments.
I'm currently considering a sandwich of plywood, mattress foam, insulation board and homasote for the face of the backstop.
My estimation is that two 6" chambers of sand should be sufficient for receiving 22lr, 223, 223AI and 308 match and varmint bullets at 1-400 yards.

Has anyone completed a similar project or seen a rifle penetrate more than 6" of tamped dry sand?

 

[LHSmith]

I built backstop bunkers for our local club with 6x6 timbers on the sides and rear, 1/2" conveyor belting in front, and backed up the belting with old tires, then filled with sand. I found on long-range.com the military range design specs, and made our "depth" (front to back) 8'-0 due to some members who cart a 50 BMG cal. rifle to this range. I don't recall the recommended depths for the various calibers, I will try to find my file and post the numbers. 6" is way too minimal, I believe the .223 w/ std ball was ~ 25", the .308 w/ std. ball was ~ 35", the 50 BMG was 50", armor piercing ammo required even more depth. I'm sure the mil spec has plenty of safety factor built in, but in my clubs case I added extra depth for liability reasons.
The belting works well, except for the 25 yard target bunker due to very high volume of pistol use. I put belting patches over the holes. In the near future I plan to remove the first two feet of sand and replace it with shredded rubber.

 

[LHSmith]

Also, there is a dramatic difference in penetration between damp sand and dry sand, if you can keep the sand dry you can reduce the backstop depth by almost 1/2.

 

[LHSmith]

Google DA Pam 385-63 , go to table 6.1
These are the following recommended backstop depths: .223 dry sand = 17", wet sand = 21", .308 dry= 20", wet = 36", 50 cal. dry = 32", wet = 50"
As I said before there has got to be a considerable safety factor built into these numbers, but I am sure 6" won't suffice.

 

[wapiti25]

I would try a steel plate set at 45 degrees to deflect the bullet down into your sand. The steel should be armour plate if you can aford it. The shalower the impact angle makes the bullet want to slip off instead off penetrating. Even if you don't use steel you can set the back stop at an angle which makes it look thicker to the bullet. good luck

 

[effendude]

My club did some quasi-scientific tests regarding centerfire bullet penetrations when we were reviewing the 50BMG. My findings were similar to LHSmith's.

We packed 55 gal. plastic drums with moist, fine sand (our native soil and berm material) with a layer of cardboard as a cap and at each of the two ribs of the barrel to better judge penetration. We shot .223 55gr FMJ, .308 Win. 147gr FMJ and .50BMG Ball at 100 yards. The penetration of both the .308 and .50 were similar. Both bullets shed their jackets and then drifted off the path and stopped before exiting the barrel. Most only made it 20-25". The .223 was a non-factor with about 12" of pentration. I'm sure armor- piercing would go farther. Our club found it simpler to restrict the .50BMG to ball ammo only. As a side note, bullets like a Barnes go way deeper than a FMJ as they don't shed themselves apart.
Scott

 

[MLC]

Thanks for your input.
My plan is to have the sand as protected from rain as possible.
This is an interesting test I found while searching for data on the thickness of sand required to stop bullets.
http://www.theboxotruth.com/docs/bot7.htm

 

[LHSmith]

Keep in mind, that once the initial backer material is compromised, shots through the same hole will penetrate deeper due to the bullet retaining it's integrity ( nothing to promote initial upset), and also depending how damp the sand is a "tunneling" effect would enable even deeper penetration.

 

[jo191145]

On my home range I use the biggest darn tree trunk I can find for a stop. Preferably laid down to shoot with the grain. They last for many 1000's of rounds. More than any plywood box could ever hope for.
The only downside is the weight. My current one is roughly a 40" diameter pine trunk about 60" in length. Pretty hefty chunk of wood. For me they're stationary and free.

If you live in a part of the country where trees are not scarce you might consider it. Some arborists/loggers/landfills might have just the piece your looking for for free.

 

[mark454]

I used to work with a kid and he took an old chest type freezer filled with gravel for a backstop. It could be pushed or pulled with a tractor,or placed on your trailer. It would be simple and cheap. Just a suggestion.

 

[rogn]

The refrigerators fall apart in ayear or two,depending where ypu live, but it can easily be mounted on atrailer. Combinations of sand and gravel will stop most anything. The thin shell will falla part quickly. Heavylogs work wel with most hunting rounds, but fmjs tend to penetrate too much. I remember an experiment at an early age with a 7X57 and a 173 FMJ. A 25" hicory tree had axit hole not much bigger then the entance, but there a a 4' trench cut behind the and the bullet hadnt stopped. Expanding bullet are OK. The best ive found so far is as above, excpt we have 30 gallon plastic barrels, some are sun resistant and some arent. The walls hold up weel with only neat puncturs, I takes a few thousand pointed rifle bullets to wwar out the face of the barrel, but flat nosed such as 45 keith bullets wear the face out a lot faster. But then either repace it or cut the side out of another barrel and screw it in place. You kinda have to use 2 layers of barrels or fill the interbarrel space with a good log, because people do miss. We have 3 such set up at 440 yds. Thsi si across the horse pasture, and does Have a heavy berm behind it.Targets are set cnterd on the barrels Many thusand rifle rounds,mostly 22s, 6s, 6.5s 7s and 30s areused,. Barrels are not dry due to many holes nad requirerefilling from time to time. 30 cal fmjs and 223 fmjs are contolled, with no ecapees. No 50s allowed.

 

[I_shoot_for_fun]

You could build yourself something like this snail-type trap.

http://www.snailtraps.com/

 

[Kenny474]

I have a sand box backstop that I have been using for 3 years now, though it only sees 22LR. I used a couple layers of rubber roofing material on the face, and it seals up rather well. You can barely see the holes until you have put a few thousand rounds into the same spot, then I just replace it.