need advice on building rimfire backstop for home range

[tionico]

Have some acreage and am wanting to build a backstop that wil STOP rimfire rounds at 25 yard sdistance. Thinking of uprights, then two by lumber in two layers, with sand or small grain gravel 9chipped, rather than round) to fill the space between.

My question:

HOW THICK does that gravel need to be to absolutely STOP the rounds from exiting out the back? No space to build an earth bern. I can work out the hight and width, but the thickness of the gravel "wall" is something I'm needing to know. HOW much gravel thinckness is CERTAIN to stop any rounds from exiting out the back?

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[AMT]

Quick Google-fu..... the first response sounds very reasonable to me:

.22 Backstop thickness?

www.rugertalk.com

"....Using sand is a very good bullet stop. Think about the sand bags soldiers used during the war and they were used to stop much more powerful rounds than .22lr.

You can take 2x6 boards and make a frame to hold the sand for the backstop. Google it and you will see 2x6 frames with drywall sheeting to hold the sand in was stopping 9, 40, and 45 ammo rounds. That was only six inches thickness of sand.

Make two of these frames and put back to back and you should not have any handgun bullets penetrating through. More than likely the no bullets will get through the first frame. I found using truck mud flaps instead of wood or drywall worked much better. The bullets go through the flaps but then the holes close back up some. This worked well for keeping the sand in place in the frame.

I am shooting into 1.5 yards of sand with 4x6 oak planks backstop. I have not had any bullets going through or out of this backstop. I have used 30-30, 22lr, 9mm,40, and 45 with no problems."

 

[North Plains]

Sand works well. I built one 24" deep. It stopped everything I ever shot at it.