How much rubber mulch to stop pellets?

I've built at least 4 pellet traps of different designs. The first one basically copied the plastic Crosman trap my kids gave me. I used the metal back of that trap and put it in a wooden box. I sloped the back and filled it with mulch. It worked but I occasionally hit the 3/4 plywood sides of the trap and eventually it was pretty well ruined. Next I made one out of an old electrical box I found in my shed. It is made of heavy gauge metal, I estimate 16 gauge. The back bulged out some but it is still usable. But the back bulging told me it's less than 3 inch depth was insufficient for my guns. So I made one of 3/4 plywood that is 6.75 inches deep. I put a metal back inside the plywood one too. It is sufficient for even my 50 fpe 25 caliber. I never have heard pellets hitting the metal back.

But it is somewhat heavy so I made one that is only 5.25 inches deep of mulch. I shot it yesterday with my 25 caliber Avenger tuned to shoot FX 25.4s a little under 900 fps. About 43 fpe. I'll include a picture of what happened. I heard the pellets hitting the metal back which is inside the trap protecting the plywood back. This trap is made of 1/2 inch plywood (mainly). I pushed some glue into the crack and clamped it up, it is drying in my shop right now. So 5.25 inches of mulch is not enough for a low 40s fpe airgun. The only time I have hit the back before this was shortly after I made it when the mulch sagged down. I took the cardboard off and put in a bit more mulch and no longer hit the back with my low 30s fpe 22 caliber airguns.

So if you shoot airguns 30 fpe or below, about 5.25 inches of mulch is sufficient in your trap. If you shoot 50 fpe airguns or less, 6.75 inches will work. Possibly a little less.

Both my recently built traps have 1/8th inch thick steel clamping the cardboard and target in place and protecting the 3/4 softwood frame around the opening and the plywood sides. The 1/8th steel shrugs off impacts of even my 50 fpe 25 caliber. It's the only thing I had to buy for the traps but I think incorporating it was well worth it. I put softwood around the opening to hold the drywall screws holding the metal, cardboard, and target on (if I screw directly ito the plywood it splits).

5.25 inch trap.jpg
 
I use Rubbermaid 7 gal rectangular trash cans with a depth of 10.5". These filled with rubber mulch stop everything I have shot at them from .177 to .30, at both 25 and 50 yard distances.

I don't know whether it makes any difference in stopping pellet penetration, but I only use the Rubbermaid products as the plastic is softer/less brittle. These take more shots before needing replacement than other cheap China made plastic trash cans, where the pellet breaks its way through the brittle plastic, instead of pushing its way through the flexible plastic (if that description makes any sense).
 
Lining a trap with pavers in the back is a solid idea but they are not indistructable. I have them behind my "know your limits" swinging target and even my fairly modest sized airguns are close to shooting through them after a bunch of hits. So I flipped them over. But if you slow the pellet down with the mulch it should minimize any damage to the concrete.
 
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I agree with the 6 inches initially? But after a few thousand rounds, you will go through that quite easily with anything over 30 fPE especially if you’re shooting groups it will bore a hole and go significantly deeper! So just be aware I would not shoot 6 inches more than a couple of times in the same spot. I like 14 inches with a hard backstop in the back of the container or box and yes, you will hear it hit that sometimes👍🏻 Great post
 
This is the front view of my trap. The steel is 1/4 inch wider than the plywood sides of the box. That is to minimize the possibility the projectile hits the plywood side. Behind the steel is cardboard. The top and bottom metal pieces clamp the target in place. What I really like about this trap is I can use it a lot without having to buy anything like a replacement lid. I cut the cardboard from boxes delivered to my house. The mulch seems to last if not forever a really long time. I've taken 10lbs of pounds of pellets out of my traps and reused the mulch each time. Without the steel I used to eventually shoot the plywood box to pieces but with the steel that doesn't happen. I only hit the steel when I'm doing something like sighting in a scope but I do hit it occasionally.

Pellets do not really damage the mulch from what I can tell. Occasionally one sticks to the mulch but the mulch doesn't get torn up. I have to add mulch some after replacing the cardboard especially on a new trap. But I am pretty sure that is due to the cardboard bulging out in the center allowing the mulch to settle. This trap has had several thousand rounds shot into it so far. I added mulch one time. I use this trap with my under 20 fpe airguns but more often with my slightly over 30 fpe airguns. Works great.

Trap front.jpg
 
Make sure you shake the mulch down to get it to settle as much as possible and then top it up again. to get the container full. If you don't you will have a gap at the top and the pellet will go thru your container and the drywall behind it in the basement. Then you need to have something handy to cover the holes before the wife comes down.
 
A good “insurance” backstop is a piece of used conveyor belt. You can buy strips on Amazon. It’s basically 1/4” rubber with layers of steel mesh. It stops 80fpe 44gr .30 diabolo shaped pellets cold.

I’ve used the rubber mulch in a wine carry box 10”x8” and only get pass thrus after pounding the same location ( pellet on pellet ) multiple times. A 4”x12” strip of conveyor belt behind the mulch stops everything I’ve thrown at it.
 
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I have found some cheap rubber tiles i want to try in a pellet trap, they are 40 X 40 CM and 30 mm thick.

Not yet sure how i will deploy them, as is i am sure holes would get drilled in them sooner or later, so i am thinking hang them off the top of the trap so they can also flex a little to dissipate impact.

This is for outside use, so no problem with pass thrus if it should happen, but i would like to catch as much lead as possible.
 
Maybe if you attached the tiles with surgical tubing or bungee cord at the corners?
Thats a good idea, i was just thinking of attaching it at the top, but then hitting at the top it would not be able to flex very much there.
Some inner tube i think should do the trick.

Mind you that mean i will have to make the box itself a bit larger, but that is not going to be a problem.
I could also make the box taller and have the rubber tile on a extension of some sort, that would mean hitting the top of the tile it would still be offset some from where it is attached / hinged and so able to swing back.

I could also have the rubber tile attached to a bar, that then rest on a slide in either side, with a slight incline on it, that would mean when i hit it, it would be pushed back and up a little, only to slide back down again.

Suddenly my mind is a raging torrent of ideas.
 
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I used a 14 gallon plastic tub 14in deep. Not even my 150fpe .50 cal will punch through that.

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It may. I had some bullets from my Sam Yang Dragon Claw punch all the way through a 5 gallon bucket packed with rubber mulch from top to bottom. I would shoot it laying on its side with targets stapled to the top. I had a hay barn behind it to catch strays, but would rather not shoot too many holes in that.
 
I use one of the black storage containers from Costco/HD/Lowes with the yellow lid. Not sure the size but I'll include a pic below. I then place 3 bags of rubber mulch into the container, one on top of the other. I don't open the bags up and the length and width seem to fit perfectly and the height of 3 bags brings it right near the top.

I have shot everything from 30 fpe up to my Slayer 357 into this and nothing has ever made it past the second bag. Just to be sure though I have some backing behind it which is a 1/2" piece of plywood with about 4 layers of ballistic fabric (this stuff: https://www.amazon.com/gp/product/B00I80KV1W) which by itself 4 layers will stop a 18gr 22 pellet at 30fpe. Behind that is a 1ft concrete house foundation.

INdoor Target - 1.jpeg
 
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