So I decided to clean out my pellet trap...

[1216bandit]

The most I ever got out of my rubber mulch type trap was just under 10 lbs!  I have to make another one...I used 2x10's which I had on hand, with 1/8 steel back plate and the dang thing is quite heavy when you add the mulch...I do shoot my .22lr at it with no issues.

[Back_Roads]

 I notice the pellets seem fairly intact from the rubber mulch trap, compared to other trap materials I have used. So i am assuming the small particles of lead are minimal.

[Rallyshark]

I agree.  The rubber mulch seems to keep the pellets in tact for the most part.  There are some shavings and pieces from when pellets hit pellets in there, but I don't worry about it too much.  I mean, this is something we may be cleaning out once in a few months, so I think the exposure is minimal.  I've probably gotten far more exposure from fishing, and loading .22 bullets in my my ruger 10/22s in my lifetime

[Underdog]

I just made mine. It's similar to the one displayed with a few differences. I didn't think about hinging the front or making it out of plywood. I did use a slide-in 1/4" MDF backing plate to contain the mulch. I calculated the cubic inches of the bag of mulch and made my box accordingly. I made it smaller, and it's a good thing I did, because I almost didn't have enough mulch.
I like the idea of using the styrofoam squares. I bet they're more quiet than the MDF.
But I love it. It makes shooting much more mobile. Better than a fixed target any day!

[Back_Roads]

 I had some 1" pink insulating foam full sheet and a partial , I squared them off in 2' sections and shrink wrapped them together about 1 foot thick, I use that as a trap for chrony testing my springers go in about 4 - 6" but my .177 at44pa shooting a Eun Jin .177 Cal, 16.1 Grains, Round Nose , almost made it all the way through, i'm sure its stopping life is limited , but have steel padded with wood as the final backstop.