TL;DR

Recently got a box filled with cloth as pellet trap. ~200 pellet in and looking good.

Longer version:

I have been using a box filled with wood mulch for the pallet trap since beginning but always looking for some rubber mulch which I believe more reliable and quieter. Couldn't find any tho.

Until recently I got some old cloths from kids for painting job (too dirty or too damaged to give away or donate), I found they could perfectly firmly fill up a big cardboard box from PnS and seemed to be not bad as pellet trap and gave it a go.

Now it has been a few weeks and about 200 pellet in and looks pretty promising. Much quieter than the wood mulch. I hope it is easy to maintain - just take the clothes to another box when the front cant hold paper anymore. Can hear some pellets on the bottom of the box.

Wonder if anyone tried this method before.

Btw, I still got the box of mulch on the back of the cloth trap and 15mm wood board and a 2.5mm steel panel on the back ;)

Can post some pics when it is working.

I guess you could in theory shake out the lead later.

I made one a while back before I got around to making a 'proper' trap.  Very simple to build and it worked very well, but I needed to replace the front portion with another layer as it was quickly shot to pieces allowing the garments to spill out.    

There were be pockets of pellets that fell out when I dismantled it, but a large portion of them were well entangled in the cloth and I felt it wasn't worth the time to recover them.  

Very effective, quiet and cheap.