Vacuum pipe, and a couple of old bed sheets. A local retailer built one for test-firing, and it caught all the BBs, even from a Tanaka M700. Cost maybe $30 to build, and was 6' x 6' x 4' deep. Smaller would be cheaper and very lightweight, only a few pounds at most.

"Sticky" BB Target

can be wall mounted or just left standing on anything.
Many can take a good shot from an upgraded AEG as the gel material is very good.

Had one too, cracked through with my 380 FPS SPR.
Also, not very good with full auto from BB's flying everywhere. lol

Hahahah, Pete, I didn't know you were such a plinker.

I just use a soft and thick pillow to shoot at and catch my BB's, nothing too advanced but it works, and I have always put them back in my gun and re-used them, so far not a single jam while using the "spent" BB's.

Well, it's a combination of boredom and coming home from games with un-used locaps......I don't like leaving them loaded and I can't be bothered trying to get them back in the baggie.....so I blast them out.

I've built one. Its actually just a cardboard box with a hole cut out on one side. Inside is a string that runs from left to right near the top. I fold a portion of a paper target and then hang it on the string and is held in place with a paperclip. Behind it i use a durable piece of cloth that prevents the bb's from penetrating the back side of the box.

G'day,
 

Plastic pail with a lid. Cut out the lid so you have just the lip that goes over the sides. Put carpet or old towel or pillow or whatever in the bottom. Use the lid to hold the target on. The energy is absorbed by the padding and the BBs roll down to the bottom where they don't get smashed into by other BBs. I use cat litter pails, which are square. Works great and now I have a few hundred thousand BBs for grenades and mine loading. {: