I had the opportunity yesterday to do a quickie field test of the Caldwell AR Brass catcher - it attaches using a single wide velcro strap and has a sturdy wire frame that covers the ejection port competely
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http://www.cabelas.com/product/Caldwell174-AR-15-Brass-Catcher/1170134.uts?Ntk=AllProducts&searchPath=%2Fcatalog%2Fsearch.cmd%3Fform_state%3DsearchForm%26N%3D0%26fsch%3Dtrue%26Ntk%3DAllProducts%26Ntt%3Dcaldwell%2Bbrass%2Bcatcher%26x%3D10%26y%3D6%26WTz_l%3DHeader%253BSearch-All%2BProducts&Ntt=caldwell+brass+catcher&WTz_l=Header%3BSearch-All+Products

The testing was conducted on my AR pistol (7.5" barrel) and 2 different M-4 style AR 16" rifles.

The product worked for us as advertised, NO glitches of any kind and all the brass was captured into the zipper-bottomed mesh sack. My brother and I had no problem with the unit holding at least 30 cases. We plan on reloading for these guns and this clever $15 item will make capturing the spent cases almost as easy as those from a revolver - VERY slick item,.

Link made hot and SHORTER.

LINK


I have had pretty good results with mine. I once had a stovepipe because the case hit the brass catcher and did not eject cleanly.

To be honest with you every catcher I have ever used, and I have used most of them, they have all had major flaws. For me personally, a 10x10 blue tarp placed on the ground where you are shooting is the best catcher you can use. Roll around, shoot from unusual positions and no issues, no jams, no stopping to clear jam, when you are done you simply drag each corner to the middle and dump into a 5 gal bucket. Sort while watching your favorite TV show.

Mine would shift and droop on the non-supported side constantly causing stovepipes and even missing brass at the end of a 30 round mag. It didn't matter how tight I got the velcro. It just didn't work well with the smooth round handguards..

I switched to the new model when they came out. I love it.
-The bag stays open instead of closing up when you get some weight in the bottom
-It doesn't sag or twist
-It pulls straight off
-Adjustable mounting position

http://www.midwayusa.com/product/779085/caldwell-brass-catcher-ar-15-picatinny-rail-mount-nylon-mesh-black

If i was stationary and constantly shooting the same direction I would just use a tarp like the last poster. They work for every caliber/firearm out there. However, I need a brass catcher for shooting gophers from a pickup or 4-wheeler.