Well it figures.  I just received my approved form 1 in the mail last Saturday, so I headed to the range this Saturday to shoot my new SBR for only the second time.  I have actually had this lower for several years and probably have a couple thousand rounds through it.  I only got through about 90 rounds this Saturday before I had my first ever malfunction.  After ejecting an empty magazine and inserting a loaded one, I attempted to release the bolt with the bolt release button but noticed it had no tension.  I then tried to release it using the charging handle, but this did not work either.  Basically the bolt was jammed in the open position.  After scratching my head for a few minutes, I decided to pack it in as I had no screwdrivers to remove the offset pin to separate the upper form the lower.  I went to my favorite gunsmith since he was closer than home, and we managed to get the two halves apart.  When we did, a small piece of metal fell out of the lower.  A brief inspection reveled that the bolt catch had actually sheered off and became wedged under the bolt, preventing it from closing.  My smith said that this wasn’t all that uncommon, but in eight years of shooting AR’s I have never before seen this happen.  In the end the gun will now function again, and no permanent damage was done, but is this a common failure item?  Should I have a couple extras on hand?  Was there anything I could have done to prevent this from happening, like using the charging handle vs. the release button to close the bolt?  Any input or experience anyone has with this would be greatly appreciated.  

-Matthew

The bolt catch/release on the 9mm lower is the same one as the 5.56mm variant lowers, I've slammed on my bolt release/catches for years w/o a problem, and so have millions in the military.  Ideally I "try" not to run dry and depend on the catch to let me know I'm on "E" , but  when I do go dry I am not gentle on the release, I want to make sure I hit it prompptly and surely.  I've never experienced this phenomenon, or heard of it.  I've seen 1 maybe 2  bolt releases "go" on older lowers, but due to high round counts and MANY years of service/abuse, but is it a "particularly" common part that needs replacing? No, not in my experience, maybe just a fluke.

Actually, the bolt catch for the 9mm lowers [b][i]Are[/b][/i] different.  The have a long skinny arm that is required to reach over the width of the magazine block.  I really had never paid any attention to that fact until this one broke, but while at my gunsmith’s, we were just going to replace it until we discoverd the difference in the two.  He only had catches for the standard .223 on hand.  I had to order the 9mm version this morning from Brownell’s.  Unbelievable these things cost $20.00 each.  I ordered two using the governments …why have one when you can have two at twice the price…policy.  If it broke once, it may break again.

You, got me...
1. I'm disappointed I've never noticed/realized the difference.
2. I'm sorry If I wasted your time/gave mis-information.

Sorry about that, but shoot up that 9, and let us know, huh?  Was the differing part the aspect of the catch/release that broke?

You only need the 9mm specific catch if using Colt factory pin-in mag blocks.  The Colt 1 piece slide in mag block (as well as many aftermarket slide in blocks) was designed to use the 223 bolt catch.  The 9mm catch will break sooner or later; it makes sense to have spares of just switch to the 223 one and use slide in blocks.

SULACO2, don’t feel bad.  As I said, I’ve been shooting AR’s for eight years and only noticed the difference after this one broke.  That’s what these forums are for…Sharing information.  The part that sheered off was not the unique arm of the catch.  I broke internally, just behind where the pivot pin secures the catch to the receiver.  I could see it happening on my .223 catch also.  

Hail Mary, excellent gouge on the mag-blocks.  I am in fact using Colt factory pin-in mag blocks, as this is a factory assembled and marked 9mm receiver.  I don’t want to remove the pinned in blocks just to switch to a different style.  I guess I will just replace the catch and hope that the failed one had some sort of manufacturing defect that caused its demise.