Wish the search was working, cause I'm sure that someone has already asked this, but....
The bolt hold open feature with our subguns is not working with the plastic followers of the 32 rd mags. The mags we have that contain metal followers are doing fine. There are no failure to feeds or spring or lip probs, just bolt hold back on the plastics. 5 of 6 won't stay back after last round. Colt says they have never heard of this problem with the plastic followers when I called them.
Any body have any thoughts, tests, solutions? Thanks alan
Colt is very aware of the problem. (Maybe your call was answered by a new employee on their first day?)
The original 9mm 32-rounders had metal followers that looked a lot like Uzi followers with the bolt hold-open tab welded on the back. Problem was, those mags had a tendency to "fountain" themselves empty when dropped while loaded. (I have no idea why the Colts were so vulnerable when the nearly identical Uzi mags are not.)
So Colt went back to the drawing board and redesigned the follower, and came up with the new plastic ones. Sure enough, they are no longer prone to easily "fountain" when jarred or dropped .... but like you said, the bolt hold-open rarely works correctly.
Colt no longer has any of the old metal-follower mags in stock, and they are out of production, so .... "Gee, we've never heardof that problem." I know of at least three LE agencies who have complained loudly to Colt about it, and all they do is replace the mags with identical mags having the same problem.
Now, the good news is that some 9mm mag blocks are more reliable with the plastic followers than others, including the pinned-in two-piece blocks. And if you have dedicated lowers, check out the 9mm bolt hold-open arm (which is wider than the 5.56 arm) -- if there is any wear whatsoever, it makes it easier for the bolt to slip off and slide into battery.
Beyond trying different mag blocks and checking the hold-open arm for wear, you're out of luck AFAIK.