It appears that Anderson has made the decision to change the thread depth on their AR-15 lower receivers so that they will not accept the standard 1″ grip screw found in every mil-spec AR-15 lower in America. In the photo below you can see that the grip screw hole is not threaded the whole way through.
My friend Scott from The Gunshow Podcast (a great podcast if you haven’t checked it out) let me know that Anderson claims that the 1″ grip screw was creating malfunctions by interfering with the fire control group. I have also have seen rumors on ar15. com that there was a manufacturing error that left the threads unfinished.
Some AR-15 builders have decided to take the matter into their own hands with a 1/4-28 tap, threading the hole the whole way through. This is a sure fire way to fix the issue if you feel up to the task.
Anderson sells a 3/4″ long grip screw that will not run out of threads before being fully seated. They have it priced at 99 cents, but was a bit shocked when I saw the shipping price of $11.22 for ground shipping on just the grip screw. Did I put the zip code if for the moon?
Alternatively, builders can just run down to their local hardware store and buy a 1/4-28 screw that is 3/4″ long to get around the threading issue. Do you think that the fact that you can no longer install common grip screws changes Anderson Manufacturing lowers status as “mil-spec”?
This post originally was run on The Firearm Blog - http://www.thefirearmblog.com/blog/2015/08/28/anderson-ar-15-lowers-no-longer-mil-spec/