Anderson AR-15 lowers no longer mil-spec?

Patrick R
by Patrick R

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.

Photo credit: AR15.com user MaverickAA

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.

Photo credit: AR15.com user kwrangln

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”?

Patrick R
Patrick R

More by Patrick R

Comments
Join the conversation
2 of 75 comments
  • Barneysamson Barneysamson on Sep 04, 2015

    Mountain out of a mole hill imo. Use a thick (or multiple) washers. Or cut the fastener to make shorter. No nut or die is absolutely needed to thread onto a bolt before cutting it off shorter, although it's a good practice. That is, unless you're using a chainsaw to cut the bolt off. You WILL want to dress the cut end w/a dremel or fine file though. Unless the hole needs threads all the way through the hole (like to adjust the trigger by the method everyone's aware of), just leave it as-is. Cutting the threads w/a tap risks damaging the existing anodization, as well as will create a non anodized area in the lower.
    FWIW, some if not all DTI lowers also do not have threading all the way through- but a 1" length-under-head fastener works just fine, so I'm wondering if a 1" fastener was even tried or if the assumption was made it would not fit w/o actually trying it...

  • Barneysamson Barneysamson on Sep 07, 2015

    Those who insist that every detail be mil-spec will be put off, no doubt. Mountain out of a mole hill imo. Use a thick (or multiple) AN flat washers. Or cut the fastener to make shorter. No nut or die is absolutely needed to thread onto a bolt before cutting it off shorter, although it's an oft-used practice. You WILL want to dress the cut end w/a dremel or fine file- regardless if a nut or die is used. Unless the hole needs threads all the way through the hole (like to adjust the trigger by the method everyone's aware of), just leave it as-is. Cutting the threads w/a tap risks damaging the existing anodization, as well as will create a non anodized area in the lower.
    FWIW, some if not all DTI lowers also do not have threading all the way through- but a 1" length-under-head fastener works just fine, so I'm wondering if a 1" fastener was even tried or if the assumption was made it would not fit w/o actually trying it...

Next