Installation Tips

Installation tips:

Does size really matter? The Option Zero is designed to fit snugly onto your rifle.  This important to the overall feel and shoot-ability of an OPTION ZERO equipped AR.

It is important that you choose the right size stock, based on the specifications of your rifles buffer tube.  Currently, we are only offering our stock in “true Mil-Spec” spec.  We are developing a fit for commercial and oversized Mil-Spec stocks, which should be available mid 2nd quarter 2017.


Buffer tubes: 

Generally speaking, buffer tubes (also referred to as “Receiver Extensions”) come in either Mil-Spec or Commercial diameter. There are several differences in the way the two are constructed, but for fitment purposes, the main difference is that commercial tubes typically have a diameter of 1.168”, while the Mil-spec tubes are slightly smaller, with a typical diameter of 1.148”.  Our Mil-Spec version of the OPTION ZERO is designed for “true” Mil-Spec buffer tubes and castle-nut only.  We are currently working on a version of the OPTION ZERO that is compatible with commercial diameter buffer tubes.  We expect the commercial variant to be available sometime in May, 2017.

  • Mil-Spec or “mil-spec”? Regrettably, in some cases, tagging a part with the phrase Mil-Spec or Mil-Standard these days seems to merely provide a vague suggestion of the parts dimensions.  This is more often found with some of the bargain basement AR parts, so as a general rule of thumb it’s best to but quality parts.  Stick to well known, high quality suppliers and you shouldn’t experience a problem.  One tell-tale sign is a buffer tube that has a noticeable step-up in diameter behind the threads. If you have a buffer tube with a significant increase in diameter, it’s always a good idea to use a micrometer to verify the diameter along its full length.   This also applies to castle-nuts, which can vary tremendously in size.  

INSTALLATION TIPS: (Note: The easiest way to work on any AR is by utilizing one of the many polymer mag blocks that you can secure into a bench vise.  You will need a 5/32 Allen Wrench, one is provided. Non-permanent thread locker such as Blue Loc-Tite, Gun-Tite or Vibra-Tite is recommended)

Grip: The TangoDown BG16 grip, which is provided, is an integral part of the OPTION ZERO system. 

  • The BG-16 is slightly tapered where it meets the receiver.  This is a design feature intended to make the grip mount in a solid fashion with little or no ability to move.  It helps if you start on one edge and then slide the grip onto the receiver.  If you’re experiencing trouble keeping the detent spring in the grip, simply apply a tiny dab of grease to the spring and slide that end into the recess in the grip (his will keep it from falling out).  On initial installation, it’s a good idea to apply some blue Loc-tite or Vibra-tite to the threads of the ¼-28 grip screw.

Note: take particular caution to insure that your safety/selector detent does not fall out when the grip is removed.

Stock: before getting too deep into the installation process, it’s always a good idea to dry-fit the stock onto your buffer tube.  It should slide on with only a minimal amount of effort.  If you encounter resistance, please check the dimensions of your buffer tube in order to verify that you have the correct size (true Mil-Spec).  If your tube is out of spec, or non Mil-Spec, it is likely that you will need to acquire one of our stocks in “commercial” size.
  • Make sure that your buffer tube is clean. This isn’t a functional requirement, it’s just that you might not see your buffer tube for a while and you might as well take this moment to clean it.
  • Make sure that you grip is properly installed
  • Slide the Option Zero butt-stock onto your buffer tube (making sure to remove the spare parts kit from the stock first) until the grip tab slides into the recess in the bottom of the grip. Make sure the tab is aligned with the grip recess before sliding the stock fully into position.
  • The Option Zero secures to your rifle by a single ¼-20 bolt that screws into the aluminum bushing in the BG16 grip. It is critical that the hole in the bushing align with the hole in the tab before attempting to secure the bolt.  If the two holes are not lined up properly, there is always a danger of cross-threading the bolt.  It is always a good idea to either give the butt a good smack with a rawhide or rubber mallet (if you have the assembly in a vise) or simply “mortar” the rifle by smacking the butt against the ground.  This should fully seat the stock, compress the foam and properly align the two holes.


  • Your OPTION ZERO is supplied with three spacers.  If you desire to shorten the length of pull on your stock, you will need to remove spacers. It is possible to run your stock with one, two or three spacers.  In your stock, you will find a spare parts kit that has two sets of 10-32 butt-plate screws.  The shorter, 1-1/8” screws are intended for use with one spacer.  The midsized 1-1/2” screws are for use with two spacers and the 1-3/4” screws that came installed are for use with the 3 spacers.   Do not attempt to over-tighten an incorrect screw combination as it could lead to damage.


  • Stock too tight?
    • If the stock won’t slide onto the buffer tube with minimum of effort, then chances are that the buffer tube is not “true Mil-Spec”. Please refer above to section on buffer tubes.
    • If your stock becomes stuck onto your tube, the best way to loosen it is to remove the butt-pad and spacers, which will allow direct access to the rear of the buffer tube. Simply take a wood dowel and lightly tap the receiver forward.  This will remove the stock without any damage.
  • Holes in grip and tab won’t align?
    • Odds are that the cause here is a slightly out of spec castle nut. If the holes are only slightly off it’s possible to get them to line up by simply applying some light pressure to the grip (pulling it back towards the stock) and getting the holes to line up.  An easy way of doing this is with a padded c-clamp or a set of wood clamps.   If the holes are grossly off, or light pressure doesn’t align them, then the issue is the most likely the out of spec castle nut, which will require replacement.  

As always, please feel free to contact us with any questions.  If you have any specific technical questions or need any advice or help on installation, please email .