In the article I posted last week about the Sig Sauer stabilizing brace I included a picture of a reviewer shooting an AR pistol equipped with the brace.

The pistol in the picture also featured a vertical fore-grip and I received a number of questions concerning the legality of adding a vertical fore-grip to an AR pistol.

The ATF has long held that adding a vertical fore-grip to a pistol makes it an AOW subject to the requirements of the National Firearms Act (NFA).

However, like so many ATF regulations, this one needs further clarification. If the overall length (OAL) of the pistol is greater than 26 inches then adding a vertical fore-grip doesn’t result in the pistol becoming an AOW. The following letter from 2011 breaks down the ATF’s position:

To summarize … unless your AR pistol has an OAL greater than 26 inches then you should not add a vertical fore-grip unless you first submit a Form 1 and get it approved.