ArmaLite’s M15 Vise Jaws are similar to the U.S. military’s vise jaws. They will hold any M-15 Upper Receiver (EXCEPT OUR SPR MOD 1 SERIES) in an upright, horizontal position. However, unlike the military jaws, the ArmaLite Jaws are made from a nonmetallic material so, properly employed, they shouldn’t damage the finish on your firearm. They are primarily used when changing barrels. These Jaws clamp on the sides of the upper receiver.
--When using these Jaws, it is important not to clamp the vise too tightly. Doing so could deform the upper receiver. You can insert your bolt carrier with key (without the bolt assembly) in the upper receiver to provide additional support. But, still use caution.
-- Be sure to close the ejection port cover before placing the upper receiver in these Jaws.
Technical Note 90: ArmaLite Vise Jaws and Blocks