The military tech manuals call for 35-40 inch pounds of torque on the gas key screws. I had read here and elsewhere that the desired torque range would be 50-59 inch pounds, thus the selected 55 inch pounds of torque for these screws. Is the higher torque specification because of the higher gas pressures involved in carbines or is it just because the military manuals are old? Or is it because of recent information? Thanks.
The gas key screws are one part I’ve never put a torque wrench on. I usually just put it to them until the allen wrench starts flexing. I probably put too much to them but I’ve not had a problem doing it that way for years.
55 in/lbs. really isn’t that much torque (a little over 4.5 ft/lbs). I bet most would exceed that just using a small allen and tightening like seb5 does. The one issue I’ve always wondered about (and have seen once in person) is how overtorqueing affects the screw. The issue I saw (and I am just guessing here as to the cause) is a gas key that was very loose but had the proper staking. What happened was the front screw broke at the head and allowed the key to wiggle around causing the normal issues a loose key causes. Either it was just a POS pot metal screw that couldn’t take the proper torque or it was overtorqued then staked putting a lot of pressure on the screw head. I have learned from my line of work that too much torque is just as bad as not enough and it really depends on the strength of the fastener used whether it be a nut, screw or whatever. This is especially true in this case as the military I’m sure has probably specified exactly what grade the gas key screw is on their rifles but with the abundance of other manufacturers in the civilian world of AR’s who knows if they use a quality screw or just whatever they can get to save a few cents. Sorry, I am rambling on and really don’t have an answer to your question so I will let the more experienced chime in.
Thanks for the comments, guys. I’ve seen broken scope ring screws but no broken gas key screws. It makes sense that inferior fasteners would break more easily. I’m just trying to nail down whether the 55 inch pounds is good or not as I thought it was the standard until I ran across a TM.
ASA shipped a friend of mine a BCG with a broken gas key:rolleyes: