According to Fred at ClearAir Tools, there are 2 basic styles of rivet guns, the Ingersoll Rand and the Chicago Pneumatic and all the other brands are copies of one or the other. Both the IR and CP brands are good; my mechanic & I believe the CP's are a little better. I have an ATS that is a piece of junk; I have heard from some folks that ATS guns are OK; maybe they just haven't tried a good gun or maybe the newer ones are better than mine.
You can buy a CP clone from Avery & Bob says that all the parts interchange with the CP guns. There are other CP clones & I dont' know if they are as good; Isham has one for about $135. You can buy rebuilt guns, including CP's & IR's from ClearAir. You can buy used guns from The Yard; these are not rebuilt.
My IR started acting up. It's an old gun & has probably driven millions of rivets. The procedure for fixing them is to add lots of oil, keeping the trigger down so the oil will flow into it, then run it at 90 psi. You'll get lots of black goop out of it. That did not fix mine & I called Toolsez (an Ebay seller, pronounced "tools easy") & he sold me a well used CP for $90. When it came, I took my IR apart (nothing to lose, right?), cleaned it up, soaked it in paint thinner & when it went back together, it worked fine. BTW, I saw no evidence of wear in the gun, so just because a gun is old does not mean it is no good.
There are places in the wing of an RV-9 where an IR 3X is just a little too long to fit between the ribs to drive rivets parallel to the spar, but the CP which is a little shorter & fits OK; therefore I would recommend the CP over the IR.
Richard Scott
RV-9A
Wings