After reading the posts above I’m not sure what type tubing you are using or what material you are fastening to it but I’ll show an example of an older project I put together.
Here I’m using 1/4” structural rivets to fasten an 1/8” thick bracket to 1x1, 1/8”wall, 6061, aluminum square tube.
This tube and brackets are going to support an interior cargo basket between the Sport Bars on my Jeep.
This was the first project where I used this rivet gun. My old (30+ year) hand operated hydraulic gun gave up the ghost and wasn’t cost effective to repair.
I think this is the unit I purchased:
Tool Aid 19250 1/4" Super Duty Riveter
https://www.amazon.com/dp/B0002SRG1Q/ref=cm_sw_r_cp_tai_KU.QCbRQ97AQ3
I think I bought mine at O’Rileys because I was in the middle of the project when old faithful died.
I’ve used it approx 100 times since I bought it and it has performed well.
The above unit will set rivets from 1/8” to 1/4” with minimal effort.
If money were no object, (yeah right), I would buy the air over hydraulic, Cherry brand, rivet gun that we had at work for only $1,000 or so.
The rivets I used were an aluminum, Cherry brand, 1/4” structural rivet. Sorry, I can’t tell you the exact part number because I just used some rivets of the correct length that I had in my tool box when I retired.
The exact number isn’t important to you as it’s dependent upon the specs of your application.