Dual sheild 71m, Push or pull?

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I'm splicing 12x8x5\16" tubing for hospital stairs. Being over 1/4", they need to be ut'd. Well I've been ut'd many times and hadn't had any problems, till now.  Not all the splices but some with 1 to 3 inch hits on the ut machine. Anyhow boss thinks cuz I'm pulling 1/16th 71m dual sheild with co2. Inspector could careless. I mostly welded with fluxcore, 232, 305 and I pulled. It turns out it was the shape of the tubing and also the backup bar is a solid 3/4" flatbar cut to fit around the inside, which means there are voids, especially near the seam where all of the hits occured. Slag inclusions at the edge of the flat bar. Now to the point, push or pull, whats the difference anyway?
Reply:I dunno, I hear it both ways all the time. I was taught this way..."If it has slag, you must drag". That is the way I will continue to do it...regardless.
Reply:Originally Posted by heavymetal_2006 bar is a solid 3/4" flatbar cut to fit around the inside, which means there are voids, especially near the seam where all of the hits occured. Slag inclusions at the edge of the flat bar. Now to the point, push or pull, whats the difference anyway?
Reply:You can drag 71M but it is designed to be pushed also try using .045 as it doesn't get cold lap as easy as 1/16. also whats your voltage I tend to run at 26 volts and 175 inches for 1/16 and 3oo inches for .045. Also is the inspector green because regardless of joint prep loose or tight a good inspecter will notice the discontinuity is below the weld zone and won't fail the weld.
Reply:Yeah. Thanks for the reponse. Tubing is not square. Hence when using flat bar(on it's edge) for back up it wont be completly flat against the tube. I like to use 1/4 by 1" backup, cuz it'll shape to the tube. But, whatever, boss knows better. But to resolve it, I used Bessie clamps to clamp the tube down at about two inches away from the weld.