My Lincoln's all have the same outer body size, we only change the collet itself for tungsten sizes.Does any company make, for instance, 1/16" or 3/32" ID collets with the same OD as a 1/8" ID collet?
Are you using 2% thoriated (red) tungsten?
I have welded some pretty crappy material 1) If you take too long to make your puddle it will boil (porous fizziliy mess), use more amps.
2) Get GOOD quality filler into the puddle asap, this seems to displace the impurities and calm everything down. I find that using SS filler on the crappiest material works brilliantly.