Before you spend all your money on a spool gun, try a few inexpensive things 1st. Are you running a teflon liner? If not, then that's your 1st step. Are you using U shaped drive rolls or V shaped drive rolls? You should be using the former. Use 5356 alloy wire, I've found it to be the best with regard to wire feed problems. When setting the amount of load on the drive wheels, use just enough pressure so that the rolls will slip rather than making birdnests.
Wires smaller than 1mm will have feed problems we generally use either 1mm or 1.2mm. (sorry, we use Metric here in Australia and I'm not sure what the Imperial measurements are.)
Use tips especially made for Aluminium, they are slightly larger in diameter than those for steel. or drill your steel ones out slightly larger.
One problem we found when using Teflon liners was that the wire has a tendency to arc at the back of the tip where it screws into the gun, causing burnbacks to the tips. We resolved this by modifying a Binzel screw on Brass liner section which just went through the neck of the torch and no further.
Try these things first it may save you a lot of money. We weld Aluminium all day using 3.5 metre (12 foot) Tweco No 4 torchs and we have solved most of our feed problems.
Hope this helps. Regards Andrew.
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