yup that's how you do it. add by small portions and the usual "trial and failure" method. For me, I only needed 2 shims, but everyone's is different, just like gearboxes.

Alrighty, Brodie_BHD as been kind enough to send me a few extra's he had. Ill report once they arrive and have a chance to try em out.

so basically this wobble problem is remedied by pressing the barrel down by way of the fake gas tube?

the gas tube only stabalizes the barrel, the shims as pictured are used to cause preasure which makes a tighter fit, which reduces or eliminated wobble