What is the spin test?

I check to see if it is an arrow problem last night. It isn't the arrows. I am shooting fine with field points.

I did check with one errant shot and think I got it down to one arrow. I removed it from the bunch and it occured much less frequently and with much less extremeness. I am still about 4" at 20 yards with the BH and then I will have the occiasional one that is 6". I am worried because this is under the most ideal conditions. My back yard on a foam target.

I have 4" viens that are oreintated right helical.

Any other suggestions?

Tom