I have seen that the more expensive "professional" guns have a variable output of up to 100KvDC, but most "hobbyiest" guns are a fixed voltage. I, like alot of PCers, spray smal batches. No more than 1/3 Lb of powder at a time. But, the pieces can get very intricate and have multiple coating's(candys on chrome ETC) Having a variable voltage supply for the gun wound be an asset in alot of PC operations, without having to pay Hundreds for a "pro" gun. Wouldn't need to be 100Kv, but maybe 15-50Kv
Would give Caswell's gun a advantage over all the other small guns