slightly digressing from the topic, but the blowpipe test is actually the worst choice when sizing paint. If you match the bore perfectly so that it has some resistance but blows through, due to slight variances in paint size even within a box, some will roll through and some will catch, resulting in inconsistent velocity. You're better going a size up or down, although underboring has proven to yield better efficiency as an added bonus.
obviously underbore if you're playing pump!