Barrel/Paint Fit Question

I have a J&J Ceramic barrel.  My last case of paint was Draxxus Midnight.  With that paint, I could drop a paintball right through the barrel with no stoppage.  Yesterday, I bought Draxxus Blaze.  The guy at the Paintball store showed me that proper paintball fit should be like a "spitball" in a straw.  (The paintball should stop in the barrel and you should be able to lightly blow the paintball out.)  Well, the Blaze seems to fit perfectly.  

Now to my question...I still have about three guppies of the Midnights left and I want to use them up at the field, tomorrow.  So, when I chrono my gun, I would imagine that the Midnights would give me a slower reading than the tighter fitting Blaze, due to the fact that the loose fit would give some gas "blow-by" thus not utilizing all the gaseous energy.  Does this sound right?  How much velocity difference do you think there'd be with the two different fitting paints?

Sorry if this is a dumb question, but on the one hand, I'd hate to chrono one paint and then when I'm on the field loading my hopper with the other paint, find out that the balls just dribble out of the end of the barrel.  On the other hand, if I chrono to the loose fitting paint and on the field put the blaze in and find out I've shot a ball right through an opponent.

Anyways, thanks in advance for you opinions and answers to my questions.....