Measuring of Paintball "Fit"

Hello,

This will be my first post on the board and I would like to say I'm new the sport, just got my old cheap model 98 a week ago, and would like a little information regarding the desired dimensions of the paint compared to barrel it is to be fired through...

I'm currently using a digital slide caliper to measure the paint and the largest reading I'm getting is .670" and the lowest is .650". The paint is of unknown origin and was given to me by a friend but I'm pretty sure it is cheap Wal-Mart stuff (I just don't know the brand). But isn't this a horrible tolerance? Some of the tolerance may be in the measuring devices "squeezing" the paintball but if so what other devices do the pros use to measure their paintballs?

After multiple measurements of both my Boomstick and stock barrel they come out to .687", so is this paintball a horrible fit in this barrel? I am having some accuracy and consistency problems but of course I'm just starting out and also have some questions regarding the gun adjustment...

Even it may be accounted to my poor aiming my gun currently can't stay within an acceptable "pattern". One shot may be decent to my sights, but the next may miss the target completely. A friend of mine with an out of the box 98C Pro can put me to shame in terms of speed of firing, accuracy, and consistency, and his gun has a much higher velocity than mine. Would an expansion chamber may help me this significantly?

Any general rules for gun adjustment, mods, and techniques to improve my accuracy would be very appreciated, thank you.

Paintballs are just not really accurate at all, or atleast the kind you bought.  To test the size of the paint, instead of measuring it, just drop it into your barrel, and if it falls right through, it's too small, and if it's stuck, and you CAN'T push it out, it's too big.  If it slides through slowly, or usually touches the sides, or you can push it through, with no problem, and it doesn't fall through, it's fine.  An expansion chamber will help your velocity be more consistent, and not spike as much.  

Paintballs aren't made to bullet tight tolerances. The thing to remember is that there is more than size to affect performance of the paint...one of the biggest issues is quality of the paint, and the current condition of it.
Big chain stores like Walmart aren't the best place to buy paint, beause they won't be likely to take care of it like a paintball shop would...keeping it from freezing, or letting it melt, or simply storing it in a warehouse for way too long until the paint get all dimpled.

A good rule of thumb is that when attempting to insert a paintball into the breech end of the barrel, it should not be so small that it rolls out the barrel, but it shouldn't be so tight that you have to force it into the barrel. Otherwise, that should be all the more you should need to know about paint/barrel match.

Really? Can you get a spring to easy replace it or do you have to talk to tippmann? 

put a paintball in the barrel and look down the barrel (when its off the marker obviously) and the paintball should touch the barrel at 3 points. any less and its too small more and its to big

Springs are available from most paintball stores...one example here.

Small bore paint for the flatline. The flatline is one of two exceptions for the "good paint to bore match." .680 would be about right.

i BLOW my paintballs through the barrels to find the best match

Its a good rule of thumb that if you put a ball in the barrel, and there are three points where the ball is touching the barrel. Thats a good bore match.

You can send the faltline in to tippmann to get the inside reblasted if you believe it needs to be. They should do this for free. Call them up.