This morning I went out and played some woods ball with my a-5 (toatlly stock except for an r5 hopper).  The gun worked great and only chopped 1 ball, but that was right at the tip of the barell and ewas cleaned in seconds.  The gun fired about 350 rounds of Draxxas "midnight" and worked perfectly.  I did the thing where you put some gun oil in the asa andthen re gas the gun and then dry fire 20 shots or so. 

When I got home I decided to take the gun's internals out, oil up the o-rings and clean everything up.  The first thing I noticed when I stipeed the gun was that it was very hard to get the "power tube" to slide out.  I ended up having to poke it out through the tombstone hole with an allen wrench untill I could grab the rod that connects the whol thing and pull it out by hand.  I cleaned out the gun and put everything back togeather, however when I tried to put the tombstone back in, there was a spring and a loose o-ring in the way.  I looked at the manyal a tried to remove the whole valve assembly to make sure everything was in there, however I couldn't get the valve to budge.  I eventually got the sping back down and popped the o-ring into the small hole over it so that there was room for the tombstoe to go back in.  The gun seems to work fine when I cock and fire it with no air. (I haven't gassed it up due to the fact that its 2 am and I live on a college campus)

So here are my questions:

1. Is it really bad for the o-ring and spring to stick out into the arear where the tombstone goes?

2. Is it normal for the internals to be kind of hard to pull out/push back in? 

3.How are you supposed to remove the valve assembly from the power tube?

4.What kind of barell should I get for woodsball play (other than a flatline)?

Thanks

1.  The valve o-ring should hold the valve washer and spring in there when the rear bolt is pulled back (not pressing on the valve).  There is a recessed groove for the valve o-ring.  You didn't mention the valve washer... is it missing?  Take a look at your manual ( http://www.tippmann.com/support/manual/a5manual.pdf - http://www.tippmann.com/support/manual/a5manual.pdf  ) and see if you have these three parts inserted in the correct order.

2.  Unfortunately it is normal for the internals to be hard to pull out/push back in.  The best thing to do is to loosen your receiver bolts first, and they should slide out much more easily.  There are things you can do to make them easier to pull out (e.g. polishing the internals, etc), but Tippmann's claim that the A-5 is "field strippable", just isn't true on a stock A-5 (IMO).

3. After you remove the velocity screw, it is best to use the eraser-end of a pencil and push it out from the front of the powertube.  It is usually difficult to remove it the first time, but after it is removed once, it is much easier.

4.  Only the flatline, baby!!!

Good luck!