SpudFiles

Ok, ball valves constrict flow. We all know that but say that I had a 1 1/2 chamber with a 2 in ball vave with a 1 in barrel would the larger valve help all the chamber open open up alot quicker?

alot quicker then what.....?is it worth buying a large ball valve arn't they expensive?

Yes, you could get better flow with a larger ball valve, but have you ever tried to open a 2" ball valve (they are very stiff) also they are expensive in fact you could get a sprinkler for less than a 2" PVC ball valve. Even with a 2" valve you would still get better flow with a non-modified sprinkler valve, and since you're talking about a 1" barrel, a 1" sprinkler valve would be perfect

ball valves constrict flow.

they dont constrict flow, they just open slow.

And thus Benny shows that he doesn't understand WHY things that open slow are bad.

Yes, using a oversized ball valve will improve preformance, assuming that a 2" valve doesn't take 4 times (if my logic holds) as long to open as a 1" valve.
Which I'm pretty sure they don't.

However, your 2" ballvalve still underpreforms a sprinkler, even with a 60" barrel (assuming 200 ms opening time):

Ball valve: 380 fps
unmodified sprinkler: 414 fps

Both with a 94 ci chamber, 60"x1" barrel, 100 psi, 25g projectile.

Your best bet would be to make it so that springs would open the valve. They have to be tight tho so it will open fast. But if you are going to do it by hand you best bet is use dual modded valves.