Styrofoam ball cone substitute

OK, Closer analysis...

I plugged the mouthpiece and started dropping marbles down the 5 foot tube at approximately 45 degree angle.

Of the 81 marbles in the bag I bought

3 were oversized.

12 were close enough to the bore size that they took over 5 seconds to roll to the bottom of the plugged tube. These are select ammo for the purposes of this evaluation.

66 were small enough that they slid down the tube faster. If I had set a 3 second limit I would have probably twice as many as my 12 select marbles.

I shot two select marbles at a cardboard target 30 feet away.

They punched two layers of cardboard which is a bit better than typical performance for a stun dart in the same environment.

So, in review, I got 12 or more good marbles for blowgun ammo from the bag and the rest will be reasonable slingshot ammo.

After testing in my 5 foot CS .625 I tried to test with the 4 foot CS professional .625. The professional has a smaller bore and only would pass 8 of the marbles. Something worth noting.

Never trust a first impression.

Your dollar store marbles may be differently sized, etc.