Batch calling using call files

HI, I have setup Asterisk and did some preliminary testing of sending out 50 calls at once. I moved 50 call file records into the /outgoing directory and it seems that my server only sends 5 or 6 at a time before returning to the /outgoing directory and getting 5 or 6 more call records. This takes almost 4 minutes to complete the 50 calls (the /outgoing directory appears empty after about 4 minutes). I would like to know what setting or constraint is keeping my server from sending them all at once. I am using SIP and connecting to a VoIP provider that says I have hundreds of channels available to me.

I am also looking into using the AMI with Originate command for this process, but have not gotten that far yet.

thanks in advance for any pointers.