ab (Apache Bench) issues on OS X

I am having frustrating issues with trying to perform a highly concurrent test using ab (apache bench) on OS X. A snippet of the output looks like:

Completed 1998 requests
Completed 2664 requests
Completed 3330 requests
apr_pollset_poll: The timeout specified has expired (70007)

The command I am running is something like: (I would like the concurrency to be even higher! My goal is to get at least 20,000 rpm to hit the server)

ab -k -r -c 400 -n 60000 [URL HERE]

Has anyone run into this -- love a push in the right direction? And I would love to do this on my mac.

My Environment:

• OS X : 10.6.8
• httpd : Apache/2.2.20 (Unix)
  • Architecture: 64-bit
  • Server MPM: Prefork
  • threaded: no
  • forked: yes (variable process count)
• ab : Version 2.3 (built from latest apache http beta)
• ulimit -a yields:
  • core file size (blocks, -c) 0
  • data seg size (kbytes, -d) unlimited
  • file size (blocks, -f) unlimited
  • max locked memory (kbytes, -l) unlimited
  • max memory size (kbytes, -m) unlimited
  • open files (-n) 1024
  • pipe size (512 bytes, -p) 1
  • stack size (kbytes, -s) 8192
  • cpu time (seconds, -t) unlimited
  • max user processes (-u) 266
  • virtual memory (kbytes, -v) unlimited

I have found an awesome utility that solved my problem elegantly:

Bees with Machine Guns!!

Repository: https://github.com/newsapps/beeswithmachineguns

Blog entry about it: http://blog.apps.chicagotribune.com/2010/07/08/bees-with-machine-guns/