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.

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

Solution

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

Bees with Machine Guns!!