It seems that `arc download` doesn't support chunked downloads, whereas `arc upload` does support chunked uploads.
```
> arc --trace --conduit-uri='https://phabricator.mydomain.com' download F92760
libphutil loaded from '/home/joshua/workspace/github.com/phacility/libphutil/src'.
arcanist loaded from '/home/joshua/workspace/github.com/phacility/arcanist/src'.
Config: Reading user configuration file "/home/joshua/.arcrc"...
Config: Did not find system configuration at "/etc/arcconfig".
Working Copy: Reading .arcconfig from "/home/joshua/workspace/github.com/phacility/phabricator/.arcconfig".
Working Copy: Path "/home/joshua/workspace/github.com/phacility/phabricator" is part of `git` working copy "/home/joshua/workspace/github.com/phacility/phabricator".
Working Copy: Project root is at "/home/joshua/workspace/github.com/phacility/phabricator".
Config: Did not find local configuration at "/home/joshua/workspace/github.com/phacility/phabricator/.git/arc/config".
Loading phutil library from '/home/joshua/workspace/github.com/phacility/phabricator/src'...
>>> [0] <conduit> conduit.connect() <bytes = 586>
>>> [1] <http> https://phabricator.mydomain.com/api/conduit.connect
<<< [1] <http> 1,224,952 us
<<< [0] <conduit> 1,225,282 us
Getting file information...
>>> [2] <conduit> file.info() <bytes = 179>
>>> [3] <http> https://phabricator.mydomain.com/api/file.info
<<< [3] <http> 437,911 us
<<< [2] <conduit> 438,102 us
Downloading file 'phabricator.box' (1,024,403,951 bytes)...
>>> [4] <conduit> file.download() <bytes = 212>
>>> [5] <http> https://phabricator.mydomain.com/api/file.download
<<< [5] <http> 55,982,948 us
<<< [4] <conduit> 55,983,142 us
[2015-05-29 00:49:10] EXCEPTION: (HTTPFutureHTTPResponseStatus) [HTTP/500] Internal Server Error
>>> UNRECOVERABLE FATAL ERROR <<<
Maximum execution time of 30 seconds exceeded
/usr/src/phabricator/src/aphront/response/AphrontResponse.php:159
┻━┻ ︵ ¯\_(ツ)_/¯ ︵ ┻━┻ at [<phutil>/src/future/http/BaseHTTPFuture.php:339]
arcanist(head=master, ref.master=8fe013b0ecb5), phabricator(head=master, ref.master=1aa8bc319b52), phutil(head=master, ref.master=693207bcd81d)
#0 BaseHTTPFuture::parseRawHTTPResponse(string) called at [<phutil>/src/future/http/HTTPSFuture.php:415]
#1 HTTPSFuture::isReady() called at [<phutil>/src/future/Future.php:39]
#2 Future::resolve(NULL) called at [<phutil>/src/future/FutureProxy.php:36]
#3 FutureProxy::resolve() called at [<phutil>/src/conduit/ConduitClient.php:58]
#4 ConduitClient::callMethodSynchronous(string, array) called at [<arcanist>/src/workflow/ArcanistDownloadWorkflow.php:99]
#5 ArcanistDownloadWorkflow::run() called at [<arcanist>/scripts/arcanist.php:382]
```