On Thu, 1 Aug 2013 00:09:09 +0000 (UTC),
wrote:

The middle 4 go in but one on each end doesn't.

That's what an 8 pin RJ45 crimper will do if you try to crimp a 4 pin
RJ11 connector. The end push pins ride up on the wide edges of the
plastic connector. Are you using an RJ11/14 die or something else?

On some crimpers, you can also produce that effect by not pushing the
plastic plug all the way into the crimper die.

I can't figure out if there's a way to change the head.

Some change the head, others change a die. Some have an insert.
You'll need to disclose what you have before that can be determined.

I think I've had this problem before and had a workaround but
can't recall

Why not essentially make an awl/screwdriver type push down tool that also
takes up less space?

It takes quite a bit of force to crimp those connectors. A 4 pin RJ11
may not take much force, but the 10 pin RJ50 requires leverage.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558