Thanks. I went and double-checked. The margins stops are all the way out and pressing the margin release doesn't fix anything.
I've already checked the cog rail under the carriage without finding anything. And it doesn't feel like debris in the gears. It feels, and sounds, like I'm running into a solid block.
I shifted the type basket, in hopes that something was protruding, but still nothing. The carriage runs all the way to the right and rings the bell, but only moves about 3 spaces past the center to the left before hitting something solid.
And removing the platen just shows how round and smooth the feed rollers are. Nice, but not helpful.
I think I need a service manual.

Aaargh! It's backward again!
All the way to the left, not to the right.

Sometimes when a draw band has partially come off the main-spring, it can bind up when you try to do a carriage return and it only travels back 1/2 of the way.
.

ShadyDaze, before you put a bunch of torque on that screw to try to force it out, I strongly recommend trying a few alternative options first. Typewriter screws are much more fragile than modern versions, and are sizes and thread counts that aren't commonly used anymore, so replacements are hard to find. I've broken off or worn many screw heads on the first few machines I worked on - it is worth some patience on these old screws.

Some suggestions:

1) Try a little chemistry before force. I use Kroil. Put a few drops and let it soak in for about 20-30 minutes. Then, try only a moderate amount of torque. If it doesn't go. Put a few more drops and wait again. Sometimes, I let it go overnight. Usually, if you let Kroil do its work, it'll eventually come out with almost no hard torque.

2) Buy a set of hollow-ground screwdriver bits. A normal screwdriver is wedge-shaped. This means all the force you put into it gets transferred to the upper edge of the screw head slot, which usually smashes it and causes the screwdriver to slip (or worse, breaks the screw head). A hollow-ground bit is nearly parallel at the tip, so the force gets distributed across the entire tip / screw slot, giving you better grip, much less likelihood of slipping, and is much gentler on the screw head. One caveat: because of their shape, hollow grinds are a bit more fragile than standard bits. Luckily, they're fairly inexpensive, too. 

Chapman has a great picture describing it, below.



Chapman has a set specifically for typewriters, curated by typewriter tech Lucas Dul. I've got a Chapman gunsmith set that a machinist friend gave me when he heard I was restoring typewriters, and I've gotten extras from Chapman (The #88, #90, #93, #95, #97 are the ones I use). There are other manufacturers, but I've no experience with them.

They're also really handy to have around for any project on old, small screws..