If you're at 2.5mm you have a few options. See how well that works. OR, if you can devise a way to restrain the tubing *that will try and pop out* you can drill to 4mm and insert a 4mm OD 2mm ID teflon tubing that will make the barrel less jam prone. But you need a clever way of preventing the very substantial desire for the tubing to jump up. Some people on Qu-Bd used this as a solution for the Qu-Bd extruder that jams easier on account of its steel barrel.

I have a couple questions: 1) The barrel that broke had about a 3.5mm ID.  This seemed a little big for the 1.75mm filament I am using from Solidoodle.  I drilled the new one at about 2.5 mm.  Was this a good idea or bad?  Should it be even smaller (like 2mm)?  2) The new barrel is made from regular steel, not brass.  Is that good or bad?

So far it is working, but I only used it for about an hour.  We'll see if I get another clog.

Maybe it's time for a more robust hot end. $59 for a new hot end if you get a plugged nozzle seems a bit, HMMM, expensive! Now I just took mine apart and put it back together fine but like you said some of the people out there may not be able to pull it off. I just happen to be a retired mechanical engineer raised by a watchmaker father so I have the time, tools and patience to do it.

You never know what we're working on Seriously, we understand the shortcoming of the current design. Look out for cool things in the future.

If you want, you can machine it yourself. The drawings are released on the web.

Solidoodle informed me that if you unscrew the brass barrel from the peek insulator you ruin the threads and it will leak when you reassemble it. I think they are trying to sell more hot ends.

The PEEK retainer gets up to glass transition temp during normal operations. The threads are ruined in most cases. When we used to provide people the barrel, we saw all manner of mishaps including leaking barrels, snapped barrels during assembly etc.. while the barrel might work for some, there is an equal chance it might not fit into a used PEAK retainer leaving Solidoodle in the wrong for providing a part that doesn't work. In general we are trying to get people away from taking apart, or assembling their hot-ends. The Solidoodle hot-end is fairly fragile, and we have seen many instances of Solidoodle users breaking theirs in attempts to repair it. We know from (unfortunate) experience that the hot-ends can be tricky to build, so we try to make sure everyone gets a solution that works for them the first time.

For similar reasons, we generally do not recommend that users remove their nozzles either. Many users can manage removing the nozzle, but the parts that make up the hot-end are soft, and we have seen plenty of examples of users breaking parts when they were meaning to fix them. Generally speaking, it is much safer to remove the nozzle off a fresh hot-end than a thoroughly used one. If you're experienced with machines, go for it. I'm sure many forum readers have no problem popping off the nozzle, but for many newer Solidoodle users it can be a recipe for breaking things.