Data is showing 2.26" for COAL. I checked my chamber and I'm coming up with 2.23" to the lands. How short is too short? Would 2.22" and .5 gr off max charge be too much?

How did you check to the lands?

I would drop a grain or so and work back up with a new COAL.

Quoted:
Data is showing 2.26" for COAL. I checked my chamber and I'm coming up with 2.23" to the lands. How short is too short? Would 2.22" ...

It's your rifle and your chambering.  Measure it carefully and load accordingly.  There is no such thing as too short.  It has to fit your chamber.  

If your chamber is too short (below SAAMI minimum) send the upper back to the maker and have them rework the chamber or replace the discrepant barrel.  


...0.5 gr off max charge be too much?

Work up the load.  If 2.220" is your OAL, work up a load for that.  It isn't really possible to say what will work best for you given the scarcity of information you've given us.  For me, load development isn't just about charge weight and I NEVER use "max charge" for anything (except as a warning to stay away from it).  You should, too.    

Measurement was done by dropping a rod down to the bolt face and marking it. Then inserting a projectile and pushing it into the lands then marking the inserted rod again. That gives coal for that round..

I've gotten 2 Grendel barrels from Anderson and classic. The Anderson was too short to use and I had to send it back. I'm thinking this one is serviceable

That method has two drawbacks that came to mind.  

1.  It measures to the tip if the bullet.  Tips on HPBT bullets vary quite a bit (+/- 0.010").  That means that within the same box of bullets you could be off by 0.020" just because you randomly picked a long one (or a short one).

2.  Bullet ogives and bullet OAL changes quite a bit from die-to-die, lot-to-lot, even though they are the same maker and same part number.  

3.  I'm not sure how you marked and measured the two dimensions but when I tried that I could not convince myself my numbers were accurate to within +/- 0.010".

Add to the above the fact that it is not the tip that's important, it is the engagement of the ogive into the lands that is critical.  

It all adds up this - buy the Hornady gages. You'll get accurate, repeatable numbers to work with.

There are ways to get those numbers without buying the gages but it requires more work on your part and I don't feel like typing out the instructions right now.

I had same issue with my Shilen barrel...
https://www.ar15.com/forums/armory/Grendel_OAL_Question____Bullet_hits_the_lands_way_short_of_book_values/42-428099/?

Had to send it to them (on my dime!) to remedy it. These barrels should be able to feed store bought ammo... Mine couldn't do that. Took way too long to convince Shilen there was a mistake. I would have returned it to Brownells had I not had it threaded.

But it worked out in the end. Shoots great.

.03" Not sure that is a huge deal... My Anderson barrel was way off. If I let the bolt fly on a mag it would jam in so hard that it would pull the bullet out of the case and powder would fly everywhere.

What bullet?

If you are using the 120 AMAX, that is normal.  If you are using just about any other 6.5 bullet, that is a problem.