who makes 20" chrome lined AR barrels?

An ArmaLite M15A2.

They make a 20" model.

All of their M15A2 rifles are 5.56 AND .223 capable.

They are all chrome-lined.

All their base model M15A2s have a standard thread and come with an A2 flash hider.

All their base models have a 1:9 twist.

They all have heavy profile barrels.

And I absolutely LOVE mine. What a fantastic gun! M15A2 with 20" barrel, fixed A2 carry handle sights, OD green furniture. Shoots like a dream.

Have you looked at the barrels offerend by www.midwayusa.com or brownells.com? There is certainly no shortage of nice barrels online.

I have been using the Daniel Defense milspec barrels - like what you are looking for - the past two years and I am very impressed with them. I needed a 10" barrel for an SBR I was building, they were only ones that made it - and for the price I was expecting crap, but, I struck gold.

Be sure to check out the equipment exchange at www.ar15.com for barrels and other goodies. The barrel you are looking for is a very popular 'take off' that sits in a closet when folks upgrade to a match or varmint barrel. You could score one for little money there. They will even let you post a wanted ad for free. It's a great place to get common parts and ocassionally hard to find mispec parts.

YHM. My son got one without the threaded barrel. Good luck finding ANY AR-15 parts.