5.7x28 p90 ar upper.

[AK4me]

Check it out, I havent seen one of these before.

http://gunbroker.com/Auction/ViewItem.asp?Item=119269912

[Quiet]

Previous thread on the AR57.

http://www.calguns.net/calgunforum/showthread.php?t=136977&highlight=AR57

Magazine lock for it is on a custom made basis and not widely available.
Therefore, if you get one, you'll need to place it on a featureless build.

You can get factory 10 round P90 magazines now.

[TheBest]

How is the flash suppressor legal in CA?

[jrsportssupply]

They fit nicely on a RAW!