Anybody know how to remove?

It looks like it just screwed in but I can not seem to get a good enough grip to unscrew. Its too smooth and round.

Am I missing something?

There's also a transverse pin that needs to come out.

Quoted: There's also a transverse pin that needs to come out.

Thanks. Can you give more details or point me to instructions with pictures? I dont see no stickin pin.

The piston/carrier is  cross drilled, a slightly overlength pin is inserted, then hammer peened into place, then ground smooth.

If you look really closely on the BC near where the gas piston is screwed into it, you might be able to faintly see where the cross pin is.

It is sometimes difficult to spot. Brush a little Dychem on it. You'll likely need to drill it out. The piston should unscrew at that point. Red Star Arms instruction are as follows:

GAS PISTON INSTALLATION INSTRUCTIONS

1.INSURE THE RIFLE IS UNLOADED AND REMOVE THE BOLT CARRIER ASSEMBLY FROM THE RIFLE.

2. REMOVE THE BOLT FROM THE CARRIER.

3. LOCATE THE 3MM DIAMETER CROSS-PIN (THE PIN SIZE MAY VARY BY COUNTRY OF ORIGIN) THAT RETAINS THE GAS PISTON TO THE CARRIER. IT MAY BE NECESSARY TO REMOVE THE FINISH FROM THE CARRIER IN ORDER TO LOCATE THE CROSS-PIN ENTRANCE AND EXIT HOLES IN THE CARRIER.

4. USE A NAIL SET OR DRIFTPUNCH TO START THE CROSS PIN MOVING AND A DRIFT PIN PUNCH TO DRIVE THE PIN THRU THE HOLE. IF EXCESSIVE FORCE IS REQUIRED TO DRIVE THE CROSS-PIN OR IF THE CROSS-PIN REFUSES TO MOVE, CENTERPUNCH ONE END OF THE CROSS-PIN AND USE A 3MM DRILL BIT TO DRILL .10" DEEP INTO THE CROSS-PIN. DRIVE THE CROSS-PIN OUT FROM THE SIDE YOU HAVE DRILLED.

NOTE: THE CROSS-PINS ARE OFTEN PEINED INTO COUNTERSUNK AREAS ON THE CARRIER. WHEN DRIVING THE CROSS PIN OUT IT IS NECESSARY TO DISPLACE THIS METAL BEFORE THE PIN WILL MOVE.

5. CHUCK A 3MM DRILL BIT INTO A DRILL PRESS AND INSERT THE BIT THRU BOTH HOLES IN THE BOLT CARRIER WITH THE BOLT CARRIER HELD LOOSELY IN A DRILL VISE. USING THE DRILL BIT TO POSITION THE BOLT CARRIER, TIGHTEN THE DRILL PRESS VICE SECURELY AGAINST THE BOLT CARRIER.

6. THREAD THE RED STAR ARMS GAS PISTON INTO THE CARRIER. IT SHOULD SCREW IN USING ONLY THE HAND. A PAIR OF PLIERS, PADDED WITH A THIN RUBBER SHEET, MAY BE REQUIRED. IN CASES IN WHICH THE FEMALE THREAD OF THE CARRIER HAS BEEN DAMAGED BY THE REMOVAL OF THE CROSS-PIN A 12MM X 1.25MM TAP SHOULD BE USED TO CHASE THE THREADS.

7. DRILL THRU THE GAS PISTON USING THE 3MM DRILL BIT ON THE SAME LOCATION AS THE TWO 3MM HOLES IN THE BOLT CARRIER.

8. INSERT A NEW 3MM CROSS-PIN INTO THE HOLE. THE CROSS PIN SHOULD BE LONGER THAN THE HOLE IS DEEP, AND EXCESS STOCK SHOULD BE POSITIONED EQUALLY ON BOTH SIDES OF THE BOLT CARRIER. USE A HAMMER AND PUNCH TO PEIN THE ENDS OF THE CROSS-PIN INTO THE COUNTERSINKS ON BOTH SIDES OF THE BOLT CARRIER HOLE. DRESS THE ENDS OF THE CROSS-PIN FLUSH WITH THE SURFACE OF THE BOLT CARRIER.

It can be a pain...good luck

If you don't want to do it you can always order one of these from Kvar. It's a US gas piston already installed in the bolt carrier.

www.k-var.com/shop/product.php?productid=16710&cat=277&page=1

It ain't cheap but it's a no hassle drop in deal.