Have a Colt 20" Sporter which appears to have a fired primer jammed into the gas key; but definitely has some type of metalic looking obstruction in the key.

Any suggestions on how to remove this with a minimum of work? I'd prefer not to remove the key if possible.

Currently considering using a small drill bit to pierce the obstruction and pull it out the front of the key; but concerned that the gas pressure fed into the key might have "spot welded" it into place.

If it were mine, I would first try this.  Take bolt, firing pin, etc off carrier.  Lube up the gas key well with penetrating oil, put on safty glasses.  Then get out the air hose, plug as many orafaces as possible, leaving one for the blow gun, the other the gaskey opening.

Put the shop air to it and see if it blows out.

Next, the drill it out you mentioned.

All elae fails, take the key off, clear it (or replace if necessary) and re-install with new screws.

Of course you could always sell it on ebay as a "rare, tactical single shot sniper carrier".

3 gallon bucket and a rubber mallet.

Insert the B/C buffer side down with the bolt straight up.  Fill the bucket until the water comes to the the top of just the carrier.  Pull the bolt all the way up, then use the rubber mallet to drive the bolt back down/closed.

If you can't get the part out this way, then just pull the key and just use a piece of wire to drive the parts out of the key.

The hydraulic method is definitely cool. The method will produce with way more pressure than the air compressor can come up with.