I bought a 930 tactical today at a gun show brand new in the box. It is the one with the door breacher and from what I am hearing a 4 round tube capacity. My question is I went to load it tonight and I can only get 2 rounds of 2 3/4 shells in it. I think there is a plug in the tube. I saw you can buy the 6+1 tube extension from Choate. How would I install it or how do I get the plug out of the tube? I stripped the gun down and it does not look like the tube can be just taken out. Is there a safe way of doing this without ruining the gun?