I have had fantastic results with the 3 inch Federal Premium Truball Rifled 1 oz. They run great thru my 930 SPX. I have to say I have had great results with this gun. Running OR3GUN's "Follower" with a Wolff spring as well.
LOL. Glad to hear you got it to cooperate finally. it's a bad a$$ gun no doubt. I love mine, blows the chit out of anything standing in front of it. Just something about emptying a magazine of 6 slugs in a matter of a couple seconds.
Here is the part number for the Boron Nitride (Pro Series) magazine tube from Mossberg:
16801BN MAGTUBE 930/935,BORON-NITRIDE
They were about $35.00 at last check.
William
http://www.OR3GUN.com