I've had my mark 3 for about a year now and nothing Ive tried will stop it from rusting just yesterday I took it out of the case and found 5 or so spots of rust. Its been in the case for a month or so and was cleaned and oiled before I put it up.

Its the bull barrel standard blue mark 3. Anyone else have trouble with rust in yours? If so how did you stop it?

If you have a chronic rust problem not attributed to how or where you store it, the surface may be contaminated with salt or corrosive residue that is not being cleaned off with standard cleaning solvents and oil.

Try detail cleaning the gun and wash all the parts in warm soapy water, rinse in warm water, then rinse again in a 50/50 mix of Ballistol and distilled water. Dry with compressed air and/or low heat and then lube as normal and reassemble.

I have used this method to decontaminate guns that have been exposed to salt water spray and nasty stuff

just like never storing rifles in cases, you should never store pistols in a foam case or holster. leave them open to air, or in a hard case without foam.