* Fortescue Q3 shipments drop 6 pct
* Blames bad weather for fall
* Full-yr guidance intact (Adds iron ore market prices, outlook, Fortescue costs, paragraphs 2-4)
By James Regan
SYDNEY, April 13 (Reuters) - World No. 4 iron ore miner Fortescue Metals Group reported a 6 percent fall in third-quarter shipments on Thursday but said it was still headed for a bumper year.
Fortescue Chief Executive Nev Power reiterated company guidance to ship between 165 million and 170 million tonnes of iron ore in the year to June 30, most bound for Chinese steel mills.
The Australian miner's cash production costs stood at $13.06 per tonne in the March quarter, a 4 percent rise over the previous quarter owing to weather-related shipping disruptions but still well under market prices.
Fortescue shipped 39.6 million tonnes in the quarter to March 31 versus 42.2 million tonnes the previous quarter, according to its latest operations report.
Facing oversupply and waning demand from top importer China, iron ore has swung into a bear market with the price off more than 20 percent from its February high due to concerns of a looming supply glut.
The Metal Bulletin-quoted price dropped $6.34 on Wednesday to $68.04 per tonne, its biggest one-day percentage drop in 13 months .IO62-CNO=MB. (Reporting by James Regan; Editing by Stephen Coates)