How to transfer 3.5 million records from one Access 2010 table to another

Because my table has over 3.5 million records I'm having issues with changing the data type in certain fields in the original table (Table A). Since it's so big I can't simply copy and paste the entire table and if I went with the 65,000 record limit, I'd have to do it 54 times, which I'd rather not do. I created a "Copy of A" (structure only), fixed the data type and tried an append query, but that didn't work either. It couldn't open the table. Anyone have any suggestions?