bludog,
The big difference I'm seeing is you used 140 Nosler Ballistic Tips with RL-16, and Alliant's data was shot with 140 Nosler Partitions.
Partitions are well-known for producing more pressure (and hence velocity) than other bullets of the same weight, including Ballistic Tips. In fact, as noted in one of my earlier posts, I've seen two bullets of the same weight, in the same cartridge, with the same powder charge, result in 250 fps difference in muzzle velocity.
The rifle was a Model 70 Winchester belonging to a friend, factory-chambered for the .270 Weatherby Magnum. I don't remember what the powder was, but at that time the Hornady manual listed the maximum charge as getting 3400 fps with the 130 Hornady Interlock Spire Point, and he'd worked up to that point with no problems.
At that time my buddy didn't own a chronograph, so one day we shot his Interlock handloads over mine, and they did get just about 3400. He then said he'd loaded some 130 Partitions too, and wanted to try them. They got around 3650 fps--with the same brass, primer and powder charge.
Before passing judgment on Alliant's data you might want to try the same load with the same bullet they used.
