I spotted a 1903 converted to a .30 Gibbs today in a local gunshop. Anyone know much about this one? What is it compared to as far as ballistics?

The 30 gibbs is a 30-06 case with the shoulder moved forward and re-shaped to 35 degrees. Minimum case taper and a very short neck (on the order of .250"). Rocky Gibbs wasn't happy with the Ackley Improved cartridges, so he built his own with the differances that he thought meade a better cartridge. He also went with forward ignition on his cartridges, but I'm not aware of anyone doing that today. They just use regular cases. There is a little more work to forming the cases, but you get a little more velocity (then with the 30-06 AI). I have Gibbs rifles in 7mm and 240, they work quite well and deliver as mentioned. It doesn't turn your -06 into a 300 mag (although it will equal factory 300 H & H loads), but it gives you a little more velocity to play with. FWIW - Dan