RE. Current Data for W748/W760
Lyman 49th Ed. was the only source I found listing both mininum and max. loads for W748 in 300 Savage for 180 gr. bullet. Appears to be based on older lot of powder, 37.5 @ 2181 fps. to 41.7 @ 2480 fps.
Hodgdon list one load only, 38.8 @ 2350 fps. as maxinum. I found the same limited information in the Hodgdon 2010 Reloading magazine manual. Apparently the 300 Savage is passe in 2012. The 300 AAC and 30 AR apparently being more popular. I digress ...
My original suspicion that very little published data exsist for either W748 or W760 powders appears to be correct. Speer do mention one load for W760 for the 300 Savage on their website.
As far as something being amiss with the Model 99 barrel or chamber, the firearm is in excellent condition. The bullet is from a trusted lot #. Ditto primer and OAL.
It would have to be a monsterously copper fouled barrel to cause pressures high enough to sevearly stick cases with what had been a very good load. We live in Nova Scotia, so the spring temperatures would be in the 60 to 70 F. on a very warm day.
The only varible appears to be the change in powder lots of W748.