I was somewhat surprized by the results also. Some of the difference is the fact that I have a 26" barrel, my friend uses almost the exact load (.5gr more powder) and only gets about 3200 to 3250 out of his 24" barrel. I am seating the bullet .030" off the lands, I have to because at .010" off the lands the cartridge will not fit into the magazine. I'm also using fire formed cases neck sized only to get the max capacity of the case. Set up this way the cases will hold almost 80gr of 7828 to the bottom of the neck. The bullet is seated such that the boat tail is the only thing below the neck which gives me around 95% loading density. In my gun I started getting pressure signs at 72gr on warm days (I always work up loads to check for pressure on warm days) so 71.5 is what I consider max during the colder days of hunting season. The load shot well at .5gr above and below this but really shines where I have it.

BTW,when I first worked up this loadIMR had on the web site a 140gr load using 72gr of 7828 as max but they have removed it since then.

The other thing to remember is that each rifle is an individual and may react differently than the test barrels used for the loads listed in the manuals. This is why manuals from different companies often have different max loads, sometimes several grains of powder different. So work up each load carefully and consult more than one manual to ensure your in the safe zone.

I hope this answered your question. Be safe and enjoy the art of customized loads for your gun.