The latest Hornady handbook, #9, lists the max load for the 139 grain SST and RL-19 in the 7mm WSM at 71.0 grains which produces 3,300 fps out of their 24 inch Model 70. You have two more inches of barrel which will add some velocity. If you take that into account along with the possiblity of a faster burn rate on your powder and the effect of your custom Brux barrel, I can see how you could get the velocities you mentioned. Of course the comments made about chronographs not reading correctly are also valid.
To give you another data point regarding Brux barrels, I have a 7mm WSM in a 28 inch Brux with a 1 in 9 twist. I had it custom throated for the Barnes 168 grain LRX. That bullet is actually longer than the 180 grain Berger so the COAL is 3.165". This gives me 10 more grains of powder capacity than if I left it per SAAMI. I'm getting 3,157 fps with that bullet using 76.6 grains of Magnum. The muzzle engergy of that load is 3,718 ft lbs. Pressure is probably around 63,000 psi so that is about all I can get out of it. That isn't very far behind a stock 7mm RUM which shows what you can do with a good barrel and a bit of custom gunsmithing.