I recently picked up a bunch of these that weigh in at 145 grains. They look to be very uniform. Swift only shows 140 or 150 grain in their catalog. Anyone have any idea as to why these would be "mid-weight?" Have yet to shoot any, but hope to get out this weekend.

Did you re-zero your scale and test it with the test weight and weight the bullet? If not Zero the scale and weigh it again. If you get the same results I can't answer why you have some that weigh 145 gr. The 140 would be a split the difference weight because the usual weights for the 270 are 130 and 150 grains. A few years back the 140 grain bullets came out as a 'happy medium' with several bullet companies.