100 grain bullets in a .257 Roberts is all one needs for deer and pronghorns.....the 120 grainers are good as well but 100 will do fine. Ive used the interlocks from Hornady with good success for years but the Swift A-Frame is a superb bullet and almost the best you can find IMO. The "buck-a-piece" pricing of the A-frames is minor if you don't do your practicing and varminting with the A-Frames. I use them in many of my guns and a box of 50 is nearly a lifetime supply as I usually only shoot a couple a year.

The first box is used to verify the accuracy and that one is not cheap as you shoot them all doing load developement. After that however I still have loads for a .300 H&H that I loaded (box of 50) six years ago and expect them to still be used for hunting another ten years.

In other words.....make them last and they're really not expensive at all.

Deer however are easily killed and personally in such guns as the Roberts, I'm still shooting 100 grain winchester silver tips and Hornady interlocks.