My dad has been shooting 180gr winchester cxp2 out of his .308 and he likes how they perform on deer. I have been reloading and have a box of 180gr sierra game king sp bt bullets. Would these 2 bullets preform similar?

Stick a 180gr Sierra GK in a reasonable spot and you've got a dead deer. I'm not familar with the winchester bullet.

remember your shooting deer, not elk or moose.
just about any good sp will kill deer. thats about all i use 90% of the time is SIERRA

PH's in S Africa told me that the 250 gr Game King out of a .375 would just disintegrate on African game. Moving around 2820 fps, I only recovered 2 of em, 1 out of an Eland and 1 out of a Kudu. The one out of the Kudu was a perfect mushroom and retained 78% of it's weight and same results with the Eland with 77% of it's weight. I like them. Can't say on the winchester bullet, never tried it. The Sierra will do just fine.

I have used the 180gr Win cxp2 for many years successfully on Kudu, Gemsbok and Rooibok. As always its correct bullet placement that's important. My 308 gives me better groupings with Sierra gk's but I have yet to hunt with them.

I use sierras quite a bit. I have yet to have one work differently than expected. Placement is key with anything and honestly I can't imagine being able to tell them apart from each other on game.