I've taken 4 whitetail deer with mine.
I used Speer and Hornady bullets with handloads.
Two deer were taken with Speer 120gr HotCore soft points. One has been taken with the Speer 140gr PtSpt "HotCore" and one with the Remington/Hornady "Accutip" 120gr version of the Hornady SST.
Performance was indistinguishable from the .257Roberts or .270win.
Accuracy is all that you can expect from a 6.5lb factory barrel/rifle. It will occasionally shoot 3-shots touching at 100yds. A bit more accurate than my nearly identical rifle in 7mm08, but not quite as effective on deer.... The 7mm has a slightly wider wound cavity. Deer are small enough that penetration is indeterminable as most bullets completely penetrate. I have recovered one bullet from the .260. It was a Speer 120gr that hit the front shoulder and was lodged in the pelvis area of the deer. Expansion was to ~.750" and retained weight was 94gr. Or, again about like the .257Roberts or .270win. At the velocities of the .260 (2,850fps w/120gr bullet, 2,700fps with 140, the so-called "legendary penetration" isn't going to happen with bullets that open and expand reliably. Expansion precludes penetration...
With some Sierra 160gr RN that I've got a splendidly accurate load with at ~2,400fps, You "might" see the so-called penetration. However, you better place that shot very, very precisely, or the game will depart to relms unknown, just like anyother deep penetrating/low expansion bullet.
I like the .260 and the rifle it's in.
But, it ain't a .30/06 or .257wbyMag.
It dosen't have the laser-beam trajectory of the .257 with 100-115gr bullets; nor the wider wound chanel with similar penetration/trajectory of the .30/06.
But, thats what puts it and it's older sibling the 6.5x55 in a unique category.
BTW; IMO, it's head and shoulders above a .243 for medium game, which is it's "niche", anyhow.... No real suprises. Just a mild, capable game killer, with a decent bullet and "reasonable" shot placement. Just no "MAGIC" or such.