I am using a muzzle loader for deer and I have been using a 260 gr. winchester supreme bullet. It is doing the trick, but I was wondering what everyones opinion was on muzzle loader bullets for deer. Which ones put them down the best. All my shots are under 125 yards.

I shot my first muzzleloader deer this year using a 300 grain Hornady SST ahead of two 50 grain 777 pellets. The shot was not that far, most of mine aren't. Quartering shot, entered inside deers right shoulder and exited through last ribs on the left side. Deer traveled about 20 yards after the shot. I bought the gun this fall and did not get the chance to try too many different loads. This load shoots two inches at 100 yards. TTS

One thing to look on sabots is the sabot itself tearing or being deformed. That will destroy your accuracy.
I personally like the Barnes MZ, as I have never had one tear, in spite of shooting magnum loads and firing 10 or more shots without cleaning.
If you use sabots at all, look for them when the shooting is over. If they are deformed at all, find another bullet.

Do you think that I should go with a heavier bullet than the 260 gr.? Or is this OK.

I forgot to mention, I am shooting a .50 cal. and I am using 120 gr. powder.

For deer the 260's well work fine. If you shoot them in the right place you well have no trouble. If they are accurate use them with out any trouble.

I like the 410 grain flat-base hollow-point Buffalo Bullet with 100 grains of Goex FFg in my T/C New Englander.

Of course, I'm pretty sure that's not what you're looking for.

I like the 250 Gr. MZ using 3 50 Gr. Pyrodex pellets. This gives me around 2100 fps.
Unless your after something larger than a deer, a 260 gr. bullet should be fine.