I don't usually comment on "is it enough" because I tend to believe that if you have to ask you may already be doubting the question and when you have bambi in your sights you can worry about many things but having enough gun/bow/spear should not be one of them.
I have successfully taken three deer with my 38 caliber shooting roundball. And yes that is only a 79 grain ball (.375) being pushed with 40 grains of FFF real black.
BUT, and it's a giant but, I primarly hunt deer with bow. So my shooting lanes "do not" extend beyond 35 yards - can't see further than that so no chance of "trying" a shot beyond that.
At 35 yards my velocity is about 1475 fps with an impact of about 350 foot pounds.
AND because of that it MUST BE a full on, standing still BROADSIDE shot right through the heart lungs. No quartering shots, no shots on alert deer, no contorting out of the stand - If I wouldn't take the shot with my recurve bow, I won't take the shot with my 38.
So I "know" a 40 is more than enough if you only take a near perfect shot. If you "just have to get a deer" a 45 or better is probably more what you need.
That’s the way I look at it. What are your shooting conditions? Do you see a lot of deer? Human nature is impulsive. A hunter 8 days in without seeing much will be tempted to take a less than ideal shot. A deer that’s walking or quartering away at 40 yards. I don’t take that shot with a .40. With my .58, probably so. Pretty confident with .50 and over.