How much grass or leaves would it take for you to pass up a shot on a buffalo? For exsmple,
at 50 yards would it take a bush halfway between? Thin grass? Grass thick enough to blur a target?

To me its a question difficult to answer in general terms. Each situation would be judged at that moment of time.

In general if thepoint I want my bullet to hit was obscured by anything then I would have to pass. If I could not see my point of impact on animal at all no shot. For example if a clump of grass was blocking the vitals but I thought the round I was shooting would punch right through the grass I still do not know if another animal or stump or other object might be in the way, so no shot.

In short, IMHO, it depends on the situation.

Of course, there is always the simple fact of the circumstances where you have no choice but to set up and fire -like where he is at maybe,35 yards, and swinging towards you and giving the traditional look.I rather suspect that few shooters are thinking about how good a trophy he might be. As the Spaniards say, it's "la hora de verdad". Time freezes and there is nothing but you, a hunter and him. Enjoy.

I was brought up to never shoot unless I had a clear view of my target, and what's behind it. That applied to everything from BB guns to big bores. Over 40 years of hunting, I have tried to hold to that tenet. There may have been a time or two that I wavered a bit, but not many.

I have asked several PH's about the use of solids on African game, and the amount of brush in front of an animal before avoiding a shot. Almost universally, they have felt that grass or brush inside of 6 feet was OK, and further out from the animal, you should wait for a better chance. So far, I haven't had to risk it.

I think a lot should depend on if the animal is a dangerous game or a plains game. I wouldn't want to chance a shot through a lot of brush if the animal was dangerous and a wounding shot was given. I shot an Impala thru a lot of brush and it worked out fine, but I wouldn't try it on a buffalo if I could avoid it. This is what I shot thru for the Impala.

I don't shoot through bush, etc that I see period. Sometimes there are small twigs, grass, etc that you don't see through the scope or naked eye. Take a picture sometime at a low elevation and you may see grass in the picture that you never noticed while just looking at something. During the normal course of events this is not enough to through a shot off though. I had a Blue Wildebeest standing straight on behind a small acacia this year in S.A. and told my ph that I didn't want to shoot through brush. He agreed and we just waited (seemed to me like five minutes, but was probably only 30 seconds) until he moved a few feet to the side and faced us again. One shot later and he was headed for the salt. Should have the mount back in a few Months.
Just have patience and things work out. If not on that shot opportunity, it will the next.
I don't like taking the chance of wounding animals large or small.

Wise responses, all.
I remember about 25 years ago I faced a buffalo with only grass between he and us at about 20-25 yards. I wouldn't shoot because there was only a blurred silouette. We waited 20 seconds or so, the buffalo trotted off, and the local tracker was hopping mad that I didn't shoot (this was a local affair, no outfitter, no PH). But the tracker didn't quit on us. Three hours later we caught up to that buffalo in a mud bath in a dry creek and dropped him. In this first situation I wouldn't shoot because there was no guarantee of immobilization and the distance was too close to 'start something'. A heart shot could have allowed the buffalo to charge and kill someone. If he charged I would have shot, but not until.
The question came up because while sighting in a rifle last month I got a full sideways keyhole from a very stable 416. Obviously one of the little branches in the flight path hadn't been trampled down enough. And it reminded me about how things can 'go south', (or 'north' if below the equator), meaning 'go awry'.

Thin grass.

Buliwyf
Are you saying that a stalk of thin grass (3 to 6ft tall, of course) can start a 350 grain projectile tumbling end over end?

Probably one leaf is less diversive, maybe not much more than a cardboard target.

If the animal is not visable enough to be positive of a killing shot, I pass. I have and do take a shot in 'holes' in the brush.