Jay,
I have two personal rifles I have only just recieved from the U.S which will become my new back-up rifles on our buffalo hunts.
Both have been made to wear N.E.C.G open sights.
My previous back-up rifle (a CZ 550 in 458 Lott) was also used with open sights but not the original CZ offering which, I agree with Ses's evaluation in that they are inadequate.
The original CZ front pin is miniscule and even with my 20/20 vision it is difficult to pick up in all but the best light.
I replaced the original with a bright custom made 2mm brass pin which worked like a charm in ANY light.
The level of success you obtain from your intended use of open sights will be dictated by several factors.
*the type of terrain you are hunting;
*the time of season you are hunting;
*your willingness to forgo/pass on the long shot.
(not withstanding your profficiency level with opens).
Now let me explain.
I hunt and excessivley large and varied concession.
Within that area the terrain and flora varies considerably, but to a large extent, because of our coastal proximity, most of our hunting areas are quite thick. In addition to the scrub numerous termite mounds and other obsticles make it quite reasonable, MOST OF THE TIME, to expect to be able to aproach buffalo to within 70yds or less.
A great majority of our buffalo are taken at less than 50yds.
Perfectly doable with open sights if you have good quality open sights and have become profficient with them.
This does change as the season progresses in the Northern Tropics of Australia.
From August onwards ground cover diminishes and the bush begins to rapidly dry out and thin down. Watering and feeding sources for the animals have diminished and therefore small family groups join up into slightly larger heards. More eyes, more ears.
By September, which is an awesome time to target big bulls, herds numbering 40 or more are not uncommon. They are more stressed than earlier in the season as they are now constantly travelling to find their requirements and shots on animals at close range are MUCH more challenging to acheive (not impossible, just more difficult).
SOMEtimes in SOME areas under SOME circumstances that once in a lifetime 110" bull may be spotted in an opening, at 150yds, being alerted to your presence after picking up your scent on a swirling current. Now a lot of Dg hunters will refuse to take such a distant shot at big game weather their rifle is scoped or not and I personally applaud and endorse that thinking. If you are of like mind then no issues.
Personally I believe a mild shooting rifle chambered in .375 benefits greatly from a quality scope in providing the optical detail to be able to position shot placement precisely.
In saying that, if you were specifically focused on limiting shots to say 80yds and under and are profficient with opens at this distance then I'd say go for it, but be prepared to live with the limitations that this set-up brings.
Good hunting, I hope you enjoy your experience hunting buffalo in Australia and I hope you bag a great bull.
Paul.