I would have thought that 50grs. was not enough. My first longrifle was (still have it) a traditions Pennsylvania Longrifle. It is actually most accurate with a 95gr. load, which is a heavy load. On the other hand, my Early Lancaster rifle by a private builder is most accurate with an 80gr. load. I've taken deer with both. If your rifle is accurate with that little, you should be fine up to about 50-yards. 75-yards will be stretching it a bit and shot placement will be key.
Have you worked up a load yet to find out what your gun is most accurate with? If not, you need to do that because just about every gun is different. If you still have the adjustable ramp rear sight on your rifle, take 3 to 5 shots at 25-yds at a target using your 50gr load. Don't worry about high or low, you want to get left or right fixed first. Ideally you should be a little high here. Once you have it on paper, measure the spread and jot it down.
Next go put the target at 50-yards and repeat. The pattern should be significantly wider at this point. Now raise up your charge in 5gr. steps firing at least 3 shots with each increase in load until your pattern gets smaller. Take notes at each step up. You will get to a point where that next 5gr increase in load opens up your pattern a bit. If you see that happening, make sure you repeat that same load with 3 more shots. Continue a couple of steps past that to see if it continues to open up the pattern. If so, make a note on how much you varied the pattern with 10gr. over your best load. So now you will know what your most accurate load is and also how much less accurate 10gr. above that load will be.
Finally set the target at either 75-yards or 100-yards. This is where you want to make your final sighting adjustments. You do need to be sure to take your shots when the wind isn't blowing because it will move your lead ball at these ranges. Adjust your sights using a bench rest until you're getting the spread on or around the bullseye. If you zero this for 75-yards, and get a decent spread, you're done for now. Make a powder measure that holds that amount of powder and go hunting. If you zero this at 100-yards and the spread has opened up significantly from the 50-yard spread, you may need to increase your load to tighten it up. You may also need to raise your rear site more to get it to the bullesye. Again, do the increase in 5gr. increments and see where that takes you. Don't be surprised if your most accurate load at 100-yards is another 10-grs. higher than at 50-yds.
You know that the path of the bullet will be in an arc because you can't fight gravity. If you are zeroed at 100-yards you will typically shoot low until you get to 25-yards, be high at 50-yards and usually highest at ~60-yds; and finally dead on with the point of impact (POI) matching the point of aim (POA) at 100yards.
How much low or high you are is going to depend upon your muzzle velocity. Below are a couple of charts where I presume you are getting 1,500 and 2,000 feet-per-second muzzle velocity. Below that I've done a 100-yard zero with both 2,000 and 2,200-fps muzzle velocities.
Here's a table showing 75-yard zero with a starting muzzle speed of 1,500-fps.
If you can reach 1,500fps with your load and you zero at 75-yards, the greatest deviation from your Point Of Aim will be 1.7" high between 39 and 49-yds. However, if you take a 100-yard shot that shot will end up 4.2 inches low at 100-yds.
Now lets see it at 2,000fps:
At 2,000 fps it will be off by just 1" high between 44 and 52-yds. That higher speed makes a big difference. There's less drop of the ball because it gets there faster.
Now looks at zero at 100-yards with a muzzle velocity of 2,000fps:
This will be dead-on of course at 100-yards but the biggest deviation is shooting 2.6" High between 54 and 64-yds. and then 2.5" low out at 115-yards.
If you can get the speed up to 2,200 feet zeroed in at 100-yards, you'll get the deviation down to just over 2" (2.1") out to almost 115-yards, which is considered a very flat trajectory for 100-yds..
So I would suggest find the loads that are most acurrate with your rifle first and then find out what your fps is with that load. Once you have that info it's a lot easier to figure out how much that most accurate load deviates from the point of aim at various distances. So the next thing you might want to do is find someone with a chronograph to see what your initial muzzle velocity is.
From the various ballistics I've run, if you really will only have a 75-yard shot at the longest, you should be able to reach that 1500fps muzzle velocity and have just a 1.7" deviation in the path of the ball. If you can get it up to 2,000-fps with a 75-yard zero, that's just an inch above POA - a very flat trajectory.