AR Sponsor
Posted: 9/13/2011 10:37:37 PM EDT
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I know there are ballistics programs or spreadsheets that, given a bullet weight, BC, velocity, sight height, and zero distance, calculate a trajectory for you.
But suppose I'm trying to answer the following question: -I want to zero my gun for one type of ammunition (say, 5.56mm 50gr TSX) -I want to do most of my shooting with another type of ammunition (say, XM193) If I zero for the TSX, how can I calculate how high/low I will be with the XM193 at different distances? Is there a program that can do this? |
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Quoted: I know there are ballistics programs or spreadsheets that, given a bullet weight, BC, velocity, sight height, and zero distance, calculate a trajectory for you. But suppose I'm trying to answer the following question: -I want to zero my gun for one type of ammunition (say, 5.56mm 50gr TSX) -I want to do most of my shooting with another type of ammunition (say, XM193) If I zero for the TSX, how can I calculate how high/low I will be with the XM193 at different distances? Is there a program that can do this? What barrel length are we talking about? Sight Height? Muzzle Velocity? Zero Distance? Aside from BH loading it to 5.56 pressure, is there anything that the 50gr load does better than the 53gr load? |
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I know there are ballistics programs or spreadsheets that, given a bullet weight, BC, velocity, sight height, and zero distance, calculate a trajectory for you. But suppose I'm trying to answer the following question: -I want to zero my gun for one type of ammunition (say, 5.56mm 50gr TSX) -I want to do most of my shooting with another type of ammunition (say, XM193) If I zero for the TSX, how can I calculate how high/low I will be with the XM193 at different distances? Is there a program that can do this? What barrel length are we talking about? Sight Height? Muzzle Velocity? Zero Distance? Aside from BH loading it to 5.56 pressure, is there anything that the 50gr load does better than the 53gr load? Well, I was just using those two rounds as an example. My general question is that if I zero for some high-quality, expensive round (doesn't have to be TSX), and then do most of my shooting with some cheap round, how can I calculate what the difference in zero will be? |
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Quoted: Quoted: Quoted: I know there are ballistics programs or spreadsheets that, given a bullet weight, BC, velocity, sight height, and zero distance, calculate a trajectory for you. But suppose I'm trying to answer the following question: -I want to zero my gun for one type of ammunition (say, 5.56mm 50gr TSX) -I want to do most of my shooting with another type of ammunition (say, XM193) If I zero for the TSX, how can I calculate how high/low I will be with the XM193 at different distances? Is there a program that can do this? What barrel length are we talking about? Sight Height? Muzzle Velocity? Zero Distance? Aside from BH loading it to 5.56 pressure, is there anything that the 50gr load does better than the 53gr load? Well, I was just using those two rounds as an example. My general question is that if I zero for some high-quality, expensive round (doesn't have to be TSX), and then do most of my shooting with some cheap round, how can I calculate what the difference in zero will be? Buy a program that tells you, or give us the above data and we can do it for you. BTW, @ 300yds there is a ~ 0.7 MOA difference in POI between M193 and the BH TSX load. |
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I know there are ballistics programs or spreadsheets that, given a bullet weight, BC, velocity, sight height, and zero distance, calculate a trajectory for you. But suppose I'm trying to answer the following question: -I want to zero my gun for one type of ammunition (say, 5.56mm 50gr TSX) -I want to do most of my shooting with another type of ammunition (say, XM193) If I zero for the TSX, how can I calculate how high/low I will be with the XM193 at different distances? Is there a program that can do this? What barrel length are we talking about? Sight Height? Muzzle Velocity? Zero Distance? Aside from BH loading it to 5.56 pressure, is there anything that the 50gr load does better than the 53gr load? Well, I was just using those two rounds as an example. My general question is that if I zero for some high-quality, expensive round (doesn't have to be TSX), and then do most of my shooting with some cheap round, how can I calculate what the difference in zero will be? Buy a program that tells you, or give us the above data and we can do it for you. BTW, @ 300yds there is a ~ 0.7 MOA difference in POI between M193 and the BH TSX load. Thanks for that data point. I had bought this program for my phone: http://ballistic.zdziarski.com/ It has the ability to graph various projectile paths, but it's hard to tell what the real difference is from the graph, especially if they're close together. Another issue is that it requires velocity data, and sometimes I'm not sure what the velocity of a given round is. And since I have a 20'' AR and a 14.5'' AR, I need two sets of velocity data for every load. What program are you using? I might look into buying it –– I'm a numbers guy and I plan on running lots of combinations. |
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Quoted: Quoted: Quoted: Quoted: Quoted: I know there are ballistics programs or spreadsheets that, given a bullet weight, BC, velocity, sight height, and zero distance, calculate a trajectory for you. But suppose I'm trying to answer the following question: -I want to zero my gun for one type of ammunition (say, 5.56mm 50gr TSX) -I want to do most of my shooting with another type of ammunition (say, XM193) If I zero for the TSX, how can I calculate how high/low I will be with the XM193 at different distances? Is there a program that can do this? What barrel length are we talking about? Sight Height? Muzzle Velocity? Zero Distance? Aside from BH loading it to 5.56 pressure, is there anything that the 50gr load does better than the 53gr load? Well, I was just using those two rounds as an example. My general question is that if I zero for some high-quality, expensive round (doesn't have to be TSX), and then do most of my shooting with some cheap round, how can I calculate what the difference in zero will be? Buy a program that tells you, or give us the above data and we can do it for you. BTW, @ 300yds there is a ~ 0.7 MOA difference in POI between M193 and the BH TSX load. Thanks for that data point. I had bought this program for my phone: http://ballistic.zdziarski.com/ It has the ability to graph various projectile paths, but it's hard to tell what the real difference is from the graph, especially if they're close together. Another issue is that it requires velocity data, and sometimes I'm not sure what the velocity of a given round is. And since I have a 20'' AR and a 14.5'' AR, I need two sets of velocity data for every load. What program are you using? I might look into buying it –– I'm a numbers guy and I plan on running lots of combinations. No chronograph? I'm using an old program I got some guys to help me with in the 90's. It works out to 1000yds. I forgot to tell the guys who wrote to include ranges past that distance because it did not occur to me.  |
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Quoted:
I know there are ballistics programs or spreadsheets that, given a bullet weight, BC, velocity, sight height, and zero distance, calculate a trajectory for you. But suppose I'm trying to answer the following question: -I want to zero my gun for one type of ammunition (say, 5.56mm 50gr TSX) -I want to do most of my shooting with another type of ammunition (say, XM193) If I zero for the TSX, how can I calculate how high/low I will be with the XM193 at different distances? Is there a program that can do this? You'll just have to try your loads and see where they hit, and then you can make your adjustments as needed. You may get lucky - sometimes different loads can hit very close together at 100yds, close enough that it may not matter much for your purposes. But there is no program that will tell you this ahead of time. This is an interior ballistics problem, not an exterior ballistics problem - in your scenario the bullet trajectories have surprisingly little to do with where the bullets actually hit. As the bullet and powder starts moving down the barrel, the rifle is recoiling around it, and the barrel is ringing and whipping around. By the time the bullet leaves the barrel, the muzzle isn't pointing in the same direction as it was when you pulled the trigger. As long as it recoils and rings the same way each shot you are ok, all this is taken into account when you sight in the rifle. But when you put a different type of ammunition on the rifle (sometimes even a different brand with the same bullet weight) there's no good way to predict how the rifle will recoil and the barrel will ring, so there's no way to predict how the impact point will change between the two loads. Often times a heavier/slower bullet will hit higher on the target than the lighter/faster bullet, because the slower MV means it was in the barrel longer, so the rifle had time to recoil a little higher before the bullet left the barrel. Sometimes the impact point will even be off to the left or right. Even with the same bullet weight this can happen, I've got an old Colt SP1 (pencil barrel) that can place different 55gr loads many inches apart at 100yds. |
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Good info's been shared already. I have the same issue, because I zero it for my hunting round but shoot all kinds of ammo. If I'm using the scope I make notes & adjust accordingly; my scope has a zero reset so that's my hunting baseline and everything else gets adjusted. For iron sets, eh.....with my 44 year old eyeballs most of the difference between rounds gets lost in the fuzzys. At self defense ranges it won't matter anyway.
One thing I was surprised to see was similar rounds differing in windage. I zeroed with a 75gr OTM Black Hills at 50 yards, and 75gr TAP training shot consistently 3/4" to the right. Elevation difference I expected, but not windage. Whatever your zero is, don't trust it with any other round, no matter how similar, until you confirm it. |
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Quoted: Sometimes the impact point will even be off to the left or right. Even with the same bullet weight this can happen, I've got an old Colt SP1 (pencil barrel) that can place different 55gr loads many inches apart at 100yds. This is why the ballistics programs can only go so far. You really need to get out there and shoot. |
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