Ballistic Apps

I might should have posted this thread in another section, but I didn't. Since I have XP-100's that I intend to shoot at distance, I figured I'd start here. I have shot two of my XP-100's, both 30 Nosler, at 400 yds, and still need to confirm the data on those two.

I did a little more shooting at 400 yds with a couple different guns this past weekend. 300 RUM and 28 Nosler.

I shot one shot each for zero confirmation at 100 yds. 300 RUM was between 0.750"-1.00" high. 28 Nosler was just under 0.500" high.

300 RUM called for 3.5 MOA up (Berger 215 @ 3174 fps). 3.5 MOA put the bullet nearly spot on. My left/right at my 100 yd zero was ~0.25" right, and is reflected, I think, in the 400 yd impacts. I did not account for the left right on purpose.

28 Nosler was an experiment as I don't know the BC of the Matrix 175 VLD bullet (3028 fps) I'm using (only have about 200 of these). So, I started at 3 MOA up as I expected the bullet to be low and I knew I would capture that on the paper target I was shooting at. It was right at 7.5" low for a 3-shot group that measured under 1/2 MOA.

I guessed at a BC of 0.336 and dialed 4.5 mo up. I then smacked a 4" steel swinging target.

Seems my problems prior are exacerbated by using a negative number on the zero. Hornady podcast as well as Kestrel podcast support this.

At any rate, I may be well on my way to learning how to use my tools.
 

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One of the easiest errors to make in any BA is pressure. Depending on what you are using it's confusing as best. Barometric Pressure, if it's the input will need to have an altitude or elevation associated with it. This will allow the program to use the correct station pressure. If the program asks for station or actual pressure then the actual station pressure should be used. 4DOF requires Barometric pressure and altitude. If the station pressure in lieu of Barometric is used the altitude should be zero.
 
I didn't read the whole thread so I hope I'm not repeating someone else, but you said that you were using a Chrony. I have 1 and like it, but if you look at the joint where the upper and lower sections join and have silver plates to adjust the relationship between the upper and lower sections when open. It doesn't take much misalignment to change your velosity reading. I would try another chronograph and compare the results. Do the comparison as closely together time and condition wise. I found a problem one time when I didn't get mine open completely. It showed quite a bit of difference from my norms until I found the problem. Just a wag, good luck Paul
 
scpaul said:
I didn't read the whole thread so I hope I'm not repeating someone else, but you said that you were using a Chrony. I have 1 and like it, but if you look at the joint where the upper and lower sections join and have silver plates to adjust the relationship between the upper and lower sections when open. It doesn't take much misalignment to change your velosity reading. I would try another chronograph and compare the results. Do the comparison as closely together time and condition wise. I found a problem one time when I didn't get mine open completely. It showed quite a bit of difference from my norms until I found the problem. Just a wag, good luck Paul
Click to expand...
I've ran two Chrony's back to back. Gave virtually same readings. I always make sure mine are open all the way as well as line up correctly and parallel to line of sight path, as these can influence the reading.

I've ascertained that my zero input wasn't as precise as needed and also that whatever reason, the apps appear to not like a negative zero (even though it shouldn't matter).
 
Buttermilk said:
I've ran two Chrony's back to back. Gave virtually same readings. I always make sure mine are open all the way as well as line up correctly and parallel to line of sight path, as these can influence the reading.

I've ascertained that my zero input wasn't as precise as needed and also that whatever reason, the apps appear to not like a negative zero (even though it shouldn't matter).
Click to expand...
I might try another brand/style of chronograph. I don't have any idea why it would have any effect but you are looking for "needles". Stupid question, you have re-confirmed the target distances and made sure that muzzle air turbulance isnt affecting your readings. You might try shooting without the rods in place. I realize that that shouldn't have any effect since the point of discharge and discrepancy are the same. Have you tried the same tests with another caliber. I'm just trying to get you to try really crazy things since it appears that you seem to have covered all the logical bases.
Good luck, I'm looking forward to you finding the problem cause I'd like to know too, Paul
 
scpaul said:
I might try another brand/style of chronograph. I don't have any idea why it would have any effect but you are looking for "needles". Stupid question, you have re-confirmed the target distances and made sure that muzzle air turbulance isnt affecting your readings. You might try shooting without the rods in place. I realize that that shouldn't have any effect since the point of discharge and discrepancy are the same. Have you tried the same tests with another caliber. I'm just trying to get you to try really crazy things since it appears that you seem to have covered all the logical bases.
Good luck, I'm looking forward to you finding the problem cause I'd like to know too, Paul
Click to expand...
I've already figured out my issue. Wasn't the chronograph…
 

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