Requested: ballistics calculation when modifying shot angle

lince

Hi all!.
DallanC: I made a suggestion some time ago (see here), and I have another suggestion to include in new release:
Usually you perform calculations and sight adjustments taking into account that shots are done (almost) horizontally. In other words, the rifle and sight are at the same height that the target.
But ballistics can change when you have adjusted your sight in that conditions and you have to shot with some elevation (very usual when hunting in real conditions).
So my suggestion is to perform a calculation from a load/sight adjustment when the shot is done with some positive or negative elevation.
Could it be possible?.
By the way, thanks for your work!.
/lince
P.S.: do you have some plans about next release date?. I'm sure it'll be really impressive and I am really impatient for it Smile

popgun

Hi Lince,
Dallan will answer your post when he logs on later. As for the release date...shucks man it's hunting season and Dallan is a true hunting nut. I'm suprised that he has worked on it as much as he has this season. But the short answer is when it's done to his satisfaction he will release it. We are still in testing and he is working on the printing functions and format of some outputs but the final version will not be released for a while yet. Yes it is a work in progress and we come up with changes in the middle of the process. One change I suggested took two weeks to write then test for bugs. It's just a slow process so stick with us.

DallanC · Site Admin Joined: Jan 18, 2005 Posts: 3572 Location: Utah

lince wrote:

Usually you perform calculations and sight adjustments taking into account that shots are done (almost) horizontally. In other words, the rifle and sight are at the same height that the target.
But ballistics can change when you have adjusted your sight in that conditions and you have to shot with some elevation (very usual when hunting in real conditions).

The new version already has angled calculations included. You sight in your rifle on a horizonal field at a specific distance, this gives you your trajectory. The new version of pointblank has an additional field called "Angle" and you can input any angle from 0 to 80 degrees and it will give you data on how high or low your bullet is with respect to line of sight at that range, based on the horizonal "zero" range. Its cool stuff.

Quote::

So my suggestion is to perform a calculation from a load/sight adjustment when the shot is done with some positive or negative elevation.
Could it be possible?.
By the way, thanks for your work!.
/lince

You lost me on the "load / sight adjustment". Are you adjusting it in the field?

Quote::

P.S.: do you have some plans about next release date?. I'm sure it'll be really impressive and I am really impatient for it Smile

Lots of people are. Its been a much larger project than I intended from the beginning. Its also in a new programming language I've had to learn. Most of it is up and workign right now and I'm currently working on the Printing system.

I havent had much time to work on it lately I fear, hunting season took up some of my time but more of it is work as usually and getting honey do's done around the house before winter truely sets in (I spent yesterday for example putting up all new raingutters around my house).

-DallanC

djwarner · Rookie Member Joined: Dec 23, 2009 Posts: 10

I'm having problems with the ANGLE factor in the online version. I see that the input is limited to less than 89 degrees. But the affects on the trajectory looks incorrect. Using a Federal 30-30 150gr @ 2390 Fps at 79 degrees, the max height is only a few inches compared to an angle of zero.

Also, Hornady 30-30 Leverevolution is supposed to be a low BC compared to the Federal 150 gr FN. Both give sighting data on the box. Trying to duplicate their trajectories requires nearly identical BCs. I think someone is exaggerating?

My set-up - Marlin 336 with scope height of 1.94 inches, temperature and altitude set to default.

Info on the boxes:

Hornaday 160gr FTX - Muzzle 2400 fps, 100yds +3.0", 200 yds +0.2", 300 yds -12.1"

Federal 150gr soft point FN - Muzzle 2390 fps, 100yds +0", 200 yds -7.2", 300 yds -26.7"

Both of these require a BC of about .189 to match the listed results which I find odd.

If I sight in the gun for one how do I maintain this to estimate the performance of the other? Shocked

DallanC · Site Admin Joined: Jan 18, 2005 Posts: 3572 Location: Utah

I've never been able to achieve factory drop values with their loads. Always do your own shooting. Barrel lengths vary, velocites vary... elevation, temp... it all varies.

Shoot any ammo over a crono and take it from there. I've always said if people want to know what their drop is at 300 yards, they need to shoot at 300 yards Smile

Anyway I'll look into the online calculation soon. Been super busy at work (12 hour days, 6 days a week).

-DallanC

chambered221

DallanC wrote:

Shoot any ammo over a crono and take it from there.

I have never seen factory listed velocities match shooting over a chronograph !!!
I wouldn't go as far as saying they are purposely trying to mislead anyone. It comes down to uncontrollable variables and how the testing is done.
They sometimes use pressure barrels and take readings right at the muzzle. Both of which will give higher readings by themselves. Some are just calculations that are based upon pressure readings.

Ballistic calculations are great tools to implement but as Dallan has said if you must know the actual value...... shoot it on paper. I'll add, do it under the conditions you're gonna use the information for.

djwarner · Rookie Member Joined: Dec 23, 2009 Posts: 10

Went back to the manufacturers websites and found the correct BC's for both loads (.33 for the Hornady and .218 for the Federal). I was able to get balistics within 1% of the mfg's data woth the online PointBlank software.

Comparing the balistics charts for Hornady Leverevolution 160gr and Federal soft nose 150gr FN , I was at first confused be the similarity of the balistic arcs when using the same sights. Hornady touts that their boat tailed bullet greatly extends the range of the 30-30 load. From what I could tell, it would have about 2.84" less drop at 250 yds.

It turns out that the real significant difference between the two loads is that the Hornady slows less and retains more energy at extended ranges. +37% more energy at 200 yds and 48% more energy at 250 yds. In fact it has as much energy at 300 yds as the Federal had at 180 yds.