Range Report Help on Fed .308 bthp trjectory

[Toebuster]

Can any one confirm my data on .308 168gr Fed BTHP Match ammo out of 24 inch barrel at 2650 fps?

On my data, I'm getting 42.6 inch drop at 500yds with a 200yds zero using G7 BC.

However, on Federal's website they list a 51.5 inch drop at 500yds with the same 200yds zero as well as the same MV at 2650.

What am I doing/reading wrong?

Thanks.

 

[DirtyRod]

Re: Help on Fed .308 bthp trjectory

The ballistic data posted is test data from some other random gun. Most likely one with a barrel shorter than 24 inches. Even so, no two rifles will shoot the same load exactly the same so consider whatever posted data you see as a guide. If 42.6 is what you get then that's the dope for your gun.

 

[gstaylorg]

Re: Help on Fed .308 bthp trjectory

Seems like you'd need to be going a lot faster than 2650 to get that drop at 500 yds with FGMM 168s. How sure are you about the MV and actual range you're shooting?

 

[DirtyRod]

Re: Help on Fed .308 bthp trjectory

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gstaylorg</div><div class="ubbcode-body">Seems like you'd need to be going a lot faster than 2650 to get that drop at 500 yds with FGMM 168s. </div></div>

I was thinking the same thing. I was dialing 10.5 MOA for BH 168s out of a 26" barrel @ 2656 which should be a drop of 54.96" if my calcs are right.

 

[Toebuster]

Re: Help on Fed .308 bthp trjectory

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dirty Rod</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gstaylorg</div><div class="ubbcode-body">Seems like you'd need to be going a lot faster than 2650 to get that drop at 500 yds with FGMM 168s. </div></div>

I was thinking the same thing. I was dialing 10.5 MOA for BH 168s out of a 26" barrel @ 2656 which should be a drop of 54.96" if my calcs are right. </div></div>

The 42.6 inch drop I got from the Shooter app. I double checked that all the info I input is correct but it's still off by 10 inches at 500yds. Can't figure out why.

 

[gstaylorg]

Re: Help on Fed .308 bthp trjectory

If I'm understanding you correctly, it's the app that is giving you a <span style="font-style: italic">predicted</span> drop of 42.6" at 500 yd? If so, it is likely that at least one of your inputs was off. Something to do with input, anyhow. I would suggest you (re)check your atmospheric inputs, scope height above bore, etc.

Also, have you actually shot that ammo and determined your <span style="font-style: italic">true</span> drop at that distance? Or were you simply trying to generate a drop chart prior to shooting it at the range? Reason I ask is that under a fairly general set of conditions (70F, 29.95" Hg, 60% humidity, 1000 ft altitude, 200 yd zero, 2" scope height), JBM ballistics predicts you'd need an MV in the neighborhood of 2875 fps to get a 42.6" drop @ 500 yd. Using 2650 fps (all other conditions held the same), JBM predicts 51.3" drop @ 500 yd, which is very close to that predicted by Federal.

So have you actually shot some yet? If so, what was your actual drop? If you're trying to generate a drop table before shooting it, I'm thinking it almost has to be an input error, although it's difficult to say what it might be without knowing all of your input parameters. In any case, if you figure it out, let us know.

 

[Ultraman550]

Re: Help on Fed .308 bthp trjectory

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Toebuster</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dirty Rod</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gstaylorg</div><div class="ubbcode-body">Seems like you'd need to be going a lot faster than 2650 to get that drop at 500 yds with FGMM 168s. </div></div>

I was thinking the same thing. I was dialing 10.5 MOA for BH 168s out of a 26" barrel @ 2656 which should be a drop of 54.96" if my calcs are right. </div></div>

The 42.6 inch drop I got from the Shooter app. I double checked that all the info I input is correct but it's still off by 10 inches at 500yds. Can't figure out why.



</div></div>
For what its worth Shooter and Ballistic FTE are an average of 1-1.5 MOA off compared to what I actually get in elevation. 100 yards to 200 yards its pretty accurate but starting at 300 yards is when I get the variation. I just dial in 1 MOA less and it works perfectly. I haven't done it yet but in the Shooter app when you input everything and then press calculate is brings you to the settings. At the top there is a tab for "solution I table I graph". To the right is another button with an arrow in a box pointed to the right. When you press that button it brings up a choice of "show lead I Email table I Velocity calibration". You can enter in your own data here up to 4 distances and it should recalibrate everything which should make the application results match up more evenly to what you actually get shooting.

 

[Toebuster]

Re: Help on Fed .308 bthp trjectory

Yup, it's the app that's not adding up for me.

I've been invited by my friend for a day of shooting on his property, that has a good line of sight to a little more than 500 yds. So basically, I'm trying to get all my numbers down in advance.

I'll try your suggestions and double/triple check my inputs again.

Thanks fellas.

 

[gstaylorg]

Re: Help on Fed .308 bthp trjectory

If the range trip is coming soon and you haven't been able to figure out the Shooter app to your satisfaction, just plug your #s into JBM. It works very well. Have fun at your shoot!

http://www.jbmballistics.com/cgi-bin/jbmtraj_simp-5.1.cgi

 

[Unknown]

Re: Help on Fed .308 bthp trjectory

I had the same sort of thing come up when shooting my 300 Win mag at a 1000 yard range. I figured the dope according to my chronograph, and when I got to the range there was about 5 MOA less drop. It turned out that there was a very slight uphill angle to the 1000 yard target butts.

I tracked backwards what my velocity for a 190 Sierra BTHP would have to be to make such a difference. My chrono showed 2960 FPS, and velocity for the drop I got would have had to be somewhere around 3200 FPS for a 190 grain bullet. There is no way I would deliberately shoot ammo that hot in my rifle.

The loads were out of the same lot that I chrono'ed, and temperature was a cool 60 degrees Fahrenheit with a light drizzle of mist...not quite to rain drizzle yet. So I know temperature hadn't raised the velocity..

When I figured in the angle, everything worked out.

 

[Toebuster]

Re: Help on Fed .308 bthp trjectory

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: gstaylorg</div><div class="ubbcode-body">If the range trip is coming soon and you haven't been able to figure out the Shooter app to your satisfaction, just plug your #s into JBM. It works very well. Have fun at your shoot!

http://www.jbmballistics.com/cgi-bin/jbmtraj_simp-5.1.cgi </div></div>

Perfect. Thanks!