55gr AE223 ballistics

[Onagoth]

Hoping you guys can help.

I know I have to chrony this ammo to get the real answer, but in the meantime, maybe you guys have some opinions.

I buy this ammo in bulk 1000 cans, and it is supposed to be 3250 fps with a BC of 0.265, from what I have read.

When I plug this into my android app, Strelok, the POI of this cartridge is supposed to match the reticle (almost exactly) on my XTR scope.

Well, I tested it out yesterday at 300y, and I had to use the 400y bullet drop indicator on the scope to get hits....Which is a significant difference. I plugged all the specs above into Strelok to get the POI, but it wasn't close.

This leads me to believe either 1) the ballistic app sucks, or 2) the ballistic information I have on this cartridge is grossly misstated.

For what its worth, I pplayed around in the ballstic app to get the POI to be the 400y hash mark on the scope (where the actual hits are). To get that, the muzzle velocity had to be around 2700 fps or the BC had to be around 0.15. Both cases seem highly unlikely.

Any thoughts?

Edited April 24, 2012 by Onagoth

[SteveT-NV]

Hoping you guys can help.

I know I have to chrony this ammo to get the real answer, but in the meantime, maybe you guys have some opinions.

I buy this ammo in bulk 1000 cans, and it is supposed to be 3250 fps with a BC of 0.265, from what I have read.

When I plug this into my android app, Strelok, the POI of this cartridge is supposed to match the reticle (almost exactly) on my XTR scope.

Well, I tested it out yesterday at 300y, and I had to use the 400y bullet drop indicator on the scope to get hits....Which is a significant difference. I plugged all the specs above into Strelok to get the POI, but it wasn't close.

This leads me to believe either 1) the ballistic app sucks, or 2) the ballistic information I have on this cartridge is grossly misstated.

For what its worth, I pplayed around in the ballstic app to get the POI to be the 400y hash mark on the scope (where the actual hits are). To get that, the muzzle velocity had to be around 2700 fps or the BC had to be around 0.15. Both cases seem highly unlikely.

Any thoughts?

Not sure if this will help or not but, before I started reloading I was shooting the AE 55 grain FMJ and was getting an average MV of 2905 fps out of an 18 in JP SCR11. As you said you would have to chrony your rifle to see what you are getting.

FWIW, I also use the Strelok calculator and I have found it to be pretty accurate, and it correlates pretty close to other ballistic calculators like the one at JBM Ballistics

From my previous reading I don't think that it is that uncommon for the ballistic reticles to not correlate that well with actual results, especially with factory ammo. Ideally you would make up a custom load to work with your reticle.

Before giving up though, it may be worth double checking your rifles zero, making sure you are getting reasonable groups at distance, and measuring the drop in your groups at set distances to see what you are getting. But, you really need to know your MV to check your ballistics.

Steve

[Onagoth]

Thanks for the help Steve.

It would be really helpful if someone knew the BC of this ammo as well. I think the best I found was a post in a forum from someone who said was it is, but I couldn't find it on Federal's website.

[SteveT-NV]

Thanks for the help Steve.

It would be really helpful if someone knew the BC of this ammo as well. I think the best I found was a post in a forum from someone who said was it is, but I couldn't find it on Federal's website.

The downloadable Fed Prem Catalog has the BC at 0.269

Steve

[Onagoth]

Perfect! Thanks again.

[Onagoth]

FWIW, I really don't know why it could be off. The app is supposed to give me a POA on the reticle that my scope uses, given the load data that was input. I'm at a loss for why this is happening and I doubt muzzle velocity is the answer.

The only other thing can I think of is that I wasn't shooting at 4x, which the reticle output from the app is based on.

[BC98]

FWIW, I really don't know why it could be off. The app is supposed to give me a POA on the reticle that my scope uses, given the load data that was input. I'm at a loss for why this is happening and I doubt muzzle velocity is the answer.

The only other thing can I think of is that I wasn't shooting at 4x, which the reticle output from the app is based on.

Onagoth,

I know the topic is a little bit older and I'm not sure if you got the answer that you were looking for but the answer to your POI difference is most likely a difference in muzzle velocity. The MV listed on the box of ammo is typically data from a 24" test barrel (per SAAMI spec) unless otherwise noted. The poster who had the 18" chrono data at around 2900 fps sounds accurate. I typically use an estimate of 50fps velocity loss per inch of barrel length on .223 and it has held up.

If you're shooting the ammo out of a 16" barrel (I didn't see if you had mentioned it), the the velocity that you calculated for your POI is probably pretty close to what you're getting out that barrel.

[bgary]

FWIW, I really don't know why it could be off. The app is supposed to give me a POA on the reticle that my scope uses, given the load data that was input. I'm at a loss for why this is happening and I doubt muzzle velocity is the answer.

I'd almost guarantee that the muzzle velocity is the answer.

To begin with, your barrel is almost certainly shorter than the test fixture they used, when they chrono'd it. If they did. But more than that, almost all manufacturers are...uh..."optimistic" with their published MV numbers, in much the same way that car manufacturers...uh..."help" their mpg numbers. It's just the nature of the beast.

What really matters is what the rounds do thru your barrel. If you shoot at 100, 200, 300, 400 and log your actual bullet-drops, you should be able to model the trajectory in your ballistic program and figure out what the MV has to be to be producing those results. I don't know about the Federal ammo, but a lot of 55gr ammo uses the Hornady FMJ which, IIRC, has a BC of .243.

Two other things: One, make sure that your ballistic program is using the right drag model. A BC of .243 (or whatever) using the G1 model is going to produce a very different trajectory than the same BC figure through the G7 drag model. And two, note that BDC reticles are really only ever "on" if your round (MV, BC, sight-height) *exactly* matches the trajectory the reticle was designed for. If there are any differences, your 400-yard stadia (for example) is *not* going to be "on" at 400 yards. With many BDCs it makes more sense to work backwards - shoot at distances, log the drops, then figure out what the various stadia "mean" for your ammo. It may well be that the 300-yard stadia is "on" at 275 yards, the 400-yard stadia is "on" at 360 yards, etc. That's not a bad thing, it just means you know where it hits based on real data rather than ammo-box labeling.

$.02

[Nuke8401]

The only other thing can I think of is that I wasn't shooting at 4x, which the reticle output from the app is based on.

I was going to ask that very question on your other thread but thought, he knows that.

So yes, the only time the reticle will work is at the designed power (second focal plane), which is I think 4X on the XTR.

I shoot a 16" and count on 300 - 400 FPS loss from manufacturer data, so 2800 FPS is not out of the question.

One last bit of advice, use the 200 yard mark and zero at 200, your 100 will be close enough and your 300, 400 will be beter. Also run the calculator with a 200 zero and see if that improves your 300, 400 marks.

David E.

[BrianATL]

FWIW, I really don't know why it could be off. The app is supposed to give me a POA on the reticle that my scope uses, given the load data that was input. I'm at a loss for why this is happening and I doubt muzzle velocity is the answer.

The only other thing can I think of is that I wasn't shooting at 4x, which the reticle output from the app is based on.

Uh I believe your Burris is a second focal plane scope which means your BDC is calibrated only for one particular power generally the highest power of the scope.

[Onagoth]

Thanks guys,

I've since figured out a large portion of the variance. Of course, the muzzle velocity was less than published, which I knew already. it was roughly 2900 ft/sec as another member stated

What I underestimated was the load data that went into the calibration of the drop marks on the XTR scope. For one, it was based on the following:

62 gr bullet pushing 3025 ft/sec with a BC of .307. Sight height of 2.3"

My load was the following:

55 gr bullet pushing 2900 ft/sex with a BC of 0.269. Sight height of 2.75"

Metric vs imperial distancing also accounted for some of the change, I was actually shooting at 300m which is roughly 330y. I knew this but underestimated the effect. I completely forgot about the effect on the zeroing distance 100m is 110y.

Overall, I figured out a large portion of the difference by isolating one factor at a time. These factors explain about 2/3 of the actual results I am seeing. Ie, at 330y, my load should have a POA of almost 2/3 between 300y and 400y marks, but it is pretty much exactly on the 400y drop marker in reality.

I think the remaining difference might be a less than advertised BC on my factory ammo and sight height variances (I didn't measure it exactly).

I've pretty much given up on it and will see what happens with my long range load that I will be working on over the next month or two. I plan on just marking my POAs on a chart and noting them when taking shots at a long distance.

Edited May 7, 2012 by Onagoth

[Onagoth]

Since I will be marking my bullet drops, it kind of defeats the purpose of why I bought a BDC reticle. unless it holds up well for my heavier 68/69gr long range loads, I am also considering switching to an MOA or MRAD reticle.

I kind of liked the Vortex PST 1-4x with MRAD.