Range Report Ballistic FTE

[bosulli]

Still figuring out the Iphone Ballistic FTE app.

I was at the range today. Wanted to document the dope on an AR 223, surplus 55gr ammo, Eotech 552. Its zero'd at 25yds. It shot 1.5" low at 10 yds. At 100yds it was 8" high.

Tried to plug in variables into my Ballistic FTE app, and never could reproduce those results. I believe sight height is the significant variable.

Anyone know why I could not reproduce the empirical trajectory on the Ballistic FTE app?

 

[Lindy]

Re: Ballistic FTE

A zero at 25 yards is a zero designed for maximum point-blank range with that cartridge, so that combat shooters can hold center mass on threats between muzzle distance and 300 yards, and be assured of hitting the threat in a good place.

A 25 yards, the bullet trajectory is <span style="font-style: italic">rising</span>, and will reach maximum ordinate somewhere in the vicinity of 200 yards, descending to cross the line of sight again around 300 yards.

So, of course the bullet will be high at 100 yards.

You might want to experiement on JBM, where you have a screen with more room.

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

Pretty much no one else uses that kind of zero.

 

[bosulli]

Re: Ballistic FTE

That JBM site is a great tool!

The actual trajectory did not surprise me, mastering the Ballistic FTE app is the challenge.

I am tinkering with a new EoTech optic. Although I had it zero'd at 100yds, I wanted to try a 25yd zero for an upcoming 3 gun shoot, that will have a few long range targets. Not that I am relying on the Ballistic FTE app to calculate trajectory in the field for an optic zeroed at 25yds, just seeing if I could figure out how to make the app replicate it.

BTW, I purchased the EoTech 552 on the advice of someone whose location on another site was "On the beach, Rockport, TX" . Coincidence?

 

[Lindy]

Re: Ballistic FTE

Yeah, probably just a coincidence - Rockport is a hotbed of shooters...

There are two gun stores in town, neither of which has a single thing I'd contemplate owning.

Personally, I zero my carbine at 100 yards, and then just hold over relative to the size of the target beyond that. But I know other guys who zero at 50 yards, so there's certainly more than one way to skin that cat.