Question on Ballistics Drop for Vortex Spitfire 5.56 Reticle

[UP2MTNS]

Hey all,
Recently got a Vortex Spitfire 3X and had a question on the retical. I'm new to shooting anything over 100yards so was doing a little research and wanted some others' opinions.


So the basics of the Spitfire 5.56 reticle is you're supposed to zero the top crosshairs at 100yards and that acts as your 100/200yr holdover and then it goes out to 500 yards (see Pic 1 below). They do tell you when shooting to 200yards to hold the crosshair 1.5MOA high to account for it, so...whatever.

Now, looking at the reticle measurements in MOA.....500 yards is 12.5 MOA from that initial cross hair (see pic 2 below).


BUT, using a BASIC online ballistics calculator, it looks like with a 200yard zero, a 12.5 MOA rise is more in line with 600 yards (see pic 3 below).


Is that right? I realize there's a ton of assumptions, yadda, yadda, yadda, but is that basically correct?

[FLIGHT762]

The most obvious mistake I see in your ballistic chart under "Variables" is you sight height listed as 1.5". That would not be correct on an AR platform, your sight height is actually 2.5"-2.75" depending the type of mount.

Change the sight height to 2.5" and see if you're any closer in the trajectory.

[Jimmy's]

All loads are not equal you will have to test this for yourself and find a happy medium. I have a few of these reticles and they work as intended. In theory your 200 yard sight in will work but not always give you the 600 this will vary with cartridge and it's capability.

[missiondude]

If your scope is second focal plane, you can find a magnification that will match your BDC to the actual performance of many different bullets. I have a Leupold with a varmint reticle that will do drop compensation for 55 gr up to 77 gr 223 ammo depending on magnification used, and it will be within 1 moa for all those different rounds. This would not apply to a fixed power scope.

[dwalker]

If your scope is second focal plane, you can find a magnification that will match your BDC to the actual performance of many different bullets. I have a Leupold with a varmint reticle that will do drop compensation for 55 gr up to 77 gr 223 ammo depending on magnification used, and it will be within 1 moa for all those different rounds. This would not apply to a fixed power scope.

A Spitfire is a 1X optic, not a scope. This is also why a FFP scope is better than a SFP scope, as the reticle and thus the holds stay the same throughout the magnification range.

[dwalker]

2790 is very slow for a 55gr bullet. 3240fps is closer to what you would see from a 55gr match bullet. ETA your also using a 200 rather 100yd zero. that is an important detail.

With a 100 yard zero and a 55gr HP-M projectile at 3040fps, the hold over is about 15.38, the hold at 500 would be 10.52inches, and this is why it is important to chrono ammo and be accurate in your ballistics. Its also why I dial and try to minimize holdovers, and why folks using holdovers but have not chrono'ed ammo and matched to thier BDC dump mags at long range targets in a mtach.

[UP2MTNS]

Sorry I wasn't clear...this is their 3x fixed prism scope.

The most obvious mistake I see in your ballistic chart under "Variables" is you sight height listed as 1.5". That would not be correct on an AR platform, your sight height is actually 2.5"-2.75" depending the type of mount.

Change the sight height to 2.5" and see if you're any closer in the trajectory.

you're right, thx for catching that. I wasn't paying attention and measured off the top of the rail, not from the barrel. 2.75"

2790 is very slow for a 55gr bullet. 3240fps is closer to what you would see from a 55gr match bullet. ETA your also using a 200 rather 100yd zero. that is an important detail.

With a 100 yard zero and a 55gr HP-M projectile at 3040fps, the hold over is about 15.38, the hold at 500 would be 10.52inches, and this is why it is important to chrono ammo and be accurate in your ballistics. Its also why I dial and try to minimize holdovers, and why folks using holdovers but have not chrono'ed ammo and matched to thier BDC dump mags at long range targets in a match.

I used a lower number because this is out of a 16" barrel, I'm not going to have the same velocity as what's on the box, but I just did some more quick searching and it seems like 2900fps is a better estimate. But yes, I need to just pick a few different ammo, chrono them and pick the best one.


Oh, and I noticed the 'ballistics coefficient' is way too high, so changed that along with the other fixes and found something that is pretty close to their measurements....so at least I have a good baseline.

This is with the zero at 100....500 yards is a little off, but this isn't supposed to be perfect at this point. Thanks for the feedback.

[FLIGHT762]

Just for the fun of it, try a 50 yard zero and see what that does. I do know this, we sighted are M4's with a 50 yard zero which gave us dead on @ 50 and dead on again @ 200 yards. See if that falls any closer with the BDC hold overs.

[dwalker]

Just for the fun of it, try a 50 yard zero and see what that does. I do know this, we sighted are M4's with a 50 yard zero which gave us dead on @ 50 and dead on again @ 200 yards. See if that falls any closer with the BDC hold overs.

If the optic calls for a 100yd zero then thats what you should use if you want the holds to work. My Burris calls for a 100yd zero, the Vortex Strikefire 1-6 I just picked up for my backup rifle calls for a 50/200 zero.

[UP2MTNS]

If the optic calls for a 100yd zero then thats what you should use if you want the holds to work. My Burris calls for a 100yd zero, the Vortex Strikefire 1-6 I just picked up for my backup rifle calls for a 50/200 zero.

yeah, but I think FLIGHT762 already sees what I'm trying to do....If I can zero at 200 and get 'close enough' and I just have to memorize the little holdover differences on the three other cross hairs, I could have a nice 600yard reticle. But its looking like I may have to zero at 300 yards to be able to do that.

Also, for distances over 300yards I'll be shooting the 75 or 77 grain stuff anyway, so what I'm really trying to do is merge the two (55gr vs 77gr) and see if I can have a true one-stop-shop.

It'll be a fun little experiment regardless.

[UP2MTNS]

ahhhh, this is what I'm talking about....so Don, that Hornady Steel Match ammo I was asking you about?....I entered in the specs for that ammo with a 300 yard zero and got this:



so, I'll have to chrono it to see if the fps is accurate, but if it is...this means at 300 yards I'm at the first cross hair with 75 grain. The next drop (4.4moa) is just a little low for the 3.6 at 400yards.

500 yard (8moa) should be dead on at 7.9

and 600 (12.5moa) is pretty damned close to 12.9.

[dwalker]

I like Steel Match, when you can find it. It has been very consistent ammo for me.

[nate76239]

If you zero at 300 based on the last ballistics then you're just swapping places with the 100 and 300 yard marks, 400 would be somewhere in between. I've used the Hornady 75 grain .223 match at 300 and 600 yards and the calculations are right on, my difference was around 3.7-3.9 mils with 18 and 20 inch barrels going from 300 to 600 yard zero.