precision rifle match zero question.

[colbyjack]

Local club is having a precision rifle match coming up this spring. I have a 16" with a Eotech and flip up back up irons. The match will have plates and poppers from 100-300 yards. I'm zerod at 50. I'm assuming the 50/200 yard zero with +/- 1" from close to 100 and back on at 200. I need to chronno my load and actually try to see where its at at LNG distance. Problem is I have no where to practice over 100. So my practice is the match. If I assume the 50/200 hold is correct. How do I hold at 300 for a plates? Or should i try to zero my back up irons at 300 and use Eotech for others? Any help or ideas would be great. Thanks guys.

[CJW]

You need to chrono your ammo. You need to measure the height of your EOtech reticle above the centerline of your barrel. Then you go to JBM Ballistics (or your favorite smartphone ballistics app, like Strelok), punch the numbers in, and get a reasonably accurate profile of your bullet trajectory. Now, if you don't have a chrono and you are using the info written on the box of ammo, your 16" barrel is probably going to lose 100–200fps over the printed values.

Sight height is the single biggest factor for the ranges you are talking about. EOtechs tend to be kind of high; mine was right around 2.75" above bore. For 55gr M193 or 69gr MatchKings, I saw pretty similar profiles out to 300yds from my 20" barrel. With a 50yd zero, I was +/- 1" at 200yds and 8" low +/- 2" at 300yds. That works out to about 3MOA or 1MIL holdover at 300yds, but if you are really talking a precision match (targets of 1–2 MOA size) you'll need to do the detailed approach above. You'll also be about 1.5"–2" high around 150yds (highest deflection) and you'll be around 2" low at 25yds. These are ballpark numbers only, of course—if your precision match has you doing headshots through a soda straw at 25yds, you'll need to know more exactly.

While I wouldn't trust just a ballistics chart without actual verification shots for longer distances, if your zero is solid and your numbers are right, a calculated chart should be plenty good enough for 300yds and in.

Edited February 20, 2014 by CJW

[colbyjack]

Thanks for the info. I'll chronno my ammo and try to zero in best I can. And I'll run the app. Thanks. Very helpful!

Worst case I'll shoot my bolt gun for fun. I didn't think if the heavier bullets. All I got new is 55 grain. Didn't even think of running the 69. Was just trying to make what i had work. Hmmmmm well... Lol also this is out first match like this. So i think he said its all steel plates and poppers. I'll check to be sure. If I have to thread a needle. I may want a scope and the 69g...

[CJW]

Don't worry about the ammo at 300yards. The ballistics will be pretty close to the heavier bullets and, as long as the wind isn't much, you won't see a lot of drift difference. What you will see is that you're going to get 2MOA (maybe more) of spread in your pattern from the M193 than you would from match bullets. If your targets are 6" @ 200yds or 8" @ 300yds, you should be fine. Plenty of guys in 3-Gun are shooting M193 out past 300yds without much trouble. Golf balls at 200yds might be tricky, though.

[larry weeks]

CJW really covered it well so I'll add more that's already been said. I'm shooting an 18" with XM 193 and an EOTech, zeroed at 50/200, although zeroed at 50 it actually hits about 1" high at 200. I just hold at the top of a 10" MGM flasher at 300. That exactly matches what CJW said. As long as I don't jerk the trigger it hits. Just remember to aim a bit low in the 150 range, as CJW said. On skinny sammies at 125 I put the dot on the bottom of the round portion of the target.

[GM2B]

Zero at 200 then check it at 50. Not the other way around... Each click has 4x value at 200 so if your 50 yard zero is not 100% precise your 200 will be off. I have watched many many people miss plates at 200+ and say well I zero'd at 50 yards... Chrono if you want but knowing where it hits with your ammo is most important!

[mpeltier]

With a 200 zero my ballistic calculator shows a drop of 7" to 10" with loads from 2650 to 3000 fps. At 300. Hold accordingly based on the target size. Hope this helps.

Forgot to add that's for a 16" bbl with an eotech.

Edited February 23, 2014 by mpeltier