AR15.Com Archives
 Help with minimal range .308 sight in
HEADHUNTER1976  [Member]
5/23/2010 10:16:21 AM
I have very little time to get to any gun ranges due to my work schedule, the closest is an hour away and is only available to civilians on Saturdays from 1- 5 pm. I do however have a good back stop that I can shoot into and have a little bench set up at 25 yards (the max I can get to is about 40 yards then I run out of room due to a steep drop off). I have an Armalite AR10 A4 with a Pride-Fowler RR800-1 "Rapid Reticle" Scope designed for .308 BDC out to 800 yards (as long as you know your range, for this in actual use I plan on getting a good range finder). The problem is I (being a novice at best) do not know what I need to dial the scope in for at 25 yards to get me as close as possible when I finally do get to shoot at 100 yards plus to verify zero. If anyone knows where I need to have this rifle placing rounds at 25 yards to achieve this then please let me know. BTW I mostly shoot quality surplus like Hirt., Port, etc. but have some 150 gr. sp ammo for deer hunting. All I really need from this rifle is to be capable of placing a kill shot at the stated ranges on the reticule, not 1-2 MOA, just placed well enough to kill a deer sized target. Thanks for any help and God bless.
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jimhoff  [Team Member]
5/23/2010 1:46:03 PM
My DPMS AP4 was 3" low at 300 yards from what the balistic chart said it would be. What is the height of the scope? What ammo?
Gamma762  [Team Member]
5/24/2010 2:59:38 PM
At 25 yards you'll need to correctly compensate for the height over bore of the sighting system you are using, in order to get something reasonably close in elevation at longer ranges.
jeep45238  [Team Member]
6/1/2010 6:34:31 AM
A M1A zero'd at 25 meters will hit POA/POI at 250 meters. That should get you relatively close.
Scottv  [Member]
6/11/2010 6:26:56 PM
You really need a ballistic calculator that will let you enter the scope offset into the equation. There is a free one at www.biggameinfo.com that seems towork fairly well.
The more of the excat info you can enter in the table the better the results. there will be varibles but it should save you time and money when you get to the range.
Scott
www.centerfiretraining.com
rarelyaccurate  [Member]
6/22/2010 9:56:00 PM

Take the upper off your AR10 remove the bcg, mount it on a table/sandbag. Look down the bore find something to look at, prop your upper in such a way that it won't move. Adjust the reticle on your scope so it matches up with exactly what you see when looking through the bore/barrel of your rifle.

it depends on your rounds but I would try to set your zero at 25, so that you are aiming dead center and you're bullet hits 1.5" low. that will get you close to zero at 100, from there shoot and adjust.

Heck you could even skip the shooting rounds at 25 step, and just eyeball bore sight it roughly 1.5" low. So you would aim the reticle dead center at the target, but the bore/barrel should be aimed 1.5" low of that. And just start shooting at 100 yards from there, it won't be exact but you'll be close enough to adjust.
RugRat  [Member]
7/1/2010 11:40:38 PM
I'm not bragging, just informing.

By looking down the bore and matching the reticle to the object in the center of the barrel, we get on paper at 200 meters every time.

That takes all the sight height issues out of the equation and gets you zeroed at 200 meters with about five shots.

You gotta go slow and look carefully down the barrel to do this, but it works every time.
CHUCK6419  [Member]
7/7/2010 2:29:23 AM
I've shot several rifles at 25yards at an indoor range I used to work at... The general rule was... 1"-2.5" low at 25 yards would put it right at about 100 yards. Dead on at 25 yards was good at 200. this was just about right for any bullets going 2700 to 3000 fps. BUT you have to MAKE the Time to go shoot it at said distances... otherwise you are just guestimating, yes youll probably keep on a deer at 200 yards but farther than that you will have to know what your rifle does!

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