SIGforum.com    Main Page  Hop To Forum Categories  Mason's Rifle Room    AR15 zero
Page 1 2 
Go
New
Find
Notify
Tools
Reply
  
AR15 zero Login/Join 
Freethinker
Picture of sigfreund
posted Hide Post
quote:
Originally posted by RHINOWSO:
Good luck with that...


I merely changed the position of an Aimpoint sight on an AR rail, and it changed the point of impact at 50 yards by 4 inches.




6.4/93.6

“Wise men talk because they have something to say; fools, because they have to say something.”
— Plato
 
Posts: 47364 | Location: 10,150 Feet Above Sea Level in Colorado | Registered: April 04, 2002Reply With QuoteReport This Post
Member
posted Hide Post
quote:
Originally posted by RHINOWSO:
quote:
Originally posted by Sig209:
i like that you could place that 100yd zeroed Nikon on a .223 or .308 AR and - in an emergency - not have to re-zero it

Good luck with that...

Yes, they might have the same general trajectory if fired out of the same rifle with an identically installed barrel, but you have no idea if the zero between rifles is remotely the same.

Don't believe me? Take 5 AR15s, zero an optic on one, then move it to the other 4. You'll likely see impacts all over the place from rifle to rifle.

I have seen impact changes simply by moving an optic forward or back on the same rifle while getting eye relief spot on.


you know - you should really work on your tone-

you provide good relevant info in many of your posts but your verbiage is very condescending and rather asinine

you start off your response with sarcasm and later add the unnecessary challenge - 'don't believe me?'

seriously - take it for what it's worth - you really come across basically as a jerk which is unfortunate

it is a detriment to the info you can provide

note i said - in an emergency - not as standard practice

-----------------------------------------


Proverbs 27:17 - As iron sharpens iron, so one man sharpens another.
 
Posts: 8940 | Location: Florida | Registered: September 20, 2004Reply With QuoteReport This Post
Member
posted Hide Post
quote:
Originally posted by Sig209:
it is interesting how close .223 and .308 trajectories are at closer ranges (under 400yds for example)
basically the same for practical purposes

i like that you could place that 100yd zeroed Nikon on a .223 or .308 AR and - in an emergency - not have to re-zero it

From a drop standpoint, 223 (especially 73-77 grain) and 308 (especially 168-175 grain) are pretty similar out to 400 yards. Actually, most centerfire chambers with roughly similar muzzle velocity have reasonably close drop numbers out to 400 yards -- especially with a 200 yard zero.

Therefore, for mid-range engagements on reasonable-sized targets, the drop reticles for 223 and 308 are pretty darn close to being interchangeable.

Swapping optics from one rifle to another can be a crap shoot, however. During one of my optics upgrades a few years ago, I moved a scope from a 6.5 GA Precision bolt action to a 308 GA Precision rifle. I just loosened each base of the two rings on the 6.5, kept the scope in the upper part of the rings, and installed the setup in virtually the same place on the 308. Voila, the 308 with the new scope was really close to being zeroed at 100 yards.

I am again in optics upgrade mode. Last night I passed a scope that's mounted in Nightforce's one-piece from one Wilson Combat AR-15 to another Wilson. Using a dot on the wall about 10 yards away, performing a good look through the bore, I could see the crosshairs for the 2nd AR were noticeably down and right from where they were on the first AR. This means the alignment of the receiver's top rail to the bore is definitely different on the two virtually identical ARs. Noticeable at a distance of only 10 yards. It was getting late in the evening, so I decided not to futz with bore sighting. I think I will wait for the weekend then zero with live ammo on paper.

Bottom line -- it may not be the best idea to move an optic from one rifle to another, then expect the second setup to work as well as the first.
 
Posts: 7851 | Location: Colorado | Registered: January 26, 2008Reply With QuoteReport This Post
Still finding my way
Picture of Ryanp225
posted Hide Post
quote:
Originally posted by sigfreund:
quote:
Originally posted by RHINOWSO:
Good luck with that...


I merely changed the position of an Aimpoint sight on an AR rail, and it changed the point of impact at 50 yards by 4 inches.


I never thought it would have that drastic of an effect. Thanks for the info.
 
Posts: 10825 | Registered: January 04, 2009Reply With QuoteReport This Post
Member
posted Hide Post
I know others have good luck. BUT I have never had any success taking an optic off and putting back on the same gun in the same position and getting anything but serious POI changes. Sure its fine for 50m home defense, but longer not a chance. Putting it on a different gun also not a chance.


“So in war, the way is to avoid what is strong, and strike at what is weak.”
 
Posts: 10966 | Registered: October 14, 2004Reply With QuoteReport This Post
Armed and Gregarious
Picture of DMF
posted Hide Post
quote:
Originally posted by joatmonv:
https://youtu.be/jttB1kUXfJE

Thoughts? I did the 25 meter zero but I'm thinking this might be better.
Good info here.
I'll assume you are using a 5.56mm/.223, and unmagnified sights/optic.

If those assumptions are true I recommend a 50/200yd zero.

With most 5.56mm loads that will keep the bullet within 2" of the aiming point all the way out to about 225yards. While it's possible to score hits past 225 yards, most of us won't need to engage targets out that far, let alone beyond. Meaning for most situations engaging targets is "point and click."

Now, at work we train for making fast accurate shots, including possible hostage rescue shots. For that reason I prefer the EOTech circle/dot reticle.

With the 65MOA circle, when zeroing the dot for 50/200 yards, the round is within 2 inches of the dot all the way out to about 225 yards. But when a quick and precise short range shot (10 yards or less) where 2" of error is unacceptable, the bottom of the circle allows for quick and precise shooting.

It increases speed in those situations as there is no need to figure out where the dot needs to go to account for the mechanical offset. No worries about vertical or lateral error as the hash at the bottom of the circle IS the zero. We've tested this on a timer, and it's faster and more precise. A local agency has done the same with similar results.

Even when the precision is not needed, and +/- 2" is close enough, it's faster to find the dot when the eye is guided by the circle, or at "CQB" ranges just put the whole circle COM, and go with no need to focus on the tiny dot. Again, we've tested it, and it's faster to score hits.


___________________________________________
"He was never hindered by any dogma, except the Constitution." - Ty Ross speaking of his grandfather General Barry Goldwater

"War is the remedy that our enemies have chosen, and I say let us give them all they want." - William Tecumseh Sherman
 
Posts: 12591 | Location: Nomad | Registered: January 10, 2003Reply With QuoteReport This Post
fugitive from reality
Picture of SgtGold
posted Hide Post
quote:
Originally posted by sigfreund:
quote:
Originally posted by RHINOWSO:
Good luck with that...


I merely changed the position of an Aimpoint sight on an AR rail, and it changed the point of impact at 50 yards by 4 inches.


I made the mistake of thinking I could loosen the rings and slide an optic forward to adjust eye relief. Holy instant un-zeroed scope Batman!


_____________________________
'I'm pretty fly for a white guy'.

 
Posts: 7069 | Location: Newyorkistan | Registered: March 28, 2007Reply With QuoteReport This Post
Go ahead punk, make my day
posted Hide Post
Yeah moving optics can have all sorts of consequences - I consider a rifle in need of rezeroing if any changes are made to the optic / mount setup and wont use it until I can get it sighted in again.

The only 'rough' / 'emergency' zero I would place any faith in would be a RDS zeroed to a known good set of BUIS. Even then, there are differences, but IMO it would likely be good enough for HD hits out to 50yards.

When moving optic to a different rifle, there are many tolerances that can affect it. First is mounting location / spec. On an AR15 it is mounting to a picatinny rail section, however I see variances when adjusting QD mounts to milspec rails - nearly all of them have to be tightened or loosened to fit snug between individual rifles. Next is barrel installation. Is it perfectly aligned and torqued the same? What is the barrel length and muzzle device? Are they the same, different, etc?

This has all led to my habit pattern of doing optics changes the day before I go to the range, as I hate having essentially useless weapons in my safe.
 
Posts: 45798 | Registered: July 12, 2008Reply With QuoteReport This Post
fugitive from reality
Picture of SgtGold
posted Hide Post
quote:
Originally posted by RHINOWSO:
The only 'rough' / 'emergency' zero I would place any faith in would be a RDS zeroed to a known good set of BUIS. Even then, there are differences, but IMO it would likely be good enough for HD hits out to 50yards.


This has been my experiance as well.


_____________________________
'I'm pretty fly for a white guy'.

 
Posts: 7069 | Location: Newyorkistan | Registered: March 28, 2007Reply With QuoteReport This Post
Member
Picture of jezsuiz
posted Hide Post
I do 100yds on everything AR related. I have been told this is the best range.
 
Posts: 556 | Location: NE not new england | Registered: October 15, 2008Reply With QuoteReport This Post
Member
posted Hide Post
When you mount any optic on a rail, push the mount forward with slight pressure while you tighten it. This way when you take it off, remount it in the same fashion it should be in the same place. There is always a little slop between the rail and the mount, by doing this it should mount the same (or close to it). Also when the rifle is fired, the recoil pushes back on the mount, it the mount is all the way forward there is no room for movement, should the mount loosen at all.
 
Posts: 1913 | Location: U.P. of michigan | Registered: March 02, 2010Reply With QuoteReport This Post
Member
posted Hide Post
quote:
Originally posted by jezsuiz:
I have been told this is the best range.

It may be the best zero distance for the person who told you that. It may be the best zero distance for you, or it may not be the best zero distance for you.

You should understand the flight ballistics of the various zero distances, consider your expected shooting distances, consider the type of shooting you do, and consider your desire for elevation holding and/or dialing.
 
Posts: 7851 | Location: Colorado | Registered: January 26, 2008Reply With QuoteReport This Post
Fighting the good fight
Picture of RogueJSK
posted Hide Post
With unmagnified optics, my preference is for a 100 yard zero (I would have no issue using a 50 yard zero either, but wouldn't want a 25 yard zero.)

With a 100 yard zero, I like that the bullet never rises above the line of sight. So you don't have to worry about holding over at certain ranges, and then holding under at other ranges, when trying to be precise. It's all holdover with a 100 yard zero.

And at 0-200 yards, the bullet will impact at most an inch or two below your aiming point anyway, which is good enough for rough target engagement without worrying about holding that inch or two over, when speed is needed.

The tradeoff is that it drops more sharply after 200 yards than a 50 yard zero, but I don't plan on shooting much past 200 yards with unmagnified optics anyway.

 
Posts: 32417 | Location: Northwest Arkansas | Registered: January 06, 2008Reply With QuoteReport This Post
  Powered by Social Strata Page 1 2  
 

SIGforum.com    Main Page  Hop To Forum Categories  Mason's Rifle Room    AR15 zero

© SIGforum 2024