Sport II question - is this spring from the rifle??

[Rastoff]

I don't have access to a printer at the moment but I will follow the same theory and measure the deviation from center to make necessary adjustments.

OK, that will work. All you need to remember is how much movement each click on your sights moves the group.

Since you have a Sport II, the front post is used for elevation and the rear is used for windage. Both are 1/2MOA per click. At 50 yards this means each click is 1/4". So, 2" move will require 8 clicks.

 

[ChattanoogaPhil]

OK, that will work. All you need to remember is how much movement each click on your sights moves the group.

Since you have a Sport II, the front post is used for elevation and the rear is used for windage. Both are 1/2MOA per click. At 50 yards this means each click is 1/4". So, 2" move will require 8 clicks.

I believe Magpul lists MBUS rear sight windage adjustment as .7moa for a 14.5in sight radius. IIRC an A2 front sight elevation adjustment is about 1.75moa per click (quarter turn) for the front sight post. Is the Sport different than this?

http://www.usaac.army.mil/amu/assets/zeroing.pdf front sight pgs 18-24

 

[rgkitchen]

I recommend this target to help remind you which way to adjust the front and rear sight... you don't have to shoot at this target, but keep it as a reference with you to make sure you are moving those sights the right way.

http://www.bobdbob.com/~deneb/doc/targets/m4-carbine-zero.pdf

Here is a revised 25 yard target in case you use a scardy cat state run range that doesn't allow any "man shaped" silhouettes, like Michigan.

http://www.bobdbob.com/~deneb/doc/targets/m4-carbine-zero-no-sil.pdf

 

[shep854]

What I have used more than once is a sheet of paper with a black dot inked at the center--the important thing is to get the range right, depending on your method of zero.
Shoot, adjust, shoot again. Repeat as needed.
Don't forget to also work on consistency with your sight picture, breathing and trigger press.

 

[Rastoff]

I believe Magpul lists MBUS rear sight windage adjustment as .7moa for a 14.5in sight radius. IIRC an A2 front sight elevation adjustment is about 1.75moa per click (quarter turn) for the front sight post. Is the Sport different than this?

http://www.usaac.army.mil/amu/assets/zeroing.pdf front sight pgs 18-24

This link didn't work for me.

You are correct about the .7MOA for 14.5" sight radius which is what the Sport II has. I could have sworn it was 1/2MOA for the front sight, but now I'm not so sure. I didn't think it was that coarse though. I did some research on the internet and there's a few different thoughts on that. I've found 1.5MOA and 2MOA and even some odd numbers. There's nothing in the M&P15 manual on it except how to move it.

 

[scooter123]

To me that looks like a Detent Spring for the takedown or pivot pins. if you removed the buffer tube for some reason you will find that the rear takedown pins doesn't have a detent in the open or closed position. because that particular spring is retained by the plate that holds the buffer tube to the receiver. As for the forward pivot pin, it is borderline impossible to remove that pin so it is highly unlikely this is the spring for the pivot pin detent.

 

[Rastoff]

To me that looks like a Detent Spring for the takedown or pivot pins.

No, those springs are long. This one is only 5mm.

 

[ChattanoogaPhil]

This link didn't work for me.

You are correct about the .7MOA for 14.5" sight radius which is what the Sport II has. I could have sworn it was 1/2MOA for the front sight, but now I'm not so sure. I didn't think it was that coarse though. I did some research on the internet and there's a few different thoughts on that. I've found 1.5MOA and 2MOA and even some odd numbers. There's nothing in the M&P15 manual on it except how to move it.

Here's a couple clips from it.

 

[DWalt]

One thing I would recommend is to shoot a close-in target first, say 15-20 yards. It's a lot easier to zero to make sure your sights are adjusted approximately correctly, then move back and re-zero at a longer distance, 50-100 yards. Typically a 25-yard zero will also be approximately correct at 100 yards. Unless you know you will be shooting at distances much greater than 100 yards, I always recommend a 100 yard zero as the best default setting.

 

[ChattanoogaPhil]

Typically a 25-yard zero will also be approximately correct at 100 yards..

That might be correct for something like a Marlin 30-30 with low profile iron sights. However, an AR platform has a very high sight over bore of about 2.5in. This makes zeroing at a close distance of 25 yards a great divergence of bullet path versus line of sight beyond 25yds and doesn't come back to zero again until around 400yds.

This graph displays a 25yd zero for an AR platform with sight over bore of 2.5 inches using a typical 55gr round. At 100yds the bullet strikes 6 inches high, 200yds 10 inches high, 300yds 9 inches high, and doesn't approach the line of sight again until close to 400yds.

 

[ChattanoogaPhil]

For those who are new to an AR platform and aren't quite sure about line of sight, bullet trajectory and zero, I would suggest using this ballistics calculator until you are familiar with the basics.

Select Bullet caliber (.223 Remington). Select Bullet Name

Then click "Advanced Options"

Manually enter Zero Range and Sight over Bore of 2.5in. Then manually enter Distance to Show (that's total yards to show on the graph) and Distance Step (each distance to get a measure of bullet drop). Click the Enter button.

Doing so will eventually take the mystery and myth out what zero will best serve your needs. Ballistic Calculator GunData.org

 

[uncledoggle]

Two things:

1. Did anyone ever answer the question in the OP?

2. Here's another prospective for sighting in your AR.
[ame="https://www.youtube.com/watch?v=jL5Oz4M5NVs"]https://www.youtube.com/watch?v=jL5Oz4M5NVs[/ame]

 

[ChattanoogaPhil]

Video is a good exercise in simply plotting the results of a ballistics calculator such as the example earlier in the thread. Nice illustration.

 

[shep854]

What the graph ChattanoogaPhil posts illustrated is what the military calls 'Battlesight Zero' (BZO), or the setting which should cause a shot to hit a human-sized target at 'normal' combat ranges without holdover or sight adjustment.
As the graph shows, a 25 yard zero allows this, and has the benefit of allowing useful live-fire training at reduced ranges.

 

[ChattanoogaPhil]

This is another illustration for 25, 50 and 100 yard zero to help determine what might best fit your needs.

For me, I live in the heavy woods of Tennessee and use a 1x red for center mass fast target acquisition and fire. No fuss no precision... simply point and click. Using the 50yd zero keeps the bullet path right in my line of sight staying within 2 inches above or below out to about 200yds or so. This works for the terrain, optic, and what I expect from my rifle.

If I lived in the desert I wouldn't be using a red dot but rather a magnified scope with BDC that has a manufacture required zero to match the reticle.

There is no perfect zero for all. Only what best fits your needs.

 

[ChattanoogaPhil]

There might be some newbies out there not quite sure about line of sight, trajectory and zero. Here's a good illustration of the most basic fundamentals.

 

[Cantthink0f0ne]

Hey dudes, couple of quick updates.

1) The rifle works, so that tiny spring is pretty much confirmed as not being from the gun.

2) I was definitely under-educated on sight zeroing, and after the extremely helpful posts here I would like to think that I am better informed.

While I did get a chance to fire it this past weekend, I didn't really have the chance or the right gear to zero in my sights properly. I forgot my rifle rest, and was backyard shooting so didn't have any way to conform the 50 yard target distance. With all that said, the iron sights seemed to put the bullet pretty damn close to where I was aiming so the factory zero was good enough to have some fun.

Next trip to the range I'll actually take my time to do a proper 50 yard zero, I think that's the most practical option for me at the moment.

Sent from my SM-G900V using Tapatalk

 

[Kadonny]

Glad everything is working on you rifle and you are enjoying it. Each person's zero preference is purely that, a preference based on your needs. For me and how I practice and for any SD scenario, I like my 100 yard zero because it simplifies aiming. All I ever have to worry about if not a 100 yards is how much holdover to use whether it be under 100 yds or over 100 yds. It really simplifies things.

 

[shep854]

Remember to keep the height of your sights over bore in mind, especially for barricade and REALLY close shooting.

 

[Tbat]

Hey dudes, couple of quick updates.

1) The rifle works, so that tiny spring is pretty much confirmed as not being from the gun.

2) I was definitely under-educated on sight zeroing, and after the extremely helpful posts here I would like to think that I am better informed.

While I did get a chance to fire it this past weekend, I didn't really have the chance or the right gear to zero in my sights properly. I forgot my rifle rest, and was backyard shooting so didn't have any way to conform the 50 yard target distance. With all that said, the iron sights seemed to put the bullet pretty damn close to where I was aiming so the factory zero was good enough to have some fun.

Next trip to the range I'll actually take my time to do a proper 50 yard zero, I think that's the most practical option for me at the moment.

Sent from my SM-G900V using Tapatalk

You don't need a lot of extra gear to get your rifle zeroed at 50 yards. Get down on the ground and shoot from the prone position and you will be stable enough to get a good zero, if you watch your sight picture, breathing, and trigger control.

If you don't have access to a 50 yard range you can get a 50 yard zero at 10 yards, point of impact should be about 1.9 inches below point of aim at ten (10) yards in order to be on at 50 yards. Then you can confirm and make any fine adjustments when you get to a 50 yard range. This works with 16 inch carbines, with standard height sights. I have tried it a few times with no issues. [ame]https://www.youtube.com/watch?v=P-FUsH8jt6E[/ame]