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

[Rastoff]

Did you check your sights? Do you have a QD mount?

 

[Cantthink0f0ne]

Did you check your sights? Do you have a QD mount?

Checked the sights, fixed front sight has the detent and pushes down properly, flip up rear sight is functional and windage adjustment clicks well. Don't have any accessories on it yet, it's bare bones stock, so no QD mount that it could have come from.

I've come to the conclusion that the spring isn't from the rifle.

Thank you for the replies!

Sent from my SM-G900V using Tapatalk

 

[Kadonny]

It has to be extra. That's a really short spring that wouldn't fit most of the parts people have listed except maybe the bolt extractor spring. Even this I think might be thinner and not as fat as that spring in your picture.

 

[Cantthink0f0ne]

Cycled some dummy rounds and expectedly everything works properly.

Quest for you guys, how many rounds do you recommend I go through before zeroing in my sights?

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[cyphertext]

Cycled some dummy rounds and expectedly everything works properly.

Quest for you guys, how many rounds do you recommend I go through before zeroing in my sights?

Sent from my SM-G900V using Tapatalk

One... fire the first one to see where it hits and go from there.

 

[Rastoff]

Quest for you guys, how many rounds do you recommend I go through before zeroing in my sights?

That's a loaded question. There are a lot of theories on how to zero rifle sights.

What I've always done:

• Use sand bags for support or some other kind of support. This will reduce shooter-induced-movement as much as possible.
• Fire one or two rounds to foul the barrel. The first shot on a clean barrel will almost always be a flier.
• Fire a three shot group. Take your time with each shot and make it as precise as you possibly can.
• Examine your group and make adjustments based on the center of that group.

I've attached an excellent target for this process. It has squares that are 1MOA at 50 yards. Remember, when making adjustments, the marks on your sights are for moving the group.

Here's an example of how to use the attached target:

The red dots are the three shot group you just shot. The amount you need to move is noted on the sides and top of the target. If you look in each corner, in this case the top right corner, there are letters indicating how you should move the group.

Fire one more three shot group. The center of the group should be in the center of the Target. If all three shots are in the green circle, don't attempt to adjust it any more. This is the limit of the precision of your sights. If you've taken your time, this should be the only time you need to adjust it.

I'm sure this is more that what you were asking, but there it is.

 

[Cantthink0f0ne]

That's a loaded question. There are a lot of theories on how to zero rifle sights.

What I've always done:

• Use sand bags for support or some other kind of support. This will reduce shooter-induced-movement as much as possible.
• Fire one or two rounds to foul the barrel. The first shot on a clean barrel will almost always be a flier.
• Fire a three shot group. Take your time with each shot and make it as precise as you possibly can.
• Examine your group and make adjustments based on the center of that group.

I've attached an excellent target for this process. It has squares that are 1MOA at 50 yards. Remember, when making adjustments, the marks on your sights are for moving the group.

Here's an example of how to use the attached target:

The red dots are the three shot group you just shot. The amount you need to move is noted on the sides and top of the target. If you look in each corner, in this case the top right corner, there are letters indicating how you should move the group.

Fire one more three shot group. The center of the group should be in the center of the Target. If all three shots are in the green circle, don't attempt to adjust it any more. This is the limit of the precision of your sights. If you've taken your time, this should be the only time you need to adjust it.

I'm sure this is more that what you were asking, but there it is.

This is an extremely helpful explanation, thank you! 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.

Sent from my SM-G900V using Tapatalk

 

[cyphertext]

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

 

[sgtsandman]

The above target is used to do a 50 yard zero, which happens to be the most flexible zero for the AR15 with iron sights. It gives you a point of aim that will impact with in the kill zone out to about 225 yards without needing to do any kind of adjustment or hold over. If I remember correctly, the rant is high to low by 2 inches or less throughout that entire yardage distance, with the exception of shots at 25 yards or less. You will need to hold high to compensate for the height of the sights over the barrel. If you don't, you will hit low.

This only applies to iron sights and maybe a red dot. Use whatever the manufacturer recommends as a zero for a scope.

EDIT: This post is for the target posted above the one Cyphertext posted.

EDIT: EDIT: Corrected yardage range of the zero.

 

[shep854]

Oh, you've just opened another can of worms when you ask about sighting in!! ��
The above method works; if distance is limited, 25 yd will do for starters. Lots of shooters like 5-shot strings, to confirm tight groups. There are tons of videos on YouTube, including instruction on methods used by the military.
Whatever method you choose, be as consistent as possible with your shots for best results.
Now, be safe and HAVE FUN!��

 

[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.