My first AR - Merry Christmas to me!

BigMikey76 · December 1, 2018, 05:32 PM

Been wanting an AR for a while, and PSA's Black Friday deals gave me a price range that I could justify to my wife, so the purchase is made, and I should have it in time for Christmas.
Of course, the idea of adding an AR to my safe is getting me all excited for adding on, customizing, etc. In that spirit, I have a question. I'm looking at a Magpul M-Lok handguard. It has M-lok slots at the 2, 10, and 6:00 positions. Will a rail added to the 2:00 slots line up with a 45 degree offset piece mounted to the top of the receiver? The purpose here, of course, is to have a set of pop up back up sights mounted at the 45 degree offset angle. Will the 2:00 m-lok slots line up right, or am I better off getting a handguard that has a top rail, and adding a 45 degree offset onto it just like I plan to do in the back?

pblanc · December 1, 2018, 06:05 PM

I don't know for certain but I have a strong feeling that won't work. The base of the front and rear sights are going to be on a different axis than the bore, even if they both are oriented at the same 45 degree angle.

What are you planning to use as the primary sighting system?

BigMikey76 · December 1, 2018, 08:24 PM

For primary sighting, I'm planning on a red dot. Haven't chosen one, yet.

pblanc · December 1, 2018, 09:55 PM

Many red dot sights come with risers of the appropriate height to allow you to co-witness regular "iron" sights through the optic tube, so long as they are not magnified.

TJB101 · December 1, 2018, 10:24 PM

Quote:

Originally Posted by pblanc

Many red dot sights come with risers of the appropriate height to allow you to co-witness regular "iron" sights through the optic tube, so long as they are not magnified.

This ^^^^

Some red dots will allow for full co-witness with irons and some may support bottom 1/3 witness .... personally I like the dots higher and have irons available in the bottom 1/3 of the glass.

BigMikey76 · December 1, 2018, 10:29 PM

I'm not looking for magnification, so that could definitely be my answer. The rifle comes with a standard front sight, and no rear. If I'm understanding right, then, I could mount a red dot, and just add a rear sight, and as long as the red dot is at the right height, I dont need to worry about any funky angle mounts?

ms6852 · December 1, 2018, 10:42 PM

I use a 3X prism Vortex Surefire on one of my AR's. It has rails on it where you could mount any accessories to it. Since you are not interested in magnification this is a straight 3 power scope with a red and green sight with several levels of brightness adjustments and the reticle depending on your zero will take you to 600 yards easily. The beauty of this is that the reticle is etched on to the glass should your battery go weak. You can still aim to 600 yards. I really like mine and get be purchased for under $360. BTW congratulations on your first AR purchase. It is really a fun rifle to shoot for the whole family with proper guidance of course.

kymasabe · December 1, 2018, 10:52 PM

My Sig Romeo4c cowitnesses perfectly with my magpul mbus folding sights.

ifithitu · December 1, 2018, 11:24 PM

Congratulations now,and when it come's home.

pblanc · December 2, 2018, 08:08 AM

The standard for AR sights is for the sight line to be 2.5" above the bore axis. For a flat top receiver (no carry handle sight) this puts the rear sight aperture about 1.5" above the top of the Picatinny rail. Rail-mounted rear sights like the polymer flip-up Magpul MBUS are designed for this aperture height so that they will work properly with the standard A2 front sight tower and post.

Most red dot sights that are designed to work with ARs will either come with a riser or will be designed to provide for either an exact co-witness or a lower 1/3 co-witness, or will be designed to accept risers to provide for one or the other, or either.

An exact co-witness is where you flip up your rear sight, look through the aperture and through the center of the optic tube, and the red dot, the top of the front sight post, and the center of the rear peep aperture all line up perfectly. With a lower 1/3 co-witness when you look through the optic the red dot will be seen to be "floating" some distance above the front sight post. You can still use your flip-up rear sight but using the back-up sights you will be looking through the lower 1/3 portion of the optic tube so you need to adjust your eye position slightly downward. Some people prefer one and some the other. Obviously, a lower 1/3 co-witness will require the optic center to be positioned a little higher than for an exact co-witness.

For example, my SIG Romeo 5 RDS (which I can recommend and can often be found on sale for $120) comes with a removable riser to raise the optic 36 mm (1.41") above the Picatinny rail. This provides an exact co-witness with the back-up sights. I also have a 1X Vortex Spitfire which is a non-magnifed prism scope of the type mentioned by ms6852. This comes with a 40.4 mm (1.59") riser which provides for a lower 1/3 co-witness.

Some red dot sights will either come with two different height risers or allow two different height risers to be used with the optic to provide for either exact or lower 1/2 co-witness depending on user preference. An example would be the Primary Arms Microdot.

Mobuck · December 2, 2018, 08:59 AM

"Will a rail added to the 2:00 slots line up with a 45 degree offset piece mounted to the top of the receiver?"
Probably not.
I'm not even sure WHY you want such a set-up. Put a good optic on top of the receiver and learn to use it. This will work for 10 yards or 200 w/o that silly rolling of the rifle to see 45* sights that only a basic guide to aiming(at best).

BigMikey76 · December 2, 2018, 10:50 AM

Mobuck - not necessarily that I WANT such a set up. It's more that I am exploring options, and I have no actual experience with ARs, yet, so I'm looking for info. I have always followed the principle of practicality, which leads me to the conclusion that I should have something to back up the red dot just in case it goes kaput at the wrong time. My search for knowledge started on YouTube, which means most of what I have seen for solutions has come from the tactical-cool school of thought. As usual, I have come here to get the practical alternatives, as well.
At this point, I'll probably just start with adding a standard rear sight and wait on the red dot until I have gotten good with the basics.

pblanc · December 2, 2018, 11:37 AM

If you are looking for a relatively cost-effective rear peep sight to put on the Picatinny rail of an AR the Magpul polymer MBUS is a popular option. This has two different sized rear apertures. The larger aperture is used for closer range shooting as it allows the sight picture to be acquired more quickly. The smaller aperture is better for precision shooting as it allows your eye to more accurately center the tip of the front sight post within the peep.

There are much better and more expensive options than the polymer Magpul MBUS, some of which allow for elevation adjustment at the rear sight for range compensation or zeroing. Most AR flip-up rear sights, including the Magpul polymer MBUS allow only for windage elevation. Elevation adjustments for zeroing will need to be done at the front sight post.

You will benefit from having an inexpensive sight adjustment tool for front sight elevation changes if your rifle did not come with one. You can get by by using a projectile tip or other small pointy object but the tool makes it much easier and is worth the few dollars. You can find them on Amazon and ebay. The original AR sight used a tool that had five little prongs but more modern A2 style sights usually require a tool with four prongs. Some tools have 4 prongs on one end and 5 on the other.

To adjust your front sight post up or down you must push down on a small spring loaded detent which will be at the front edge of the flange on the front sight post. That flange will have either 5 little cut-outs around its perimeter, or more likely 4. The prongs on the sight tool fit into the cut-outs and when you push the tool straight down the detent will be depressed allowing you to rotate the post. Rotating the post clockwise screws it down into the sight body as if it were a bolt or screw. Rotating it counter-clockwise raises the front sight post up. You move the front sight post in the opposite direction you want your groups to move. So if you are zeroing in at 25 or 33 or 50 yards or meters and the groups are low, you want the front post to go down (screw it in clockwise).

How much the groups will move will depend on the exact sight radius of your rifle and whether you have an A1 or A2 type post. It also may vary a bit from rifle to rifle even of the same sight radius. Typically, for a rifle with a carbine length sight radius of around 14.5" one click of rotation (one quarter turn) on an A2 front sight post will move the POI up or down by around 1 3/4 MOA or roughly 7/16" at 25 yards. For a rifle length sight radius of around 20" one click of adjustment will move the POI less, say around 1 1/4 MOA.

If you are new to ARs you can find a wealth of information and misinformation about how to zero your rifle, what zero range to select (which will depend on intended use and ammunition selection), battle sight zero options, and enough other sight trivia to make you want to vomit.

O4L · December 2, 2018, 12:06 PM

Quote:

Originally Posted by BigMikey76

I'm not looking for magnification, so that could definitely be my answer. The rifle comes with a standard front sight, and no rear. If I'm understanding right, then, I could mount a red dot, and just add a rear sight, and as long as the red dot is at the right height, I dont need to worry about any funky angle mounts?

That's correct.

Road_Clam · December 3, 2018, 07:57 AM

On my <100 yd plinker AR-15 upper I have the Vortex Strikefire and a Matech rear sight. The Vortex comes all set up height wise for lower 1/3 co-witness. The Matech are rock solid and I found one NIP off ebay for $40

https://www.surplusammo.com/products...ron-sight.html

Mobuck · December 3, 2018, 08:23 AM

"which leads me to the conclusion that I should have something to back up the red dot just in case it goes kaput at the wrong time"

With the current technology in both "dot" optics and batteries, "going kaput" is a rarity with name brand equipment. If you feel the need for BUIS, go for it but not hanging off the side of your rifle.
You'll find that the 45* offset sights are more likely to get damaged than a good quality dot optic. The offset sights are an offshoot of the "3 gun fad" and as such, are basically like bowling shoes--not good for much else.

December 1, 2018, 05:32 PM	#1
BigMikey76 Senior Member Join Date: December 3, 2011 Location: Bellevue, NE Posts: 981	My first AR - Merry Christmas to me! Been wanting an AR for a while, and PSA's Black Friday deals gave me a price range that I could justify to my wife, so the purchase is made, and I should have it in time for Christmas. Of course, the idea of adding an AR to my safe is getting me all excited for adding on, customizing, etc. In that spirit, I have a question. I'm looking at a Magpul M-Lok handguard. It has M-lok slots at the 2, 10, and 6:00 positions. Will a rail added to the 2:00 slots line up with a 45 degree offset piece mounted to the top of the receiver? The purpose here, of course, is to have a set of pop up back up sights mounted at the 45 degree offset angle. Will the 2:00 m-lok slots line up right, or am I better off getting a handguard that has a top rail, and adding a 45 degree offset onto it just like I plan to do in the back? __________________ Some people are like Slinkies - not really good for anything, but you still can't help but smile when you see one tumble down the stairs.

December 1, 2018, 08:24 PM	#3
BigMikey76 Senior Member Join Date: December 3, 2011 Location: Bellevue, NE Posts: 981	For primary sighting, I'm planning on a red dot. Haven't chosen one, yet. __________________ Some people are like Slinkies - not really good for anything, but you still can't help but smile when you see one tumble down the stairs.

December 1, 2018, 10:29 PM	#6
BigMikey76 Senior Member Join Date: December 3, 2011 Location: Bellevue, NE Posts: 981	I'm not looking for magnification, so that could definitely be my answer. The rifle comes with a standard front sight, and no rear. If I'm understanding right, then, I could mount a red dot, and just add a rear sight, and as long as the red dot is at the right height, I dont need to worry about any funky angle mounts? __________________ Some people are like Slinkies - not really good for anything, but you still can't help but smile when you see one tumble down the stairs.

December 1, 2018, 10:42 PM	#7
ms6852 Senior Member Join Date: April 3, 2010 Location: Texas Posts: 1,394	I use a 3X prism Vortex Surefire on one of my AR's. It has rails on it where you could mount any accessories to it. Since you are not interested in magnification this is a straight 3 power scope with a red and green sight with several levels of brightness adjustments and the reticle depending on your zero will take you to 600 yards easily. The beauty of this is that the reticle is etched on to the glass should your battery go weak. You can still aim to 600 yards. I really like mine and get be purchased for under $360. BTW congratulations on your first AR purchase. It is really a fun rifle to shoot for the whole family with proper guidance of course. __________________ ONLY TWO DEFINING FORCES HAVE GIVEN UP THEIR LIVES FOR YOU. ONE IS JESUS CHRIST FOR YOUR SOUL AND THE OTHER IS THE AMERICAN SOLDIER FOR YOUR FREEDOM.

December 1, 2018, 10:52 PM	#8
kymasabe Senior Member Join Date: June 10, 2005 Location: SW Florida Posts: 2,747	My Sig Romeo4c cowitnesses perfectly with my magpul mbus folding sights. __________________ God's creatures big and small, eat them one, eat them all.

December 1, 2018, 06:05 PM	#2
pblanc Senior Member Join Date: March 23, 2008 Location: Indiana Posts: 697	I don't know for certain but I have a strong feeling that won't work. The base of the front and rear sights are going to be on a different axis than the bore, even if they both are oriented at the same 45 degree angle. What are you planning to use as the primary sighting system?

December 1, 2018, 09:55 PM	#4
pblanc Senior Member Join Date: March 23, 2008 Location: Indiana Posts: 697	Many red dot sights come with risers of the appropriate height to allow you to co-witness regular "iron" sights through the optic tube, so long as they are not magnified.

December 1, 2018, 11:24 PM	#9
ifithitu Senior Member Join Date: May 18, 2016 Location: Derby City KY. Posts: 243	Congratulations now,and when it come's home. __________________ USMC Vietnam Veteran,0311 Grunt. 6/68 to 7/69 Semper Fi

December 2, 2018, 08:08 AM	#10
pblanc Senior Member Join Date: March 23, 2008 Location: Indiana Posts: 697	The standard for AR sights is for the sight line to be 2.5" above the bore axis. For a flat top receiver (no carry handle sight) this puts the rear sight aperture about 1.5" above the top of the Picatinny rail. Rail-mounted rear sights like the polymer flip-up Magpul MBUS are designed for this aperture height so that they will work properly with the standard A2 front sight tower and post. Most red dot sights that are designed to work with ARs will either come with a riser or will be designed to provide for either an exact co-witness or a lower 1/3 co-witness, or will be designed to accept risers to provide for one or the other, or either. An exact co-witness is where you flip up your rear sight, look through the aperture and through the center of the optic tube, and the red dot, the top of the front sight post, and the center of the rear peep aperture all line up perfectly. With a lower 1/3 co-witness when you look through the optic the red dot will be seen to be "floating" some distance above the front sight post. You can still use your flip-up rear sight but using the back-up sights you will be looking through the lower 1/3 portion of the optic tube so you need to adjust your eye position slightly downward. Some people prefer one and some the other. Obviously, a lower 1/3 co-witness will require the optic center to be positioned a little higher than for an exact co-witness. For example, my SIG Romeo 5 RDS (which I can recommend and can often be found on sale for $120) comes with a removable riser to raise the optic 36 mm (1.41") above the Picatinny rail. This provides an exact co-witness with the back-up sights. I also have a 1X Vortex Spitfire which is a non-magnifed prism scope of the type mentioned by ms6852. This comes with a 40.4 mm (1.59") riser which provides for a lower 1/3 co-witness. Some red dot sights will either come with two different height risers or allow two different height risers to be used with the optic to provide for either exact or lower 1/2 co-witness depending on user preference. An example would be the Primary Arms Microdot.

December 2, 2018, 08:59 AM	#11
Mobuck Junior member Join Date: February 2, 2010 Posts: 6,846	"Will a rail added to the 2:00 slots line up with a 45 degree offset piece mounted to the top of the receiver?" Probably not. I'm not even sure WHY you want such a set-up. Put a good optic on top of the receiver and learn to use it. This will work for 10 yards or 200 w/o that silly rolling of the rifle to see 45* sights that only a basic guide to aiming(at best).

December 2, 2018, 10:50 AM	#12
BigMikey76 Senior Member Join Date: December 3, 2011 Location: Bellevue, NE Posts: 981	Mobuck - not necessarily that I WANT such a set up. It's more that I am exploring options, and I have no actual experience with ARs, yet, so I'm looking for info. I have always followed the principle of practicality, which leads me to the conclusion that I should have something to back up the red dot just in case it goes kaput at the wrong time. My search for knowledge started on YouTube, which means most of what I have seen for solutions has come from the tactical-cool school of thought. As usual, I have come here to get the practical alternatives, as well. At this point, I'll probably just start with adding a standard rear sight and wait on the red dot until I have gotten good with the basics. __________________ Some people are like Slinkies - not really good for anything, but you still can't help but smile when you see one tumble down the stairs.

December 2, 2018, 11:37 AM	#13
pblanc Senior Member Join Date: March 23, 2008 Location: Indiana Posts: 697	If you are looking for a relatively cost-effective rear peep sight to put on the Picatinny rail of an AR the Magpul polymer MBUS is a popular option. This has two different sized rear apertures. The larger aperture is used for closer range shooting as it allows the sight picture to be acquired more quickly. The smaller aperture is better for precision shooting as it allows your eye to more accurately center the tip of the front sight post within the peep. There are much better and more expensive options than the polymer Magpul MBUS, some of which allow for elevation adjustment at the rear sight for range compensation or zeroing. Most AR flip-up rear sights, including the Magpul polymer MBUS allow only for windage elevation. Elevation adjustments for zeroing will need to be done at the front sight post. You will benefit from having an inexpensive sight adjustment tool for front sight elevation changes if your rifle did not come with one. You can get by by using a projectile tip or other small pointy object but the tool makes it much easier and is worth the few dollars. You can find them on Amazon and ebay. The original AR sight used a tool that had five little prongs but more modern A2 style sights usually require a tool with four prongs. Some tools have 4 prongs on one end and 5 on the other. To adjust your front sight post up or down you must push down on a small spring loaded detent which will be at the front edge of the flange on the front sight post. That flange will have either 5 little cut-outs around its perimeter, or more likely 4. The prongs on the sight tool fit into the cut-outs and when you push the tool straight down the detent will be depressed allowing you to rotate the post. Rotating the post clockwise screws it down into the sight body as if it were a bolt or screw. Rotating it counter-clockwise raises the front sight post up. You move the front sight post in the opposite direction you want your groups to move. So if you are zeroing in at 25 or 33 or 50 yards or meters and the groups are low, you want the front post to go down (screw it in clockwise). How much the groups will move will depend on the exact sight radius of your rifle and whether you have an A1 or A2 type post. It also may vary a bit from rifle to rifle even of the same sight radius. Typically, for a rifle with a carbine length sight radius of around 14.5" one click of rotation (one quarter turn) on an A2 front sight post will move the POI up or down by around 1 3/4 MOA or roughly 7/16" at 25 yards. For a rifle length sight radius of around 20" one click of adjustment will move the POI less, say around 1 1/4 MOA. If you are new to ARs you can find a wealth of information and misinformation about how to zero your rifle, what zero range to select (which will depend on intended use and ammunition selection), battle sight zero options, and enough other sight trivia to make you want to vomit.

December 3, 2018, 07:57 AM	#15
Road_Clam Senior Member Join Date: November 21, 2013 Location: New Hampshire Posts: 1,695	On my <100 yd plinker AR-15 upper I have the Vortex Strikefire and a Matech rear sight. The Vortex comes all set up height wise for lower 1/3 co-witness. The Matech are rock solid and I found one NIP off ebay for $40 https://www.surplusammo.com/products...ron-sight.html __________________ "To be old an wise you must have been young and stupid"

December 3, 2018, 08:23 AM	#16
Mobuck Junior member Join Date: February 2, 2010 Posts: 6,846	"which leads me to the conclusion that I should have something to back up the red dot just in case it goes kaput at the wrong time" With the current technology in both "dot" optics and batteries, "going kaput" is a rarity with name brand equipment. If you feel the need for BUIS, go for it but not hanging off the side of your rifle. You'll find that the 45* offset sights are more likely to get damaged than a good quality dot optic. The offset sights are an offshoot of the "3 gun fad" and as such, are basically like bowling shoes--not good for much else.