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AR rear sight questions

Discussion in 'Rifle Country' started by Detritus, Nov 5, 2007.

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  1. Detritus

    Detritus Member

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    as part of a general plan of upgrades, i am thinking of replacing the rear sight (the L-shaped apperture piece) on my wife's A1 style AR, since the factory unit on the Oly Plinker Plus upper kinda sux. but i have been unable to determine what a legit "original spec" A1 rear sight is supposed to look like. b/c i some how doubt that the spec calls for a flippable two apperture sight system with both appertures the same size and same "height above bore".

    so anyway here's my question.

    1. what IS the "real M16A1" rear sight supposed to look like?
    2. Who if any one currently makes or sells one.
    3. If 2=no then will an A2 style fit the A1 type windage screw?

    thank you for your time, as always any and all advice, info, and input is appreciated.
     
  2. Chris B

    Chris B Member

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  3. ugaarguy

    ugaarguy Moderator Staff Member

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    I just checked my Oly Plinkster upper against my early 80s Colt SP1 and the rear sight apertures are identical. The size difference of the two apertures is minimal on A1 rear sights. The A2 apertures have a much more pronounced size difference, with the short range aperture being much more open. If you order an A1 rear aperture assembly from another maker you won't see any difference from what you currently have. You can put an A2 aperture in there though and it should help with the sight picture in reduced light.
     
  4. Detritus

    Detritus Member

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    well, guess i'll get an A2 apperture assembly then. b/c my expereince with the unit on my oly has been rather dismal, I find the apperture size on my example to be "just about the wrong size for any use I have for it" as in too large to be a target size and too small for a "combat sight".

    I'm hoping a better rear sight setup and a RRA 2-stage trigger will make it easier for my wife to use it and possibly reduce her group size a little.

    frankly, to make any major improvement, i think it actually needs a new(different) barrel, the only rifle i've owned that shot worse at 50 yards was a very battered No4Mk1 Enfield with a buggered up crown and what i now beleive to have been a bad spot in the throat.
    But i'm trying the cheap changes i'd be making anyway, first to see if they help.
     
  5. Bartholomew Roberts

    Bartholomew Roberts Moderator Emeritus

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    I would get a same plane aperture instead of an A1 aperture. With the A1 aperture, your zero will change whenever you flip from the large aperture to the small aperture or vice versa (the idea being that the small aperture is for long range and the large aperture for up close).

    I prefer to zero same plane apertures at 50yds. This gives me +/- 2.6" from point of aim all the way to 250yds and about 6" of drop at 300yds using 55gr M193. This makes use of irons to 300yds simple and straightforward and you can still use the small aperture for small targets closer than 300 without changing the zero.

    Downside is most same plane apertures use fairly large apertures compared to the A1 for the first aperture, so if you aren't liking that on the A1, you really won't like it on the A2 style large aperture.
     
  6. DMK

    DMK Member

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    I own two surplus M16A1 uppers. The close and long range apertures are the same exact size. One is slightly higher than the other, but it's not apparent unless you measure with a calipers.

    I ended up replacing mine with M16A2 apertures (and front sight post) then zeroing with the small aperture at 50 yards(200m IBZ). That leaves me with a large aperture zeroed for up close use and well within minute of pie plate out at 100 yards.

    On my carbines I use the same plane sights that Bartholomew Roberts refers too. They are expensive ($25 vs. $5-$10 for an M16A2 sight) and you do lose some precision. On the other hand, you get a small aperture that's more precise than the M16A2 Ghost aperture, but allows quicker target acquisition than the M16A2 or M16A1 small aperture.
     
  7. Detritus

    Detritus Member

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    actually i got no problem with the apperture being big (with an A1 upper it'll never see a CMP or similar match). my problem is that the Oly factory piece can't seem to make up it's mind as to what it should be, the appertures don't split the difference between a Ghost Ring and a correctly sized "target apperture" there just some seemingly random size (maybe what ever drill was sharpest/handy that day??).
    and unlike ugaarguy mine does not match up well to a legit A1/SP1 rear sight. i just stopped by my local "real gunshop" and took a look at the two SP1s in his rack, and on the one that i KNOW hasn't been monkeyed with, the appertures are slightly larger as well as being.... I don't know if the phrases "cleaner, sharper, and better finished" convey what i mean but they'll have to do b/c i don't know how else to say it, maybe "more like the 60-70 year old Lyman receiver sight i used to have, in the way of sight picture"?.

    Ok so i'm a little bit of a spoiled and picky Bast@%&, but i'm trying to get the most out of this rifle for my wife and as i think i said before i want to remove as many of the possible impediments to it being able to shoot well as i can. and I find the sights to be limiting in a certain way.
     
  8. Detritus

    Detritus Member

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    Ok and there's a change from my example, flipping from one aperture to the other does not have any decernable effect on point of impact, i think that Oly may have found some cost related reason to have both "sides" identical.

    then again the barrel may just be that much of a POS and i can't tell the impact change cause it throws em over such a wide span anyway. time and small parts changes will tell:)
     
  9. ugaarguy

    ugaarguy Moderator Staff Member

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    I'm just curious, what's the twist of the barrel in your Plinkster, and what weight bullets are you shooting through it?
     
  10. Zach S

    Zach S Member

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    I'd reccomend an A2 aperture, or an XS same plane.

    All of mine have A1 sights with A2 apertures. XS planned for my 5.56, but I'll leave the A2s on my pistol cals.
     
  11. sully

    sully Member

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    An A1 aperture has two holes that appear to the be the same size. One has no markings on the base, while the other has "L" marked on the base. The one with no marking is your 0-200m aperture, and the "L" marked aperture is for 300m-800m.

    An A2 aperture has a large hole and a small hole apertures. The large hole is marked 0-2 which is designed for 0-200m ranges. The small hole has no markings and is for 300m-600m for short sight radius weapons, and for long sight radius weapons 300m-800m.

    What people don't realize is that generally when you switch from the 0-200m aperture to the long range aperture it will raise your zero approximately 6.5" at 100yds. Both the A1 and A2 style apertures have the same thread pitch so they are interchangable. On our SLR15 line of rifles I prefer to use same plane apertures where there is not change in zero at any distance.

    CY6
    Greg Sullivan "Sully"
    http://www.SLR15.com
    http://www.TheDefensiveEdge.com
     
  12. Detritus

    Detritus Member

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    barrel is unmarked but it is supposedly (according to customer service at Oly i asked b/c of no markings) a 1in9. all but the first 60rds have been surplus Radway Green, that's 62gr correct?
    I do plan on going back and seeing how it does with 55gr pills before i take the step of replacing the barrel. in large part b/c most of my current stash of .224 Dia. bullets are 52 and 55gr.
     
  13. DMK

    DMK Member

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    I love the XS Sight Systems same plane aperture, but I wish someone(especially XS) would make one where the aperture sizes are the same as an A2 sight.
     
  14. DMK

    DMK Member

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    Hmm, it's really unusual for an AR15 to shoot that bad unless it's just been shot out from hard use.

    Is everything tight? Does yourfront sight post wiggle? How about the rear aperture. It should be tight (shouldn't move left/right or up/down). Is the crown dinged? Is the rifling worn at the muzzle?

    It could even be that the barrel is torqued down too tight, or even loose.

    I've never shot any myself, but I've heard complaints about Radway surplus on the Interwebnet. Have you tried anything else? Even some Walmart Remington FMJ should shoot no worse than three or four inch groups at 100 yrds.
     
  15. ugaarguy

    ugaarguy Moderator Staff Member

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    To my knowledge all Oly barrels are 1:9 unless otherwise marked, so that does sound correct.
    It should be. Radway makes NATO Spec ammo for the Brits, and the 62gr steel core M885 has been NATO standard for quite a while. Does it have green paint on the tip?
    The 1:9 twist should stabilize anything from 50 to some where around 67 grains equally well. Someone here will be able to tell you what the heaviest bullets it'll stabilize are. Anyway, it shouldn't have a problem with 52 and 55 gr. stuff.

    I'd also check everything DMK lists in his last post, starting with the ammo. Could be your surplus Radway was a bad lot. If different ammo doesn't fix it he's given you a great list of things to look at.
     
  16. Detritus

    Detritus Member

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    No but it's all early '90s headstamps, and i've been told/heard a number of times that not all Brit M885 got painted, since for the most part they sort of Started with M885 and didn't really NEED to have a visual cue for which is 62 and which is 55gr ball.

    I'll check this if an ammo change doesn't help, but if so then Oly's QC Dept is WAY behind the eightball! they had two bites at that apple. once when the upper first shipped and again when i sent it back b/c i ran out of windage trying to Zero the thing.
     
  17. Jeff White

    Jeff White Moderator Staff Member

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    Only the US and Israel paint their M855 spec ammo with a green tip. Nobdy else fields a large amount of both 1/7 and 1/12 twist rifles.

    Jeff
     
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