Posted: 2/22/2007 9:20:16 PM EDT
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I bought a PCR at the WAC show in January. I finally got a chance to shoot it last weekend and I had a heck of a time sighting in. My other upper, the ML-2, took about 8 rounds to get sighted in on the dot, but this one started out WAY high and to the left at 50 yards. I got the windage squared away pretty quickly, but the elevation was another story. All of my rifles are sighted in at 50 yards, as most game I've taken has been between 30-65 yards. If you include coyotes, most of those were taken at under 40 yards. The rear A-2 sight was already bottomed out when I started shooting, so my only option left was to raise the front sight post. I raised it to the point that I was concerned that it would fall out, and it was still about 3" to 4" high. I will likely use the A-2 sights only as a back up, and install a red-dot sight on it, but I want to get them zeroed before I go to the trouble of mounting and sighting in the red-dot. Any suggestions on fixing this issue? Thanks! |
A few questions...forgive me if seem like I am challanging your intelligence, but I would rather cover all of the bases here. I'll assume the ammo is all the same bullet weight? lot/manufacturer? IS this an A-2 config upper or are you referring to an A-3 detatchable carry handle? Did you start at mechanical zero before zeroing, or did you just shoot whatever was already set? Either way in the case of a fixed or detatch...all of your elevation adjustments when zeroing come from the front sight post, not the elevation for the rear sight. The M16/AR rifle (A2 series) is generally designed to be zeroed at 25 meters, then elevation adjustments made for 400, 500, 600, 700, 800 (As well as varying increments inbetween) The "zero" position for the 25 meter zero is one click past (under) 300 or the "8/3" setting. For the A-3 series detach handle, most that I have seen ARE designed for the carbine barrel and marked and graduated for 300-600 meter settings. The zero setting is designed for 25 meters, but the zero position is generall 2 clicks above 300 (The "6/3" mark) and is enumerated by a "Z". Another point to note is that the zero target IS different for the A2 and A3...the graduations are different in reference to sight adjustments. If all of the above does not apply, then by all means..replace the front sight post with a taller one.  AND THEN THERE'S THIS.............. Tweak338 Team Member PRK Resident <-----------------------------------------  Joined :: July 2005 Post Number :: 69 CA, USA <<<<<<-------------------------------------------  Either you are an "infiltrator", really stupid, or extremely resilant.  The fact you know PCR rules out 2 of the 3.  |
So why doesn't Oly make that standard on Carbine barrels? 
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Because Oly is not Colt. 
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Bingo!  Bushmaster doesn't do it either and it's rather stupid and irritating. My A2 is borderline needing the taller FSP, just been too lazy to order it. My other Bushy barrel(on an A1 upper) didn't come with the FSP at all so it got the taller one, didn't need excessive adjustment elevation wise. Imagine that. |
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RTFM Olympic Arms PCR TM 9-1005-319-10, The U.S. Army Operator's Manual for M16 / M4 Improved Battlesight Zero by LTC Chuck Santose Zero an M16A2 Rifle As Matt45 stated, these things usually get sighted in at 25 METERS, per the way he described. Use this target to make life easier:  Right-click, save as. Then print it out on 8.5" x 11" paper. If you've got a laser printer, bonus! |
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Thanks folks. I have a taller front sight base on order, and I didn't take offense to anyone's suggestions. That is why I asked. The rifle is an A-2, and I tried a number of things suggested, but I'm hoping the talle front sight base works. If that doesn't, I guess I can always plane down the base of the rear sight. I love my Oly parts, so don't be a hater.  Only issue so far is sighting it in, but I attribute that in part to user error. Everything else is as dependable as can be expected.I understand sighting them in at 25, but all of my other open sighted rifles are zeroed at 50. |
From AFMAN 10-100 / 1 June 2004, The Airman's Manual:
Remember to use the smaller aperture when sighting in and for general shooting. Only use that "0-200 meter" larger aperture for CQB, shooting while wearing a gas mask or shooting at night. |
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In regards to the differnce between 25 meters and 50 yds, as far as the .223/5.56 goes, it's extremely negligable. I'd wager that there is not much discernable difference between the ponit of impact (POI) Vs. the point of aim (POA). FWIW, Army folks are taught to shoot 25, 50, 70, 100, 150, 200, 250, and 300 meter targets without changing a thing other than POA. JS...that's a very cool short list for the M-16/AR...now do you think mebbe, just mebbe you can dig up a JPEG of an M4 zero target??? Preese?
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The military improperly released the M-4 data package to the industry. Colt went to court and successfully blocked manufacturers from using any of the information contained in the M-4 data package. That's why. Companies like Bushmaster and Oly had to adapt A-2 technology to their M4geries. That's why things don't always quite line up the way they should. It's not that they can't do it, they are just legally restrained from doing so. Some parts makers seem to be getting around it, but they don't make rifles. Colt keeps their eyes on Bushmaster, Oly and a few others. |
Duh, just flip it over!  ETA: The targets I have in PDF format. M16A2 25 Meter Zero Target M4 50 Yard Zero Target M4 50 Yard Improved Battlesight Zero Target 1000 Inch (25 Meter) Target |
Taller front sight posts have been a solution long before the M4. COLT's claim is the FSB, which uses a standard front sight post instead of a taller carbine post used in a rifle FSB. Carbines are known to have issues zeroing with a standard front sight post in a rifle front sight base, that is why COLT used a taller front sight post way back in your day So other manufacturers COULD use a taller front sight post, they just choose not to. They even make the part 
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