Gunner Wade on Boresighting an RCO with issued collimator

We previously covered 2nd Mar Div’s Combat Camera productions involving Gunner Wade and suppressor Fact or Fiction series, but the 2nd Marine Division Gunner is back at it again, this time he is covering how to properly boresight a service rifle and RCO using an issued collimator (although he is using his personal rifle in the video). The process is extremely simple, but if done incorrectly, can result in a very long day of zeroing. After inserting the device in the muzzle of an M16A4, M4, or M27, essentially there is that little diagram inside the collimator, that lines up within the RCO or SDO, and Marines have to match up the 100 meter marker that is the tip of the red chevron (“tip of the d**k” as we say in the Infantry) to the proper diagram within the collimator. However, the video is somewhat misconstrued because this is truly only half the process of zero. The other half involves actually shooting 10 rounds (2 groups of 3, then 1 group of 4 to confirm) at 25 meters to get the RCO or SDO zeroed properly, then another group at 100 meters to get the 100-meter confirmation.

I do like how the video so casually makes a note that spotting scopes and collimators can be requested at Division armories as if any Marine stationed at Camp Lejeune can simply send an e-mail and have a collimator ready at weeks notice or so.

The video is extremely well produced using animation to properly illustrate what the camera cannot capture. Overall, I’m somewhat jealous that these videos are out now, as they could have been extremely useful to Marines of previous generations.

Before this collimator was issued, the Marine Corps used a laser bore sight unit, which used to be an absolute hassle to put together because it tended to be so intricate.


Infantry Marine, based in the Midwest. Specifically interested in small arms history, development, and usage within the MENA region and Central Asia. To that end, I run Silah Report, a website dedicated to analyzing small arms history and news out of MENA and Central Asia.

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  • Spencerhut

    Best branch of the military and we are continually the last to get everything. Oh well, we have always made due and then some. Glad to see such an on the ball Marine helping out everyone.

  • Dougscamo

    When I seat the prisms at the range during sight-in, people look at me like I am deranged….glad to see the Gunny demonstrate that technique….
    Of course if you use James R’s hammer, you are deranged…

    • Russ Kell

      Heh. Right there with you. I’ve setup a few ACOGs for friends when they won’t believe me about tapping the turrets.

  • DrewN

    I have both a collimator (not as nice as that one though) and the laser , and IMO both work just fine. You still need to get everything level, but swapping pilots really isn’t a big deal and it’s dead easy with either to get into the black first shot, never mind just on the paper. I’m not even sure how you could be off a standard target at 25 meters even if all you have are MK 1 eyeballs.

  • Risto Kantonen

    I like how the armed forces are communicating with the rest of the world with combat camera efforts. We got the same thing here in Finland and it’s awesome, FDF has a youtube channel where they upload their combat camera stuff. Effective security and defence requires the cooperation and communication of all areas of society, so this is good development.

  • I’ve handled one of those on a rifle, those collimators are really nice. I really wish they were available on a civilian market, I would probably splurge and buy one.

  • BeGe1

    “Marines have to match up the 100 meter marker that is the tip of the red chevron (“tip of the d**k” as we say in the Infantry)”

    …what? Tip of the d**k is the tip of line below the chevron (i.e. 300 yard aiming point), not the tip of the chevron (i.e. 100 yard aiming point).

    I’ve consistently heard it that way in boot camp, SOI, and infantry units themselves.

  • mazkact

    Well, I just pop the upper off,remove the bolt carrier,bag the upper and look down the bore to bore sight. Works great and I always have my tools, hands and eyes, some kind of object to witness on.