TL;DR, see my major conclusions   Before we get started, for those who are not familiar with how to use the 2x fixed-zero Rifle Optics in the first place, see the "Sight Usage" section of Dslyecxi's TTP3, about 40% of the way down under "Basic Infantry; Combat Marksmanship; Basic Marksmanship" http://ttp3.dslyecxi.com/2_basic_infantry.php   Now, since the earliest parts of the early access period, Arma 3 has had a series of 2x-and-a-bit magnification optics with fixed 300m zeroes and ballistic drop compensators. There were (and to a certain extent, still are) a lot of assumptions going around about these optics. That some are for certain calibers. That 7.62mm NATO has no corresponding optics. That any optic "in a certain caliber" would match up with any weapon in that caliber. Kind of makes sense, right? That because the RCO (MX) and ARCO (Katiba) were both found on 6.5mm weapons, they were interchangeable and that any 6.5mm weapon would work with them. Same for the MRCO (Mk20), ERCO (SPAR-16), and 5.56mm. And because none of them came with 7.62mm weapons as their "obvious" partner, big bore was -poop- out of luck for 2x optics.   But I've been watching a lot of Rogue-9's videos regarding mechanics investigations in Rainbow Six Siege recently, and every single time he does in with assumptions, they get busted (side note, go sub to him if you have any interest in Siege, his work is very informative). This started getting me thinking about some of the assumptions I had about Arma 3, and the 2x Rifle Optics was one of the biggest ones. So I loaded up Hebontes, and after some trial and error getting the target ranges right, I loaded up my rifles and started plinking.   The results were... well, native English speakers know what they say about assumptions: they make an Ass of U and Umption   For those who just want the results, here's a link to the documents I wrote up about    General Recommendations and Conclusions https://docs.google.com/document/d/1urGglgS6M_d26dFl3nynFDkGbUSdRvqgvw2tsCgONxw/edit?usp=sharing   Recommendations per Weapon https://docs.google.com/document/d/1v4a5em93QRZodoPky1dW0Vl4_9pGlB_3MXoj9BUTN_s/edit?usp=sharing   Testing Data per Optic https://docs.google.com/document/d/1bUjriRrR7xVe7XSViNZxnhE4siJ3tZabByN2Xn-v8_M/edit?usp=sharing   Pictures are not included since most of you should already know darn well what each optic and reticle look like by now   Testing Procedure   First major conclusion: The only weapons that work flawlessly with any optic are the ones they are paired with. RCO-MX Carbine ARCO-Katiba Rifle MRCO-TRG-21 ERCO-SPAR-16S Beyond that, any example of consistently acceptable performance was down to ballistic characteristics being sufficiently similar   Second major conclusion: Within 400m, it really does not matter. Within 500m, only for particularly fast or slow weapons will the markers be incorrect. By extension, any of the 200m reflex sights as well as the NVS will be just fine within their limitations   Third Major Conclusion: The only optics that are truly hassle-free are those with adjustable zeroing. If you have the choice, I'd recommend the DMS over any of the 2x fixed optics, as it offers several advantages (4x, idiot-proof rangefinder, adjustable zero 100-1000m, etc) with the only disadvantage being unable to be used with NVGs. Of course, the Nightstalker is also available, but the Nightstalker is more likely than not to be unavailable, and it's kind of a bit too easy in my opinion (so much so the US Army is trying to copy the concept with FWS-I)   Fourth Major Conclusion: While the long-barreled marksman rifles (MXM, Mk-I, CMR-76, SPAR-17) can make use of 2x optics, they are really much better suited for adjustable-zero. I'd recommend either the medium range (DMS, MOS) or medium-long range options (AMS, Kahlia). The other 7.62mm rifles, however, are well set for certain 2x optic combinations should you chose to go that way   Final Major Conclusion: My recommended optic combinations. These combinations require no (optimal) or little (good) adjustment to achieve consistent hits within their effective range. Grenade launcher variants are included with their rifle and carbine counterparts   RCO Optimal: MX Carbine, SPAR-17, CAR-95, CAR-95-1, Navid, Mk20 Rifle, Mk20C, Mk18 ABR, TRG-21   Good: MX SW, SPAR-16, SPAR-16S, TRG-20, LIM-85, Mk14   ARCO: Optimal: Katiba Rifle, Katiba Carbine, MX SW, Mk-I EMR, CAR-95, Navid, Mk20 Rifle, Mk18 ABR, TRG-21, LIM-85   Good: MX Carbine, MXM, SPAR-17, CAR-95-1, Type 115, Mk14   Acceptable: Mk200   MRCO Optimal: CAR-95, TRG-21, Mk14, Katiba Carbine, Mk18 ABR   Good: MX Carbine, SPAR-17, CAR-95-1, MXC, Katiba Rifle   ERCO Optimal: SPAR-16S, SPAR-16, TRG-20, Mk20C, MXC, Rahim   Acceptable: AK-12 (50m slow @500m, 100m@600)   Adjustable Zero (DMS, MOS, AMS, etc.) Recommended: MXM, SPMG, MK-I EMR, SPAR-17, Type 115, Zafir, Navid, Rahim, CMR-76, Mk200, AK-12, Mk14     Special Note: Zafir has varying degrees of front sight blockage with any optic other than RCO, which isn't a good match anyhow. Also, ERCO has some front sight blockage with some weapons, namely the Navid, Mk-I, and SPMG   I hope you found my investigation useful. I certainly have. Thanks for reading, and I'll see you on the battlefield    For those interested, a link to a similar investigation I did for the AT launchers https://docs.google.com/document/d/1oGznRhgYVCrSSCgKP8ZcB-Q9aQCMJVo94tmPjEvml_o/edit?usp=sharing