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Primary Arms Prismatic Proliferation

Primary Arms is no stranger to a prism scope, and each generation has improved upon the last. This year we’ll see the Gen III (rollout delayed by COVID) which will be part of their new “standard-tier” line of optics. While all of them (1x, 2x, 2.5x 3x, and 5x) are being refreshed, we got our hands on a 3x 300BLK/7.62×39 model and a 5x 5.56/.308.

Because what we received were preproduction samples, we can’t make any commentary on the packaging — it’s not like we actually care how it looks on a shelf, just how they perform. But bear in mind that there may perhaps be some minor differences between what you see on these pages and what’s on the shelves (hopefully by the time of publication); such is the nature of preproduction samples.

Primary Arms Prismatic Optics


There are more similarities than differences between these two new prismatics, the main one being the slightly larger size of the SLx 5x which has an objective lens 4mm larger (36mm versus 32mm) and is just under a ¼-inch longer. With that size increase comes a weight kick a hair under 2.5 ounces.

Just as with the SLx Gen II models, Primary Arms tells us they spent some more time on the mounting system itself. The fixed mount features hardened steel crossbolts and a removeable spacer for ease of use on either an AR-height rail or a rifle with a lower mounting system such as an AK-type. If you have an ACOG mount you’re in love with, you can simply swap out the factory mount.

The 5x model features five levels of illumination in two colors (red and green) with an “off” function between the two. The 3x model sports 11 brightness settings with a single reticle color. While you probably won’t be blown away by the 3,000-hour battery life, because they’re prismatic sights they’ll still work sans batteries.

The eye box of the 5x SLx is slightly more forgiving than the 3x, but with either you’re not going to be mounting it further along the rail.

In terms of durability, Primary Arms tells us they each survived in excess of 6,000 rounds of .308 from the notorious optic-killer SCAR 17s.


Primary Arms is known for their ACSS bullet-drop compensator (BDC) reticles, so we were unsurprised to see the same in these. While we’re not huge fans of the BDC in most circumstances, you can still make use of those stadia with a little planning (see “No True Zero” in RECOIL Issue 35 for more details). What’s paramount with any BDC is to go out and test/track your own rifle and load at range with the reticle itself. 

Primary Arms Prismatic Reticle

The SLx Gen III 5x is available with the ACSS 5.56/5.45/.308 and also the ACSS Aurora, which was only previously available on special models of the Trijicon ACOG. For the 3x, you can choose between the ACSS-5.56 CQB M2 or the ACSS-CQB 300BLK/7.62×39.


Like previous models, there’s a removable Picatinny top rail on the SLx if you want to piggyback an MRDS or similar for up-close use. Though prismatics, in general, have been used for decades with both eyes open, it can take a lot of practice. Just as with a Trijicon ACOG, you can use what’s called the Bindon Aiming Concept or occluded eye shooting for up-close work.

The idea is that if you have a bright enough reticle and keep both eyes open, your brain will superimpose the reticle your dominant eye is viewing onto your non-dominant eye. The Armson OEG, famously seen mounted on a MACV-SOG rifle during the failed Son Tay prison rescue in 1970, worked in a similar way though the Armson OEG itself couldn’t be seen through.

As you may anticipate, there can be some issues. Optical phoria is a condition that exists when normal binocular vision is interrupted — your eyes move slightly independent of each other. Much of this depends on the physical shape of the eye, and the only way you’ll know if you have any lateral offset is to hit the range and try it yourself. Many folks find flipping the front cap down makes it easier — or just stick an MRDS on the top Picatinny rail, which is undoubtedly why it’s there in the first place.


Red Dots, Prismatics, and More on Optics

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