Primary Arms MRSc Red Dot Review [2023]

Taurus 856 TORO Primary Arms MRSc

After receiving the Taurus 856 TORO for review I needed an optic to go on it. My go-to was the Holosun 407K thanks to past experience. Unfortunately, I wasn't able to get a proper zero, as the Holosun lacked enough elevation adjustment. This experience wasn't a one-off, as several other shooters report the same problem with their Holosun and 856 combinations. This led to me to seek out alternatives, with the Primary Arms MRSc presenting an affordable option. How has the Primary Arms MRSc compared over the past several months?

Construction and Use of the Primary Arms MRSc

The Primary Arms MRSc is a fairly standard pistol mounted optic. It features an open emitter, with screws going through the body to attach it to a slide or mount. Using a Shield RMSc footprint, the MRSc should fit on most slimline optic cuts, and the Taurus 856 TORO.

Battery Life and Function

The Primary Arms MRSc gets its power from a single CR2032. This is loaded into the optic directly through the bottom of the MRSc, much like the Trijicon RMR. There is no sealing plate here, though I cannot speak to its resistance to moisture. Regarding battery life, Primary Arms claims 40,000 hours in their manual, and 25,001-50,000 hours on the MRSc product page. This of course will vary widely based upon your brightness setting.

Taurus 856 TORO Primary Arms MRSc
Witness mark your mounting and adjustment screws to keep track of any unplanned movement

The optic features on auto-off function which activates after 16 hours. I rarely shut the MRSc off manually, instead relying upon this feature, which reliably functioned throughout review. There is no shake-awake technology here, so you'll need to press the "+" button to turn on the dot when off, or keep auto-off at bay.

Controls and Adjustments of the Primary Arms MRSc

Controls are very straightforward on the Primary Arms MRSc. There are two brightness adjustment buttons, one on either side of the optic. The left side features a "+" button to increase brightness and activate the optic. Pressing the "-" button on the right side will decrease brightness, and holding it for several seconds will shut off the reticle. These buttons have positive clicks, both tactile and audible in nature. Each press gives a noticeable change in brightness, with moderate steps up and down to help find an appropriate level.

Taurus 856 TORO Primary Arms MRSc
The buttons provide tactile feedback with each press

The MRSc remembers your last brightness setting upon activation, which is a nice feature. That said, always verify your brightness before strapping the gun on for the day. With 10 brightness settings, users should be able to find one appropriate for their situation.


The windage and elevation adjustments are probably my biggest complaint on the Primary Arms MRSc. These are simply setscrews, with no clicks whatsoever to discern adjustment. Primary Arms includes a small wrench to make adjustments, so you'll want to keep that handy in your range bag. While I was able to get the gun sighted in at 25 yards, making precision adjustments is very difficult. There is a total of 60MOA of adjustment on the MRSc, with 30MOA in either direction. If I could make one change about this optic it would be to make it click-adjustable.

Reticle and Glass Quality

I was very surprised at the quality of the glass in the Primary Arms MRSc. The glass is incredibly clear, well above any Holosun offering, though not quite to the level of Aimpoint. There is very slight magnification, and a minor amount of distortion near the top of the housing, but nothing to impact function. The 3MOA reticle is incredibly crisp, being one of the finest dots for my eyes to date.

Taurus 856 TORO Primary Arms MRSc
The glass is surprsingly high quality for the price of this optic

Both of these features make the MRSc very pleasant to get behind. I'm extremely impressed in these regards, especially for the price the MRSc goes for. There are plenty of more expensive optics who could take note to improve their glass and emitters to this degree.

Range Time with the Primary Arms MRSc

The Primary Arms MRSc spent its entire life atop my Taurus 856 TORO for this review. Range time consisted of my regular practice and at least double the round count in dry practice. Shooting is a mix of slow-fire accuracy focused targets, and drills such as the Bill Drill and Super Revolver Test. Brightness has been perfectly suitable for the direct Nevada sunlight during Summer. Below is the total round count as of the time of this writing.

Rounds fired: 1,205

  • 10x Inceptor 77gr ARX
  • 10x Hornady Critical Defense Lite 90gr FTX
  • 21x Critical Defense 110gr FTX
  • 4x Federal American Eagle 130gr FMJ
  • 5x PPU 130gr FMJ
  • 25x Fiocchi Range Dynamics 130gr FMJ
  • 5x PMC Bronze 132gr FMJ
  • 27x Federal Gold Medal Match 148gr Wadcutter
  • 50x Winchester Train & Protect 158gr LSWCHP
  • 50x Federal American Eagle 158gr LRN
  • 834x Lawman 158gr TMJ
  • 23x Federal Punch 120gr +P JHP
  • 100x Remington UMC 125gr +P SJHP
  • 20x Federal Hydra Shok Deep 129gr +P JHP
  • 2x Federal HST Micro 130gr +P JHP
  • 19x Speer Gold Dot 135gr +P JHP

Much to my surprise, the Primary Arms MRSc maintained zero despite the lack of click adjustments. Mounting screws also stayed secure, despite some differences in geometry between what Taurus includes and the shape of the MRSc. While not abused, I did repeatedly get the gun and optic too hot to touch, which the dot survived without issue.

Taurus 856 TORO Primary Arms MRSc
Adjustments are made using a small Allen wrench

Having spent its life on a revolver, I cannot comment on the MRSc's ability to withstand forces associated with the reciprocating slide of an autoloading pistol. That said, it appears to be perfectly sufficient for life on a revolver or carbine.

Final Thoughts on the Primary Arms MRSc

Overall I am very impressed with the Primary Arms MRSc. While I would like to see changes made to the zero adjustments, I don't have many complaints, especially for the price. If you're looking for an inexpensive red dot to put on your 856 TORO or a carbine for competition or fun, consider the Primary Arms MRSc.

MSRP on the Primary Arms MRSc is $149.99, and you can find yours >>HERE<<

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About Daniel Reedy 389 Articles
Daniel holds instructor certifications from Rangemaster, Agile Training & Consulting, and the NRA. He has received training from Craig Douglas, Tom Givens, and Steve Fisher among others. He also has experience competing in USPSA, CAS, 3 Gun, and Steel Challenge. In his free time Daniel enjoys petting puppies and reading the Constitution. His work is also published by AmmoLand, Recoil Concealment, and Air Force Times. Daniel has also written and edited for The Kommando Blog.

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