[9] However, a notable design feature is the use of a locking breech block within the slide utilizing the "hesitation-locked" action originally developed by John Pedersen.

[4][10] When the pistol is in battery, the breech block rests slightly forward of the locking shoulder in the frame.

[10] The R51's low bore axis gives less muzzle rise which also lowers perceived recoil, while the stationary barrel improves accuracy and simplifies construction.

Initial production took place in Pineville, a suburb of Charlotte, North Carolina at Para USA, one of Remington's family of brands in late 2013.

However, they praised its compact size and "inspired aesthetic", saying that "for a couple hundred bucks, this gun is totally worth it.

"[15] Similarly, American Rifleman complained of poor quality magazines which often failed to load properly, but noted its good accuracy and modest price.

[16] The Firearm Blog was more critical, claiming that for a weapon of its size, a 7-round magazine capacity was too small, and it was much too difficult to field strip: "taking the R51 apart for cleaning might be the worst experience of my life, but it's a one time affair.

After you field strip the R51 for the first time, I promise you will either sell the gun, or just run it dirty until it kicks the bucket."

The Firearm Blog owed most of the R51's problems to its grip safety, which would pull the shooter's aim down and towards the right, and mentioned that the first 200 rounds were a "disgrace", with many malfunctions, including the magazine falling out, failure to feed, failure to extract and stovepipes, and claimed "I don't think I've ever shot something that was quite so uncomfortable.

"[17] After the voluntary recall in 2014, Remington went back to the drawing board to fix the issues reported by critics and owners.

Nearly two years later, on 23 June 2016 Remington began to ship the new updated version, commonly known as "Gen 2", to original owners that sent their handguns in for replacement.

In the 2017 Remington catalog the R51 was shown to have the following "enhanced" features: Enhanced slide operation - updated internals ensure superior slide performance and smooth function, Precision engineered extractor - built to withstand abuse, extractor precisely engages case rim for sure and forceful extraction and ejection, Snag-free sights - locking snag free sights for fast target acquisition, Finely-tuned recoil spring - force-balanced for impeccable slide feel and positive closure into battery, Action spring bushing - hard chromed action spring bushing for extreme durability, Superior trigger - crisp, single action trigger improves shootability and enhanced accuracy.