Overview of .22LR AR-15 rifles:
There are basically 6 kinds of .22LR AR-15 rifles.
  •  U.S. Military M261 rimfire adapters for the M16, and clones, such as the Olympic Arms "RFA" Rimfire Adapter and "22-17 Partner"
  •  European CZ V22 rifles and .22LR conversions (previously sold by Victor Arms, and then by ADCO Sales)
  •  AR-15 .22LR rifles and conversion kits from Colt, DPMS (no longer in production) and Bushmaster
  •  Atchisson-style "drop-in" .22LR ADAPTER bolts for upper receivers with .223-chambered barrels, such as those by Ciener and CMMG
  •  AR-15 with .22LR-chambered barrels, with a modified Atchisson-style bolt, such as those from Kuehl Precision & Spikes Tactical
  •  AR-15 with .22LR-chambered barrels, with a .22LR bolt NOT based on the Atchisson adapter, such as those from Tactical Solutions



Rifles or dedicated uppers with .22LR-chambered barrels are far more accurate than "drop-in" .22LR adapters used with .223-chambered barrels. There are two reasons for this. One, the centerfire bore is supposed to have a nominal diameter of .224-inch, while the rimfire bore is supposed to have a nominal diameter of .221-inch. Those three thousandths of an inch do matter. Also, .223 barrels use a twist rate anywhere from one turn in 7 inches, to one turn in 12 inches. A .22LR bore has a twist of one turn in 16 inches. The too fast 7-inch to 12-inch twist, combined with the loose bore, means poor accuracy. To fill the .223 chamber, .22 rimfire conversions have a chamber-shaped extension. A smoothbore extension. So the bullet starts out skidding down a smooth bore, then slams into an overly large and too-fast twist bore.

Tactical Solutions .22LR AR-15:
Tactical Solutions manufactures the AR-15 .22LR Conversion unit as a complete upper receiver and .22LR-chambered barrel assembly. It will fit on any standard AR-15 Lower. The Unit is self-contained, and is not designed for full auto use. The AR-15 Conversion unit comes with one 25-round "Black Dog Machine LLC" magazine (10 round magazine available for California).

Three models to choose from:
  •   AR-15 M4: This option is similar to the standard military AR-15. It features an A1 Flash hider.
  •   AR-15 LT: This lightweight option features a threaded aluminum barrel and Hogue forend.
  •   AR-15 MC: This integrally suppressed conversion unit features a Mono-Core sound suppressor with removable titanium baffles for easy cleaning.