Excerpt from this Ruger Guide:
The Mini-14
At first glance the Mini-14 looks very similar to a combination
of a M1 Garand Rifle’s rotating bolt and the overall appearance of
the US Military M14. The M1 Garand (.30.-06 caliber) was adopted by the
US Army in 1932 and was carried by most US troops until the 1950’s. The
M14 (.308 caliber) was adopted by the US Army in 1957 and was later
replaced by the current AR-15/M-16 rifle. (.223 / 5.65mm caliber).
Design and Series of the
Mini-14
The Ruger Mini-14 was designed by Bill
Ruger. Early versions from 1972 ~ 1975 were produced in Southport,
Connecticut and have serial numbers with the three digit prefix of
“180”.
The Ruger Mini-14 180 series have a
few minor internal and external design changes that make it incompatible
with most of the commercial and aftermarket accessories that are
specifically made for the later 181 and 182 series rifles.
These early 180 series rifles are
sought after by collectors.
Most “shooters” prefer the later
models.
The Ruger Mini-14 series 181 was
introduced in 1977 and offered an updated rear site, a larger gas
piston, magazine release, and a modified bolt mechanism. In 1980 Ruger
added a series 182 which introduced a new satin finish to the Mini-14.
Early stainless steel receivers were recalled due to cracking because of
excessive hardening of the metal during production. Recalled stainless
guns had a serial number below 182-51929. Ruger Rifles that have been
repaired have two proof marks. (“R” in circle.)
