Here's some very good info on Mini's put together by BWRaven on this site. There is a lot of good info on best bullet weight for each barrel twist on here as well. I have a 183 and found the strut and a Hogue stock really helped the accuracy. After these mods it shoots as good as my new heavy barrel 582.
180 Series Mini-14
Beginning
Serial Nbr
180-00001--1974--1 in 10
180-05101--1975--1 in 10
180-28282--1976--1 in 10
180-59251--1977--1 in 10
Mini-14
Thin barrel, ejector is in the bolt, no scope ring scallops cast into the receiver.
Beginning
Serial Nbr
181-07488--1978--1 in 10
181-48351--1979--1 in 10
181-84879--1980--1 in 10
182-45601--1981--1 in 10
183-03581--1982--1 in 10
183-40455--1983--1 in 10
184-17175--1984--1 in 10
184-26063--1985--1 in 10
184-95448--1986--1 in 10 and 1 in 7
185-14140--1987--1 in 7
185-50455--1988--1 in 7
185-56556--1989--1 in 7
185-81009--1990--1 in 7
186-05029--1991--1 in 7
186-18250--1992--1 in 7
186-20065--1993--1 in 7
186-31116--1994--1 in 7
186-42502--1995--1 in 7
186-58133--1996--1 in 7
186-66855--1997--1 in 7 and 1 in 9
186-81445--1998--1 in 9
186-87432--1999--1 in 9
*196-06325-2000--1 in 9
*196-44553-2001--1 in 9
*196-80982-2002--1 in 9
*196-99207-2003--1 in 9
*197-12180-2004--1 in 9
* Mini-14 serial numbers rollmarked with Mini-14 Ranch Rifles beginning in 2000
Ranch Rifle
Thin barrel, ejector in the bolt stop assembly, scope ring scallops cast into the receiver, buffer sytem using the recoil spring assembly.
Beginning
Serial Nbr
187-00001--1982--1 in 10
187-02611--1983--1 in 10
187-13218--1984--1 in 10
187-27226--1985--1 in 10
187-50919--1986--1 in 10 and 1 in 7
187-59308--1987--1 in 7
187-70033--1988--1 in 7
187-84127--1989--1 in 7
188-01157--1990--1 in 7
188-30499--1991--1 in 7
188-50902--1992--1 in 7
188-66901--1993--1 in 7
188-71086--1994--1 in 7
188-85981--1995--1 in 7
195-06037--1996--1 in 7
195-27761--1997--1 in 7 and 1 in 9
195-44221--1998--1 in 9
195-63542--1999--1 in 9
196-06325--2000--1 in 9
196-44553--2001--1 in 9
196-80982--2002--1 in 9
196-99207--2003--1 in 9
197-12180--2004--1 in 9
New Mini-14 Ranch Rifle
580 Ranch Rifle (early version): Thin barrel, ejector in the bolt stop assembly, scope ring scallops cast into the receiver, buffer sytem using the recoil spring assembly, new tooling resulting in a slightly different look to the receiver (more rounded edges, etc.)
580 Ranch Rifle (later version)-581: Thicker flanged barrel, ejector in the bolt stop assembly, scope ring scallops cast into the receiver, buffer sytem using the recoil spring assembly, new tooling resulting in a slightly different look to the receiver (more rounded edges, etc.)
Beginning
Serial Nbr
580-00001--2005--1 in 9
580-15286--2006--1 in 9
580-32382--2007--1 in 9
580-50951--2008--1 in 9
* 580-76276
and 581-00000--2009--1 in 9
* 581-48753--2010--1 in 9
* 581-71056--2011--1 in 9
* 581-95645--2012--1 in 9
* New Mini-14 Ranch Rifles rollmarked with Mini Thirty Rifles beginning in 2009.
Mini-30
Beginning
Serial Nbr
186-00501--1986--1 in 10
189-00001--1987--1 in 10
189-15143--1988--1 in 10
189-17652--1989--1 in 10
189-25005--1990--1 in 10
189-38805--1991--1 in 10
189-51041--1992--1 in 10
189-52528--1993--1 in 10
189-59348--1994--1 in 10
189-65480--1995--1 in 10
189-75697--1996--1 in 10
189-82126--1997--1 in 10
189-84971--1998--1 in 10
189-89313--1999--1 in 10
189-96162--2000--1 in 10
*196-06325-2001--1 in 10
*196-44553-2002--1 in 10
*196-99207-2003--1 in 10
*197-12180-2004--1 in 10
* Mini Thirty serial numbers rollmarked with Mini-14 Ranch Rifles beginning in 2001
New Mini-30
Beginning
Serial Nbr
581-01002--2006--1 in 10
581-05892--2007--1 in 10
581-06747--2008--1 in 10
581-11910--2009--1 in 10
581-48753--2010--1 in 10
581-71056--2011--1 in 10
581-95645--2012--1 in 10