The M21 rifle is a rifle based on the M14 rifle and was the primary Army sniper rifle for the Vietnam War till it got replaced by the bolt action M24 Sniper Weapon system in 1988. The M21 accuracy is about 750 yards and uses the US match grade M118 NATO 7.62 cartridges in five-round or 20-round magazines. With the immense accuracy, the M21 can fire at long-range ball and ball/tracer and armor piercing ammunition. Its long-range ammunition produces stringent tolerances to ensure superior accuracy.
It is the ultimate rifle that has auto-loading accuracy and in active duty, is has elite spec-ops groups world-wide. The M21 is classified as the ultimate tool for those entire law enforcement sharpshooters. The rifle is equipped with an adjustable cheekpiece stock, which enables it to maintain its perfect head alignment with the scope. Known for being accurate, reliable and powerful, the M21 rifle remains the world class standard for sustained precision fire.
On the other hand we have the M1A. In a nutshell, the M1A is a high-quality reproduction of the U.S. M14 rifle which was used in the early years of the Vietnam War. First is was criticized as being outdated but with its re-introduction in 1957, the M1A remains in service today with certain U.S. Army, Navy, and Marine units as well as other law enforcement units around the world. The Springfield M1A capitalizes on the popularity of the M14 type by using GI parts and specs.
This rifle is gas operated and comes in a military style configuration. The Standard model of the M1A costs around $1000 when purchased on an online auction site and it is classified as an assault weapon if equipped with a pistol grip or flash suppressor in several states.
The obvious differences between the M21 and the M1A are the M1A has a vertical recoil system whereas the M21 can move to the left or right while firing. The M14 holds more bullets, but more damage is done by the M21. Also, the M1A is a semi-automatic/automatic rifle while the M21 is a modified version of the M14 which is especially built for sniper activity.