The Army will soon be replacing the M4 Rifle and the M249 Squad Automatic Weapon.

With the awarding of a ten-year, $20.4 million contract to Sig Sauer, the XM5 Rifle and the XM250 Automatic Rifle will become the new standard small arms weapons for soldiers.

Soldiers will also switch from using 5.56mm to 6.8mm ammunition after a search for rounds better suited for penetrating body armor.

"Both weapons fire common 6.8mm ammunition utilizing government provided projectiles and vendor-designed cartridges," an Army spokesperson said in a press release.

"The new ammunition includes multiple types of tactical and training rounds that increase accuracy and are more lethal against emerging threats than both the 5.56mm and 7.62mm ammunition."

The Army's decision to replace the M4 and M249 arrives after a 27-month long evaluation process in which other defense contractors, including General Dynamics, competed to become the service's small arms dealer of choice.

Both weapons provide significant capability improvements in accuracy, range and overall lethality. They are lightweight, fire more lethal ammunition, mitigate recoil, provide improved barrel performance, and include integrated muzzle sound and flash reduction.

The XM5 and XM250 will also come with a XM157 Fire Control optic, that includes a laser range finder, ballistic calculator, visible and infrared lasers, and a compass. The new optic is produced by Vortex Optics.

It is not clear how many of the new weapons the Army will purchase over the decade, nor is it clear how long it will take to field them.  In its proposed 2023 budget, however, the Army requested 29,046 of the arms. That budget is still waiting Congressional approval.

U.S. Army release contributed to this story.