The U.S. Army is considering several upgrades to the M4A1 Carbine that could improve its accuracy and performance and change the weapon's appearance.

Army weapons and contracting officials recently launched a market survey to see what the small-arms industry has to offer as far as better rails, triggers, charging handles and sights for the M4A1.

"The government is seeking to procure M4A1-Plus (abbreviated as M4A1+) components as non-development items ... for improvements to the M4A1 Carbine," according to the March 13 document posted on FedBizOpps.gov. "It is anticipated that the M4A1+ components will be evaluated as a system. The system must then install on/interface with stock M4A1 Carbines."

The Army decided to replace the standard M4 with the M4A1 in 2013 after the service abandoned a five-year effort to replace the M4 with a brand-new carbine.

The M4A1 is the special operations version of the M4 that's been in use for more than a decade. It features a heavier barrel and a full-auto trigger. The Army's decision to dump the current three-round burst trigger resulted in a more consistent trigger pull and better accuracy, weapons officials said.

The selection of the M4A1 came out of the service's M4 Product Improvement Program, which looked at improvements such as an improved rail, trigger pull, bolt and bolt-carrier group.

The M4A1+ effort will look for add-on components that will "seamlessly integrate with the current M4A1 Carbine ... without negatively impacting or affecting the performance or operation of the M4A1 weapon," the document states.

All M4A1+ components will need to be compatible with current M4A1 ancillary equipment such as optics, aiming/pointing devices, training devices, slings and rail covers.

One of the upgrades is an improved extended forward rail that will "provide for a hand guard allowing for a free-floated barrel" for improved accuracy, according to the document.

The improved rail will also have to include a low-profile gas block that could spell the end of the M16/M4 design's traditional gas block and triangular fixed front sight.

The effort also calls for new, removable front and rear back-up iron sights that attach to the rails and "stow down/away to reduce interference with the mounted primary sights and flip up to enable soldiers to engage targets out to 300 meters," according to the document.

The sight apertures should provide for both near threat to 200 meters to longer, 300-meter engagements and allow for windage and elevation adjustments out to 600 meters without degrading threshold capabilities.

The improved rail system for the M4A1+ will also feature a Coyote tan or "neutral (non-black) color" for "reduced visual detection," the document states.

"The color range will be Coyote 498 not lighter than Light Coyote 481," it states.

The M4A1+ would also feature a more effective flash suppressor/muzzle brake brake "designed to reduce the day and night firing signature and night vision device blooming effect of the weapon to be less than the current carbine without loss in system performance," according to the document.

An improved charging handle would provide shooters with an enhanced grasping surface area with an "extended latch capability for improved hand/finger-grasping access and enhanced operating leverage/operation for both left- and right-handed shooters." the document states.

The M4A1+ would also include an enhanced, single-stage trigger module "free of creep with consistent trigger pull weight within the range of 4.0 to 5.0 pounds," according to the document.

Companies interested in participating have until April 3 to respond.

-- Matthew Cox can be reached at Matthew.Cox@military.com.