Just one month into its official existence, a program to replace the Army’s M4 carbine with a 7.62 mm rifle has been canceled, Army Times has confirmed.

First reported Thursday by The Firearm Blog, the Interim Combat Service Rifle had been in development since at least this spring and was officially announced in August when the Army sought industry samples to produce up to 50,000 rifles.

The rifle would have replaced the M4, a variant of the M16, which has been in service for half a century and fires the 5.56 mm round.

Critics claim the round does not have the distance or lethality needed for modern small unit tactics, especially after upgraded body armor has been shown to be able to defeat the 5.56 mm round.

Most soldiers and Marines carry 5.56 mm M4s, M16s or M27s. Marksmen, snipers and machine gunners fire the 7.62 mm round or a round of similar size.

The Army is working on an intermediate caliber round and rifle combination that would fall between 5.56 mm and 7.62 mm, giving soldiers greater range than their current weapon and greater power and penetration.

Army officials have noted that the rifle-in-progress will replace the M4 and M16 family of weapons. But the Interim Combat Service Rifle was expected to fill that firepower gap while the more long-term program progressed.

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Army officials did not provide an official statement on short notice when contacted late Thursday afternoon for comment.

This story will be updated as more information becomes available.