The L86's biggest problem was that it had been overtaken by technology. In the past, British sections had used the Bren gun as a light machine-gun. This worked well in a day when the average soldier had a bolt-action rifle. When the British went from the Lee-Enfield bolt-actions rifles to L1A1 semi-automatic rifle, they also adopted the the L7 General Purpose Machine Gun.
Later, when the infantry switched from the L1A1 to the L85, the United Kingdom wanted to switch to a light machine-gun that used the same 5.56-millimeter round. The L86 was intended to do this, but it was not really much different than the L85 rifle (with over 80 percent commonality of parts). This was a problem. Whereas 30 rounds had been sufficient for a Bren gun, it just didn't hack it for the modern world when compared to the M249/FN Minimi (which had 200 rounds of 5.56-millimeter NATO).
This is not the first time that weapons have come to take on very different roles from their original design. Two of the most famous World War II fighters, the P-47 Thunderbolt, and the F4F Wildcat, started out looking very different than the forms that became famous in that war. The P-47 started as a lightweight fighter that was intended to serve as an interceptor with two .50-caliber machine guns. The P-47 instead turned into arguably the best ground-attack plane of that war - and was probably the first definitive fighter-bomber, armed with eight .50-caliber machine guns and the ability to carry 2,000 pounds of bombs and as many as ten five-inch rockets.
The Grumman F4F started out as a biplane, losing in a Navy competition to the Brewster F2A Buffalo before it was modified and became the primary fighter for the United States Navy from 1941-1943, and serving throughout the war, becoming famous as the aircraft flown by aces like Joseph Foss, Butch O'Hare, and James Thach.
Will the L86 work out as a "designated marksman" rifle? It's not quite known. The concept has been picked up by the United States, which uses a variant of the M16 for this role. The Marine Corps uses a version of the M14. As such, this rifle has a chance to work out - if it can overcome the prejudice caused by its earlier failures. - Harold C. Hutchison (firstname.lastname@example.org)
While the British Army's acquisition of the FN Minimi (which served as the basis of the M249 Squad Automatic Weapon) seems to indicate that they have given up on the L86 as an automatic rifle, it has not meant failure. On the contrary, the L86 is still expected to stay in service, as a "designated marksman rifle". This is an effort to make something out of a system that failed in its initial role (drawing comparisons to the French Chauchat machine gun that plagued French and American soldiers in world War I). But it also is not the first time that a weapon system became something far from what it was intended to be.