Have owned a Colt SP-1 without a FA since 1979 and while have never had it jam I have had my Bushmaster A2 HBAR jam on the range twice, in both instances the bolt did not go into full battery locking the lugs with enough force that the charging handle could not clear the jam, Luckily after a few bumps of the FA the bolt finally seated and I was able to then clear the chamber.

BTW when an AR15 jams like that you cannot open the receiver as the bolt body sits just back in the buttstock tube preventing the upper and lower receivers from tilting open.

Another member mentioned there is a cutout in the bolt body that could be coaxed fwd on a gun without a FA but my guess is that after firing a few magazines the metal could be hot enough to cause a burn .

Note that the two little holes in the bolt cutout are gas exhaust ports and provide a direct path to the rotating piston and its bore and my guess is that keeping fine sand out of there is probably a good idea.


On a side note another A1 improvement to the original AR15 design was the "Fence" surrounding the magazine release button which was added to prevent inadvertently dropping the magazine while the rifle was slung.

Bottom line while the dust cover and FA are probably not critical in a civilian sporting gun IMO for the few $'s they cost to add its better to have them and not need them then it is to need them and not have them .