I carried the C1A1 for 18 years. Also competed with it for about 10 years.
I've also owned and extensively fired both the M-14 and M305.
C1A1:
Good balance, better sights capable of finer adjustment. In well serviced condition the rifle can shoot better than most users. Straight line stock and pistol grip give good control during rapid fire. Pistol grip allows a good range of trigger contact but is not as "natural" as an orthodox rifle stock and good trigger control can be difficult for some people, especially those with hams for hands.
Magazines are very rugged and reliable but not invunerable to abuse like opening several cases worth of non twist top beers. All the same, hard to damage in normal operating conditions (As a side comment, the pockets of the old combat uniform shirt could be used to carry 6 magazines, although no one ever actually did as doing so was no good for doing anything other than perhaps walking slowly for a short distance.
Pockets were far better suited to carrying packs of regular size smokes, a note pad etc).
Reliable, but not utterly so. You can run out of gas adjustments and the regulator will foul up until almost frozen if sufficiently dirty. A tool to turn the regulator and scrape the carbon off it and the gas plug is provided in the cleaning kit if no one lost it last time out. Completely cleaning the regulator itself requires knocking out the gas tube pin and unscrewing the locking bolt which connects it to the receiver so the regulator can be removed. Not a quick job for the user in the field. Carry handle was a plus, usually for hooking it into the frame of a 64 pattern ruck for the long hikes (like trotting all over Cornwallis island, loaded up like a pack mule), otherwise not often used as rifle was either slung in the field or being used for arms drill in garrison. Was handy for carrying 4 or 5 back to the arsenal. Freqently became loose and would rattle about, get caught on gear etc.
Locking shoulder needs replacement from time to time. Axis pin can become worn/loose as can the locking lever. Fore end halves held on by one screw which can be lost. You can gun tape them on until it gets hot but it's not much of a fix. Same with breaking the handguard halves. Hump on the stock behind the rear sight beats up the cheek bone nicely.
Field stripping is easy but leads to a pile of parts such as breech block, carrier, body cover, gas plug, piston, piston spring etc.
When well maintained, the C1A1 was more than adequate for it's purpose.
M14/M305
Dirt simple to strip. Less parts to loose. Almost impossible to shut down except with defective ammo. Sights not as fine as the C1 but still very useful. Off the rack M14 or M305 shoots as well as any similar condition C1. Magazine not as rugged and more easily damaged. In it's day they were probably considered semi disposable. Mag latching does not provide as positive a lock as C1. A damaged operating rod spring guide will prevent proper mag instalation as will a damaged slot on the front of the mag. More of the magazine is also exposed on the M14. Orthodox rifle stock is better suited for long range shots (for me, anyway). Likewise, it allows a more "natural" (for me, in any event) feel for the trigger and is deep enough to accomodate a fair range of hand types. Stock to rifle bedding is superior to the C1 and there is no flex between upper and lower receiver or loose handguards to be concerned with. Gas system requires little user maint but again, is not invunerable to filth. Having said that, it will take more crap than the C1 before quitting.
C1 bayonet was good for a wide variety of uses and made an excellent all purpose tool for opening ammo crates, cans etc. About as sharp as a nerf ball so carry a pocket knife. M14 bayonet is nice and pointy and is also sharp. Having never pig stuck an enemy (or friend, for that matter) I cannot attest to the usefulness of the C1 bayonet for that purpose. In my opinion the M14 bayonet would be a nasty bit of work in the belly but you will go hungry or have to live on John Wayne cookies if you haven't got your trusty p38 can opener. Likewise, have a pry bay around for ammo crates and the like as the dainty profile of the M6 bayonet is not up to the task.
I'm sure others will have much more to say. These observations are just some quick and dirty stuff off the top of my head. I am not a weapons tech, weapons designer, or veteran mercenary nor do I play one on TV.
:wink: