Originally Posted By SteelonSteel:
yep, handguards

you'd have to swap for an inch lower to use inch butts and grips.

the metric has a whole different trigger set up with a stirrup affair for trigger return while the brit has the trigger return pin and spring mounted in the grip itself. Also the brit style has a bushing like an inverted top hat pressed/rollled rivet style to the lower that the grip pops over. A bolt is passed from the inside of the lower to engage a threaded bushing pressed into the wood or plastic grip. The metric lower has a long threaded rod attached to the lower instead of the passed through bolt.

Also the buttstock sockets are completely different. you can swap Aussie and Brit and I think Indian. The very early canadians were metric style but later I do believe went with the brit style socket.

Should be a doable trade if you posted over on FALFiles. Post that you want to trade inch lower for metric. I think the only issue is the argentine recievers sometimes want only an argentine lower but if yours is argentine with a brit lower on it you're likely already clearanced for the swap. Just ask over there as there is a metric tonne more FAL knowledge there than I have.

BTW Does your inch lower already have a wood stock on it? I'm on the look out for an English S marked walnut buttstock. The S ones are short length.