How do I tell if a l1a1 is inch or metric.
The one I was looking at is a century  reciever and the rest is steyr I believe.

Rear sight-Inch folds and is fairly tall. Metric doesn't fold ans is fairly short.

Front sight-Metric is round post, Insh is blade on threaded post.

Safety-Metric is small round knob at the end, Inch has beefy area for your thumb.

Charging handle-Inch folds, most metric will be fixed knob.

Mag release-Inch is large affair that is actuated ont he left side, Metric is on right and you should be able to reach it with your trigger finger (if you are a righty).

Bolt catch-Inch usually doesn't have a last shot hold open (unless it's been replaced), Metric has a last shot hold open.

That should be enough to tell, as most Inch kits have been built on Metric receivers and use Metric mags.

HTH,

Tim

Thanks for the info.
From what I remember(and your description) this would be an inch.  But like you said It could have a metric reciever.
Is there any way to tell on the reciever?

Go to the link below and it will have pictures that show the difference. The main one for practical purposes (which mag type) is in the mag catch area.


http://www.centuryarms.com/receivers.htm

By the way, even though it says you can, don't count on using metric mags in an inch reciever, I understand that this usually does not work.

Mack