AR-180 Mags and Catches


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AmEngRifles
August 24, 2010, 04:42 PM
Just been doing a little reviewing of my AR-180s and came up with an interesting discovery. I know I had some issues with different mags working in select versions of my 180s. The Sterling didn't like to take some of the earlier, unmarked steel 30 rounders. I finally figured out why!

It really isn't a big deal, as I have a number of modified magazines from earlier days. I did them myself, and some of the earliest ones are a bit rough. I became much better at the conversion and those actually look semi-professional. It all has to do with proper slot placement and length.

Some of these early Armalite steel 30 rounders have what I would describe as very "short" mag catch slots. It wasn't a problem as long as I was using those mags in a Costa Mesa or Howa produced 180s. But I could never quite grasp why the Sterling would not lock a mag in place??

The idea hit me to flip the rifles over and compare the mag catch tabs. Guess what!? There IS a difference. See photo below. The Costa Mesa and Howa have a very similar mag tab locations. BUT, the Sterling for some reason has the tab in a somewhat different location. See the image with mag wells all lined up and notice how the Sterling mag tab is forward more so than the other two. Not by a lot, but enough to cause an issue with these Costa Mesa supplied magazines from an earlier time. The slot in those mags are very short. Although early 20 round aluminums have the longer slot for some reason! These longer slots are used throughout Sterlings manufacture of the AR-180 steel and aluminum magazines. The "longer" slot is even used on Thermolds or Wilson 180 mags (see picture)

So now I know the answer. While I hate to alter an early original 30 round mag, I think I will elongate the engagement slot. It is just too bothersome to have to remember, "yeah, this mag works in this rifle, but not THIS rifle", and so on. Since the slot is already positioned in the correct height, on the vertical plan, it is only a matter of elongating the slot a bit with a little filing. Most people would not even notice, and I feel it is better to have compatibility across the board. So a heads up for you Armalite fans if you ever run into a problem.

By the way, look at the attached image with the Wilson/Thermold AR-180 mag. I now realize there are two drag marks. The AR-180 is notorious for leaving these. They show up especially fast on the soft, aluminum, black anodized 20s that Sterling used to supply with their 180s. It is showing me that after inserting this mag into the various made 180s, I have my proof about slot differences right there! There are two distinct drag locations corresponding with the tab locations between the Sterling and the other two makes. Just wonder why Sterling changed their product in this manor?

Off to fix the 30s!

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