9MM Poly-Mag Modification?

Discussions on the Pistol Caliber AR15

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9MM Poly-Mag Modification?

Postby 9milshooter » Wed Sep 07, 2016 8:02 am

I snared a couple of AR 9-mil Poly Magazines off an auction site for a real good price. They were advertised as 10-rounders and were so stamped. I've never taken them apart, but obviously a previous owner had. They function flawlessly and were never used that much. The OLY verbiage indicates these mags were "permanently" fixed at 10-rounds. I think I am the owner of a couple of 10-rounders that have been de-modified to 30-rounders by removal of the limiter plug. I can't say that makes me mad either. :D 30's are not banned where I live, so I suppose I'm not illegal either. I also suppose I could go in and modify them back to 10's if I needed to.
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Re: 9MM Poly-Mag Modification?

Postby Globemaster » Wed Sep 07, 2016 4:22 pm

very nice! :thumbs up:
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Re: 9MM Poly-Mag Modification?

Postby Rattler » Thu Sep 08, 2016 8:04 am

The poly mags are made from glass embedded polymer. They are really tough and can actually be machined. Taking a 10 round magazine and returning it to high capacity is possible, but it does require some machine work. Anytime machine work is required, the item has a level of "permanency" as defined by BATF. Like a flash suppressor 'permanently' installed in the end of a 14.5" barrel to make it a legal 16" in over all length. To be legal, it has to be permanently attached, pinned and welded. But, if machined, it can be removed.

The way the mags are blocked is by inserting plastic plugs/blocks that are then epoxied in place. the try and just pop them out, or pry them out will likely damage the mag body itself, then rendering the magazine inert. But by machining the blocks/plugs out, one could likely return a 10 round magazine to high capacity (with the appropriate springs as well).

Hope that helps.
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