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DIY Short AR-style Magazines for Ruger American Rifles

14K views 14 replies 8 participants last post by  GTidewater 
#1 · (Edited)
Hi all, I've seen a few threads on here looking for smaller or flush-fit magazines for the American series with AR-pattern magwells. I've posted some photos of the modified Magpul Pmags I put together and had some interest in how exactly those work. So, here's an overview of how to make some yourself.

Before I started chopping up Pmags, I tried a few of the commercially available smaller mags.

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From L-R, the Magnetospeed 3-rd, Brownells 5-rd with the spacer removed, and a Promag. Followers on the last 3 all replaced with Magpul anti-tilt followers. Still, none of these worked very well, mostly with feeding issues.

So, knowing that Pmags have a good reputation for reliability, are cheap, easy to cut and also have thick enough walls to hold together when cut / notched, I figured that was my best bet.

A few caveats:
  • I've only worked with a 5.56 Ranch rifle and 10-rd, 223/5.56 Magpul Pmags. I'm guessing things will be pretty similar for other calibers / other polymer magazines, but no guarantees.
  • This is by no means a professional product, and I'm no expert craftsman. This is just a fun project I put together in the basement with whatever I had lying around at the time. With any luck, someone else will figure out how to do this better and let us all know.
The first step is the simplest: cut off the bottom of your magazine. Where exactly depends on what you want the capacity to be and also how much you want to shorten the anti-tilt follower. Here are the measurements of the two I’ve made, as well as how they look in the Boyds’ AR magwell and the original Ruger part. The shorter one holds 3 rounds and sits mostly flush (in the Boyds), the larger one holds 5. You can cut flat or at an angle if you prefer the way that looks.

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Next, make some cuts, level with each-other, at the front and rear of the magazine body, slightly above the bottom. These are for inserting the new floorplate as well as supporting it. They should be at least 5mm above the bottom of the mag body for strength.

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You’ll also need to cut notches into the internal ribs on the sides of the magazine body, to allow the floorplate to slide in and to prevent it from bending under pressure. I did this by taking the blade off my hacksaw and running it through the cuts at each end.

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For the new floorplate, I traced the mag on sheet metal and snipped out the outline. You'll end up trimming this down a bit, especially the sides, until you can slide it in through the rear cut and all the way forward. Once you've got it the right size, drill a hole in the middle.
It should be a tight fit, I sometimes use pliers to start pushing it in and then a screwdriver pressed into the hole in the middle to slide it along.

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Make sure it’s wide enough to rest on the rib notches, but not so wide that it pushes the walls outwards. If you notice the magazine is hard to insert/remove later, you might need to trim it some more.

If you don’t have any sheet metal around, I think anything thin and semi-rigid would work here.

Putting the second half of the instructions in another post because there's an attachments-per-post limit.
 
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#2 · (Edited)
Alright, here's the rest.

Once you have all your cuts made and are able to insert and remove the new floorplate, it’s time to modify the follower, spring, and what I’ll call the spring-bottom, the polymer part attached to the other end of the spring. Not sure what the real term for that is.

Cut the spring from the bottom, to retain the bends where it attaches to the follower. For the 5-rd magazine I cut the spring roughly in half, and for the 3-rd I took a few more loops off. Here are those both compared with an original 10-rd spring.

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Here I also cut down the “legs” of the follower, and cut the magazine-bottom almost flat. This isn’t strictly necessary, but you can fit in more rounds in a smaller magazine this way. I’d recommend testing as you go here, put the mag together, see how many dummy cartridges or empty cases you can fit in, and then remove a bit more material if needed.

Unrelated, but just a note: if you wanted to file down the top of the follower to a softer angle to allow the bolt to close on an empty magazine, this would be a good time to do so. I skipped it.

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You’ll also want to cut a groove in the front of the spring-bottom, so it won’t be blocked by the rib that runs up the front of the mag body.

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At this point you’re functionally done. You can push the follower/spring/spring-bottom into the mag body, and slide the new floorplate in to keep it there. The mag will work, and swap between your Ruger and an AR fine.

However, I wanted to put the original floorplate back on, mostly for looks. If you don’t care about AR compatibility or ever disassembling the mag again, you could go ahead and glue it on. Since our new floorplate is handling the spring pressure, it doesn’t need to be very strong. If, like me, you want to keep it in place but easily removable, drill a small hole in the spring-bottom to match the one in the new floorplate. Then you can run a screw into the polymer from below to hold the original floorplate on. To make the screw sit flush, carve out the sides of the hole in the original floorplate a little bit.

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And there you have it. I’ve put maybe 50 rounds through each of these with no issues.

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If anyone makes these, let me know. Would love to hear how it goes and if you find any shortcuts or alternative ways to do it.
 
#5 ·
Thank you for posting this. I wanted a shorter mag for my 6.5 grendel ranch but all I could find was the standard metal mags. Not only does the magpul work but is quieter. I went by your instructions with the exception of the base plate. I used the original and drilled holes through the mag and used pins to hold the oem plate in. I used drill bits for pins. I then slid the bottom cover over the plate and used a screw to hold it on. Works great. I used the 5 round pattern but didn't take in to consideration the size of the grendel cartridge being bigger than the 223. Mine holds 4 rounds but that's fine with me. Thanks again.
 
#6 · (Edited)
Great stuff. I have been looking for one of those Magnetospeed MiniMags and came across your thread. Hadn't seen many problems reported with the MiniMag until this. I am trying to find or make a magazine that allows handy carry at the balance point of a Fightlite SCR.



Its funky angled mag well adds to the challenge, and that's why I think the extremely low profile of the MiniMag is the best solution. Do you think cutting the bottom of the PMAG at an angle like many small AR mags have?

 
#7 ·
Hey HTT, You could cut the bottom to whatever angle you like, as long as there's enough mag body left to support the internal floorplate. I'm not sure how many rounds you'll be able to fit if you're going for flush-fit though, that magwell looks super short. The smaller of the two I made just holds 3 rounds, and I think it would still stick out a bit from the SCR.
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#9 ·
The ~40mm is end of the feed lips to bottom of the true mag body, with "foot" removed.

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Keep in mind that's just where I cut it, it's not an exact requirement or anything.

I also think I could probably shave enough off the follower to fit a 4th round in there.
 
#12 ·
For me, it's about handiness and carrying the rifle at the balance point, which is about where the magazine sticks out of the action. Box magazines are good, but not when it comes to carrying the rifle in one hand. When you need to carry in one hand, it's important. Of course that is not all the time. Box magazines are also good because you can carry a 30 rounder should the need arise. Generally though, 1-3 rounds is plenty.
 
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