M14 to Armalite AR-10 Mag Conversion project

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15 years 2 months ago - 14 years 9 months ago #2036 by crux
M14 to Armalite AR-10 Mag Conversion project was created by crux
Note: I will be editing this post as I fill it in with completion of the project. About half way through now, stay tuned.

Intro

Mostly for my own amusement and to test my skills, I've been wanting to try and document the conversion of the M14 mag to an AR-10 mag. I've seen some notes but have never seen a good solid guide, so I'm going to try and document the major steps for reference. Obviously this conversion can only be performed in places where it is lawful to do so, and the reader is responsible for understanding their local laws. I live in a rather progressive state where no one cares what you do with your mag.

Now I know Armalite at one time offered conversion kits, but no longer does, so I'm going to try a conversion without the benefit of any Armalite parts.

I picked up a cheapo M14 30 round mag at a gunshow on a whim. I had heard that they could be converted for AR-10 use, and while I definitely prefer the size of the Armalite Gen II 20 rounder, the technical challenge of making a 30 round M14 mag work with the AR-10 was hard to pass up. I also enjoy confused stares, and figured a 30 round mag hanging out of an AR-10 should get some. Ultimately the answer to "why" is "because I can" (or more correctly, to see if I can) and "gotta have a hobby."

Here is the monster side-by-side with a Gen II 20 Round mag.

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Comparisons

It's obvious here the AR-10 mag was designed from the M14 mag. Armalite had some lousy luck with the timing of Clinton's AWB. This M14 basis was chosen so that it would be possible to have hicap AR-10 mags via conversion. I worry that this will be an eventual problem for Armalite now that the Knights has been selected for the M110, and DPMS is compatable with that mag while Armalite is not. But I digress...

Here's the back of each side by side.

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The fronts. Notice the hole on the M14 mag where it rocks into the rifle.

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Top views

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Side showing the Mag Catch hole on the AR-10 Mag

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Here's the biggest differences. The M14 mag just has a block where the mag locks into the rifle. Armalite Gen II has a channel all the way down that the Bolt Hold Open tang rides in. The M14 mag grip block will have to be cut down some, and the follower will have to be modified to pop out a tang for the Armalite BHO to catch on.

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Planning the Cuts

There's probably a fancy way to measure and mark the places to cut. I just went with my old grade school trick of folding paper and making marks on it with the pencil to copy the distances. In both designs there is a crease at the top of the mag where it curves to hold the next round, I measured down from there.

Here's the mark for the Mag Catch hole.

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And for the channel in the back. That locking block is going to be interesting to cut through with just my poor cordless dremel.

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Dissasembly

Need to get the follower out of the way for the cutting, so I'm taking the mag apart. Used a screw driver to pull the bottom of the mag off. Really cheap mag here, the floor plate bent quite easily. You get what you pay for (which wasn't much).

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Here it is completely disassembled, follower out the bottom.

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Modifications - The Mag Body Cuts

Now it's dremel time. Cutting away the mag release hole and the channel in the back.

Here it is half way through. My cordless dremel needs a recharge frequently. New battery needed for Christmas. You'll want to do this some place where you don't mind getting filings of steel all over. Eye protection is a good plan as well.

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Here it is with the finished cuts

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Test fit. Locks into place fine, a little wobbly but stays put.

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Looks a bit ridiculous from the outside doesn't it.

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To the depth I've cut, it looks like there's very little room for something to pop out and catch the bolt hold on the way up. May need to cut down further.

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Modifications - The Follower
This is where everything went horribly wrong :ohmy:


The key with the follower is that you'll need something to pop out as it clears the M14 mag body to lift the BHO lever. In the following picture you can see the Armalite GEN II mag on the left, and the notch in the follower that the BHO comes to rest on. On the right you see Armalite's GEN I mag, which has a little tab that pops out as it clears the mag.

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I couldn't find any GEN I followers, so I came up with an idea to mount a pin and spring under the follower of the M14 mag. Unfortunately, here's where "Cheap" comes back to bite you in the behind. As I mentioned earlier, this mag was CHEAP, $14 dollars. This was evident when I tried to remove the floor plate and it warped. That's a clear sign right there that you're going to quickly exceed the design limits if you get too creative.

To be frank, the follower was too flimsy to handle the modifications and I made a mess of it. The tang under it that meets the spring popped right off, and I don't have any welding abilities so I've had to give up on a GEN I type follower for now.

This of course means I have two options, put a block that stops the follower as it comes up to feed the last round, and not allow it to go further, allowing the bolt to close on last round (Which is what I'm used to with my AK anyway), or just let the bolt bang into the follower on last round. Not desireable.

I'll post the picture of the result here.

So I took the follower from the backup mag I purchased, and just installed it in the mag body for now.

Reassembly

Just drop the follower back in the mag, feed the spring back in, and push the floor plate back into place.

M1A compatibility
During the AWB it was necessary that the M14 mag still work in the original arm. Let's test it on an M1A.

Problem is I'm still waiting for a my buddy with the M1A to meet me at the range!

Pics and Video to come.
Last edit: 14 years 9 months ago by crux.
The following user(s) said Thank You: mlotziii, mini14gb

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15 years 1 month ago #2096 by BUILDING MY SASS
Replied by BUILDING MY SASS on topic Re:M14 to Armalite AR-10 Mag Conversion project
Hey Crux, how is it going on the testing, man you have more ingenuity than I have the patience for. I remember reading how the earlier AR-10 mags where modded M-14 mags and that if you had to, you could use a standard M-14 Mag and tape it or hold it in to operate. Anyway, just was wondering how the experiment was going.
Keep us posted on the progress...........
BMS

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15 years 1 month ago #2098 by zfk55
Replied by zfk55 on topic Re:M14 to Armalite AR-10 Mag Conversion project
We have quite a few AR10 Mags here, but unfortunately...... none of them work for the new rifle.
Its chambered and throated to fit one projectile profile and we found out why the seat depth is critical. Even though the standard AR10 mags will go in, they're .020 short to allow for the Sierra 175gr MKs seated to the required depth, and I mean required. The 4 magazines supplied with the Wilson are actually .020 longer overall to accommodate that seat depth.
I'd never heard of that but it is what it is, and it would be no small project to lengthen the entire magazine.

zfk55

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15 years 1 month ago #2100 by crux
Replied by crux on topic Re:M14 to Armalite AR-10 Mag Conversion project
So far it works fine EXCEPT I'm still pondering a cheap easy way to do the bolt hold open. Sure I could get all fancy and have someone weld up some custom bit of machining, but I'm trying to think minimalist here. Can I make a BHO pin driven by a ball point pen spring or something of that sort, trying to avoid anything that needs fancy machine tools.

One difficulty is that the follower seen in pic 10 has a flange for the spring, and it's quite in the way of the hole I'll need for the BHO to go through. I could hack it all off and rework the spring, but I'm trying to think of something that can be done that doesn't mess with it.

I certainly can't blame Armalite for moving on to Gen 2 as quickly as possible :)

That said, I could always stop the follower at the last round allowing the bolt to close over it after it's ejected (i.e. keep the floor plate from rising up to get whacked by the bolt). I doubt hitting the follower is going to bother the bolt, but it's just not how it's designed to operate and I want to avoid off-nominal operation.

Honestly what I think would work best for the BHO is some sort of mini-deadlatch like you have on a door knob. Haven't seen any but that would work perfectly. Probably going to grab a length of metal rod from Home Depot and file it to the same profle, and build up something for the spring to drive it along as the follower clears the mag notch.

Work doesn't permit enough time to experiment for the moment. Likely to drag on into next month. I'm pleased it works and could feed the 30 rounds, but I won't be happy till I have it working fully.

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15 years 1 month ago #2101 by crux
Replied by crux on topic Re:M14 to Armalite AR-10 Mag Conversion project
zfk55 wrote:

We have quite a few AR10 Mags here, but unfortunately...... none of them work for the new rifle.
zfk55


I'm not clear, which rifle? I'm interested but having a hard time visualizing the problem. Is the top of the mag from it's anchor point too short, thereby delivering the round too low?

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15 years 1 month ago #2102 by zfk55
Replied by zfk55 on topic Re:M14 to Armalite AR-10 Mag Conversion project
This one.

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The Receiver began as a standard Armalite but the builder altered the magazine well. The barrel is a dedicated barrel to the Sierra MK175, chambered and throated for just that projectile and no other profile, seated to a specific OAL. That OAL is slightly longer than an AR10 standard magazine, thus the custom made magazines.

zfk55

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13 years 5 months ago - 13 years 5 months ago #7577 by crux
Replied by crux on topic Re: M14 to Armalite AR-10 Mag Conversion project
New development!
Armalite is selling post ban state compliant 20 round mags for $25 each:
www.armalite.com/ItemForm.aspx?item=EX05...37-a759-b2d36557d12d

Now someone in a ban state will probably hate me for this, but these mags appear to have the gen I followers I was having trouble recreating. Just ordered a pair to see if they can be used to finish the project properly. Hopefully photos to follow soon.
Last edit: 13 years 5 months ago by crux.

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13 years 5 months ago #7586 by BUILDING MY SASS
Replied by BUILDING MY SASS on topic Re: M14 to Armalite AR-10 Mag Conversion project
ANTICIPATION.....ANTICIPATION.......Glad to see you made an appearance... :dry: :laugh: ;) :woohoo:
Will wait with...well... :laugh:
Good to see you on again....
Later.
BMS

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13 years 5 months ago #7704 by edritchey
Replied by edritchey on topic Re: M14 to Armalite AR-10 Mag Conversion project
CRUX - I think I know what might work for your conversion... I'll PM you with my idea to think about. Like you I love this type of project.

EDR

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12 years 1 month ago #12485 by Spook
Replied by Spook on topic Re: M14 to Armalite AR-10 Mag Conversion project
:) Thank you for taking your time and trouble to share your project...I have in the past simply cut the square hole in the side of a M14 mag and as long as it was cut right, it seems to work and feed in both my Springfield M14 and My AR10T...the problem was getting the hole just right...your method of measureing and cutting I havent tried but now that I have a router table with small metal cutting bit, I plan to make a jig just for the mags...I only have Gen1 so they dont seem to be so complex...Just had to try something being IMHO the Armalite mags are priced way to high...And as always, where theirs a will, theres a way...Thanks Again!! and good shooting.

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