AR57 Magazines

[reckless1911]

I just completed my 5.7 build and realized that I simply messed up and didn't read the fine print on the CMMG site that their 5.7 conversion mags only work with their proprietary upper receiver which they don't sell stripped (of course) and only as complete. So basically the mags don't lock in with the bolt closed, but lock in with it open and soon as its released it hits the mag before catching the bullet to feed into the chamber. If I hold the mag to the standard position to where it should be it feeds and ejects no problem so I'm assuming CMMG just decided to engineer the mags to need you to spend 1k on their uppers that only have some kind of lip that stops the mags from going up into the mag well further than they should lol. I was going to take the gun to my gunsmith and see if there was an was solution that could be fabricated so that I can utilize the CMMG mags that I already have, but I was also wondering if there are any other 5.7 AR mags or drum available that would also work?

 

[smdub]

Modify the mag catch notch?
Could glue a rib on the mag to prevent it from going up too far.

Edit: and I'm not aware of anyone other than CMMG that makes 5.7 AR compatible mags.

 

[reckless1911]

Modify the mag catch notch?
Could glue a rib on the mag to prevent it from going up too far.

Edit: and I'm not aware of anyone other than CMMG that makes 5.7 AR compatible mags.

where could i get the material?

what about this drum?

https://palmettostatearmory.com/promag-magazine-5-7x28mm-55-round-drum-fits-ar-style-fn-5-7-polymer-black.html

 

[jrumann59]

3-D Print a rib that could be glued/epoxied in place.

 

[Worsley]

I’d buy the non-stripped upper and sell the other parts.

 

[smdub]

Does the empty CMMG mag lock in and clear the bolt on an AR15 upper?

The CMMG upper is RDB which is basically identical to a 5.56 AR15. I wonder if the 5.7 bolt you are using is the real culprit. Is is blowback? Whose upper parts are you using?

 

[reckless1911]

Does the empty CMMG mag lock in and clear the bolt on an AR15 upper?

The CMMG upper is RDB which is basically identical to a 5.56 AR15. I wonder if the 5.7 bolt you are using is the real culprit. Is is blowback? Whose upper parts are you using?

im actually using the CMMG bolt also. I wonder if the issue is with the mad catch. Will have to get it to the gunsmith

 

[smdub]

Do you have a different lower/gun to try it on? Any regular AR15.

 

[reckless1911]

Do you have a different lower/gun to try it on? Any regular AR15.

Yup.. exactly what I just did. Tried the CMMG mags on 2 of my other 556 and 300blk ARs and they clicked in perfectly to where it would feed fine if the bolt was 5.7 and then I tried my other 556 and 300blk mags in the 5.7 and they wouldn’t click in like the CMMG didn’t so the problem is with the mag catch on the lower not being extended enough to catch the mag, I can actually see how recessed it is. I take responsibility for all of this because I didn’t include one of the mags when I dropped the parts off at the shop and they even said they couldn’t test it out because of that but let them know if anything is off.