AI mag feed lip adjustment

[Apnea]

Summary of what I have learned:

308 magazines can feed 6.5 Creedmoor, but metal mags don't always do a good job without some feed lip modification. I understand from Adam at Mile High that this is because the 6.5 case taper is a little different than 308. When pushing the bolt forward to chamber the cartridge, the cartridge tends to go straight forward instead of assuming the desired nose-up posture that will send is smoothly into the chamber.

On plastic magazines, the lips bend a little bit and allow the cartridge to feed without modifying the lips. Given the reputation AI magazines have for flawless reliability in dirty conditions, i wanted to get them to run rather than rely on plastic magazines.

There are inexpensive tools made for modifying feed lips (MDT makes one). You could also improvise, but you don't want to tear the lips up with regular pliers. I happened to have some flat-James Vise Grips that seemed made for this.

I measured the factory magazine feed lip gap at:
Rear; mid; front
0.397; 0.390; 0.337
And after a few times gently bending outward (pliers provide lots of leverage), I tried feeding again, with considerably improved bolt effort and cartridge behavior. I re-measured the feed lip gap at:
0.423; 0.413; 0.400.

I'll leave them here and run it at the range next time I go, but it feels good running 6.5 snap caps at home (snap caps are about 8 thousandths narrower than my 6.5 Prime cases, so more tweaking might be necessary.

 

[Apnea]

 

[spife7980]

I need to do this already. I just use my plastic magpul now as they ran flawlessly from day one. Pains me each time I leave that pricey metal hunk of junk on the shelf each time.

 

[whatsupdoc]

I have been using the sheet metal vice grips to bend mag lips, only difference is I use some electrical tape on the jaws not to mar the feed lips.

Works great.

 

[308 pilot]

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Any suggestions for tuning AW double stack mags?

 

[Holliday]

I used one of these for .308 feeding issues with great success: https://masterpiecearms.com/shop/mpa-mag-feed-lip-adjustment-tool/

 

[wrpicket]

Any suggestions for tuning AW double stack mags?

Did you ever figure anything specifically out on this question?

I used an MPA feed lip tool to open mine up, mostly in the front, as the cartridges we going in too straight initially and then tended to push to the opposite side crashing into the chamber edge and jamming. Once I opened them up enough I was able to get the cartridge to line up a little straighter, but not much, but it releases before it crashes and seems to feed okay.

Just wondering if anyone has good measurements to start with or an optimal width to begin with. My tweaking came out a bit asymmetric since it was test and tune via Mark-1 Eyeball and is triggering my OCD, Lol.
But at least it worked.

 

[greentick]

Interested to see if there are some "starting point" measurements.

I just tuned 3 AWs for my Impact/Bravo build with a Brownells tool I had for my ARs. I just went slow and used the Mk1 eyeball as well. Seemed like they fed somewhat asymmetric to begin with so I wasn't too stressed. I did the majority of adjusting with a couple of snap caps and then checked with 11rds as well. As with many things repetitive, by time I was tweaking the third mag, it went pretty quick.

 

[JS/]

I used an MPA tool and opened the lips to .405-.410 or so. Looking at the rear with a cartridge in place, I make sure the primer is above the rear edge of the mag. Feeding in an Impact 737R has been great, and the MPA Comp chassis has been super. This is for regular aics magazines.