Last round feeding issue with Okay Surefeed 20s

[CharlesAFerg]

That's a good point.
In a straight-tube 20rd USGI, the follower HAS TO TILT upward in order to present the rounds at the correct angle to feed.
If someone has "upgraded" the correct 20rd followers to an "anti-tilt" follower, the last few rds. would take on a "nose down" angle.
The mag feed lips could be bent....another thing to check.

The 20rd USGI mag, the original M16 mag, is considered by many to be the Gold Standard mag for these rifles.

These were brand new in packaging. The black one I shot was the first time it was ever used.

 

[CharlesAFerg]

I would not rule out the possibility something is off in the rifle. A stack up of tolerances maybe affecting only one type of magazine. Except its odd it doesnt happen to his 30 round magazines of the same make.

Well, they have magpul followers. Probably different enough to negate any issues the 20s have? Idk

 

[Koda]

interesting ar15.com discussion on surefeed 20s and someone having issues with them not fitting some of their lowers. Measured the surefeed mag to GI spec he says his was oversized.

Anyways, its a rabbit hole to go down but my only guess right now is a stackup of tolerances. If you have a tight lower and a fat surfeed 20 it could maybe constrict the follower in the wrong spot on the last shot...

Who has Okay Industries 20s still in stock? - AR15.COM

Firearm Discussion and Resources from AR-15, AK-47, Handguns and more! Buy, Sell, and Trade your Firearms and Gear.

www.ar15.com

 

[DirectDrive]

Well, they have magpul followers. Probably different enough to negate any issues the 20s have? Idk

The wrong type of follower (for a straight 20) would look like this :


The right kind of follower (for a straight 20) would look like this :

 

[CharlesAFerg]

The wrong type of follower (for a straight 20) would look like this :
View attachment 1492661

The right kind of follower (for a straight 20) would look like this :
View attachment 1492662

The question was never whether I had the wrong follower. I know that the followers are correct on these mags. These were brand new mags in their packaging and have the correct followers. The magpul followers are in some my 30s, not my 20s. Some of the 30s have blue followers but that's not an issue. None of my 30s are problematic.

 

[DirectDrive]

The question was never whether I had the wrong follower. I know that the followers are correct on these mags. These were brand new mags in their packaging and have the correct followers. The magpul followers are in some my 30s, not my 20s. Some of the 30s have blue followers but that's not an issue. None of my 30s are problematic.

This information ^^^ was not in you post #1, therefore I mentioned it not knowing if these were new mags, used mags, rebuilt mags etc.

 

[CharlesAFerg]

This information ^^^ was not in you post #1, therefore I mentioned it not knowing if these were new mags, used mags, rebuilt mags etc.

We were talking about my 30s, and you didn't reply to the first post. This is a thread...

 

[DirectDrive]

We were talking about my 30s, and you didn't reply to the first post. This is a thread...

I saw Surefeed 20's in the first post as the problem mags.
I guess I missed the 30rd conversation.

 

[Oro]

Late to the convo but this may be helpful.

Bottom line first: Last round feeding issues are almost always spring-strength related or feed-lip related. And I HAVE heard of, but not experienced, this issue (at arfcom) with those mags.

I am a 20rd fan and have used them almost exclusively for decades. I have run everything from 1st gen AF contract (the "Circle 1" mags) to relatively recent (c.2010) OK/NHTMG mags, and everything in-between (Colt, Adventure Line, Simmonds/UI, Parsons, etc.). That said I don't hold myself as the ultimate expert; I'll share what I know. Most of what I really learned about mag function was building/tuning 1911s, but it translates really well from my experience. It is actually a metric cr&p-ton easier in the AR than the 1911 or other handguns. Here are some bullet points:

• I have heard of this issue w/Surefeed at Arfcom. The poster solved it by hand-dressing the feed lips, which were burred. This was a convo about 18 months/two years ago, IIRC.
• This makes a lot of physical sense, because the demands on the spring are maximum at the last round. Any additional drag can cause a ftf. TOO LITTLE drag can also be an issue, but that is not generally an AR issue. This is because feed lip shape in AR mags is almost universally consistent, whereas in 1911s it is allover the map (do not get me started on this, lol). AR feedlips either provide the correct amount of tension, or too much.
• In the '60s, it was common to load only 18 rds in the GI mags of the time, as last-round FTF were common. I wasn't in Viet Nam so that's not 1st hand knowledge. But I've heard it from enough combat and non-combat vets to believe it. This issue has been around a long time. My gut feeling is it was because of worn-out springs and no maintenance - which is an educated guess but not definitive.
• Try dressing the feed lips, and if you have other well-functioning 20s, swapping in the springs from them as a test.
• By dressing the feedlips, I mean taking a fine jewelers file (round works great here) and lightly working over all edges of the lips and the contact surface underneath.

Take a fresh look at your problem with the above info added. If it still persists, then consider this:

I may have some new extra 20 rd springs in the parts box(es). I know I have some new 30s. I'll poke around in the garage tomorrow and if you do NOT have other functioning 20s to spring-swap, AND the feed-lips are butter smooth, AND I have some, I'll send you one or two different new 20rd springs to try. Again, not sure if I have any extra new 20 springs or not but I might.

 

[monkeybutler]

This is surprising given that surefeed mags were favored by the hardcore AR gear heads. Not sure if they still are because I stopped paying attention, since I can't buy any more standard capacity mags at this point.