Lancer L5 AWM 30 round magazine. Here's my problem:

Loaded up brand new L5 mag (I load 25 rounds) and inserted into rifle with bolt locked back. Released bolt using the bolt release button. Failure to feed. Tried a few different rifles with the same result.

The bolt hardly moved the round at all. It moved the round forward about 1cm or so.

I have several older style lancer mags and did not have this problem. Upon closer inspection, I noticed that the finish on the feed lips of the new L5s is very rough, creating a lot of friction. I loaded and unleaded the magazine by hand until it started to wear down the finish a bit, and I noticed that he frictions was starting to subside. I then retried chambering a round and it worked flawlessly.

I then tried another brand new one from the same order, failure to feed with 25 round and bolt locked back. Repeated break in process, then it worked fine, just like the first one. It seems like they just need a break in period. Has anyone else had this same problem? Any other associated problems? Do you guys think the new L5s are as reliable as the old ones?

I have the translucent ones and never had a FTF. Sounds like you may have gotten a bad production batch.

Mine are the opaque black ones. Are yours the original design with the smaller steel inserts, or are they the new version? I have several of the older ones that function flawlessly. I wish I could still buy them, I really like the rubber floor plates. The new ones just don't feel like the same quality. Seems like the story of my life lately...

Are you using steel cased ammo?

Shouldn't matter. I shoot a lot of steel case ammo and haven't had feed problems with my Lancer mags.

No, I've not tried that yet. It was Lake City green tip. I have a few boxes of Wolf around tho, so I'll have to try that and see what happens.

Take the mag apart and reassemble. Sometimes springs are installed upside down.

Most new mags of any type can use some breaking-in before being reliable or even working at all. There's actually very little about guns that is 'turn-key'.

My new L5s in 30 and 20 round, black translucent and clear translucent have all worked fine.

 That's inconsistent with my observations, especially when dealing with properly manufactured mags and guns.

I didn't realize there were different versions of the L5's

I have 7 from 2 years ago, no issues, and 3 bought this year, no issues either.
mine were translucent smoke, if that matters...

I have three versions of the L5 30rd magazines, all translucent smoke, a pre production gen 1, production gen 1, and L5AWM.

My newest is a L5AWM I bought early last year 2014, I also have some 20rd translucent smoke mags.

All my mags don't have any problems even when brand new, on my all Colt carbine gas system carbines with M4 enhanced feed ramps (X4), a Colt with midlength gas system Rock Creek Barrels with M4 enhanced feed ramps, and a Colt USGI M16A2 (20" government profile barrel) without m4 feed ramps.

Plus I also tried it on my Steyr AUG A1 16" carbine bullpup with NATO conversion stock to accept M16 mags all mags worked fine.

I'm using mostly 55 gr Winchester 5.56 (white boxes), NATO SS109 62 gr, and some .223 Federal bulk 55 gr commercial ammo.

I had the same issues with steel cased, especially Wolf polymer coated not feeding the first few rounds.  One of the reasons I stick to brass.  It's not Lancer specific.

I seem to recall that when the L5AWMs first started to ship they had a batch that exhibited the same problem that you're experiencing.  Lancer determined that the steel feed lips had not been sufficiently deburred after stamping.

So no, Lancer magazines do not require "break in" as such and your magazines are anomalous.  Fortunately, yours seem to be easily fixed although an email to Lancer with photos might be appreciated by them.

FWIW, Lancer L5AWMs are my favorite magazines.

These are my favorite and go to mags, and I have never had this issue.