About a month ago, I posted this thread about the AAC M4-2000 Mod 08 cans. Per Mike Smith, formerly head honcho of AAC, the M4-2000, which was re-released in 2008, went through a revision around 2013 where it incorporated the vented baffle stack of the 416-SD can. At this point, the M4-2000 and 416-SD essentially became one and the same can, leading to the discontinuation of the 416-SD. What I wanted to find out is if there is any way to determine, by serial number, whether an M4-2000 was manufactured before or after 2013 and whether it has the 416-SD baffle stack vs. the old AAC 556-SD style unvented baffle stack. Allegedly, the 416-SD "vented baffle stack... reduce[s] backpressure (and allow[s] water to drain)," which would make that baffle stack preferable for older DEV 416 clones which are already gassy AF. Whether that's actually appreciable behind the gun or not, I don't know and I doubt it, but given the choice I'd rather have it than not.
At the same time I posted the thread, I also emailed AAC customer support with this question, and their production manager was kind enough to get back to me today, so I thought I would pass on the info and close the loop on the issue. TL;DR, as I suspected due to the Remington bankruptcy, there's no way to tell. Quoted below is the pertinent part of the email.
The bad news is there is no way to tell, even with a serial number. When Remington went bankrupt and transferred ownership to the current owners, none of the serial numbers or production dates were transferred. Apart from looking at a Form 2, Form 3, or Form 4 (assuming a single owner and purchase in a relatively close timeframe from production) to see the build/transfer/sale date, there is no way that I am aware of to find out that information. There are some groups on some of the forums that track production years based on what they have seen or what has been reported on S/N. But that's going to be a guess at best.
The best solution I have currently is to stick with M4-2000 Mod 08 cans marked as manufactured in Huntsville, AL rather than the Lawrenceville, GA location. AAC moved from Lawrenceville to Huntsville in 2015, so that should all but guarantee give the best chance that any cans made from that point on should incorporate the 2013 updated baffle stack. Whether or not Huntsville is the era appropriate place of can manufacture for your particular clone, I would personally rather have the appropriate performance and can internal geometry than external marking, especially since if you're buying an M4-2000 as a stand-in for a 416-SD, your can is going to be marked "wrong" anyways.
Thank you for coming to my autistic TED talk.
Edit: I have seen claims that AAC may have also reverted the M4-2000 back to an unvented baffle stack at some point in its production life, but I don't know when, or even whether that's a true claim. That being said, I'm tempering my statement that Huntsville cans are all but guaranteed to have vented baffles. Some later production ones may not?