I am considering purchasing an M16A2. This is not my first NFA item, but it would be my first MG. I have a couple of questions:
• Are there any serial ranges or forging styles that I should be looking for? Any I should stay away from?
• Other than price, is there any advantage to going with a US Property marked lower versus a non-marked lower?
• Some guns I have seen have a government acceptance stamp on them. Is there likely to be a substantial decrease in value if the stamp gets rubbed off due to use? I intend to shoot the gun with some regularity, and while I will of course be careful, it’s not going to be a museum piece.
• Can a gun marked burst have an auto trigger such as a Geissele SSF installed, and vice versa?
• Will any modern upper with a full auto carrier work?
• Are there any must-have accessories that are recommended?
• Anything else I need to know?

I'm sure your set on a a2 m16 but prices are closer to a rdias, I think you will have way more options. I think colts are the only option for a2 lowers I have seen a few Olympic a2 lowers but there kinda iffy on transferring..

• Are there any serial ranges or forging styles that I should be looking for? Any I should stay away from?

Personally if buying a Colt M16A2 I would get one with the traditional A2 forging.  

There are A2 marked guns out there with A1 style forging (why pay A2 prices for an A1 forging) and there are guns out there with the later A3 style forging.   The A3 style forgings didn’t exist prior to 86 and somebody/somehow got Colt to remake existing A2s with post 86 A3 style forgings or invented a time machine.  

Nobody has publically acknowledged how this all transpired but a whole pile of those A3 modern forging /rollmarked A2s came out of the woodwork a year or two back.  There are Oly A3s out there as well that are papered as transferable, but the history on those is known as Oly publically remaned pre-86 transferables with post-86 receivers, migrating the serial numbers. (until the ATF told them to stop)

All of those modern forging guns (both Colt and Oly) are gray-area/jail-bait in my estimation.

• Other than price, is there any advantage to going with a US Property marked lower versus a non-marked lower?

None that I am aware of.  I personally wouldn’t want a US Prop marked gun as it begets the question of is it really .gov property.  Its not as much of an issue with post 68 manufactured guns since you don't have to worry about  stolen .gov property which may have been  registered during the 68 amnesty.   Usually the .gov property marked guns go for a premium because they are more desirable by collectors.  For me, the .gov prop marking just additional liability or questions about ownership, however I know many folks find those markings desirable.

• Some guns I have seen have a government acceptance stamp on them. Is there likely to be a substantial decrease in value if the stamp gets rubbed off due to use? I intend to shoot the gun with some regularity, and while I will of course be careful, it’s not going to be a museum piece.

I personally think the big value hit is going to come when you shoot it and its no longer NIB anymore, not when the little white star/eagle stamp rubs off.

• Can a gun marked burst have an auto trigger such as a Geissele SSF installed, and vice versa?

Yes, a burst marked gun can take a regular 0-1-A or a Geissele FCG.


• Will any modern upper with a full auto carrier work?

Yes any modern upper will work.  However there are caveats to take into consideration with a 30K lower receiver.

Its risky to run a 9MM upper on a valuable transferable lower receiver due to the potential for damage.   If you do run 9MM setup make sure you get somebody with a lot of experience to set it up properly so you don't bust a hammer or trigger pin and end up egging out one of the FCG holes. Special consideration need to be taken in terms of receiver extension depth in order to prevent damage to the LRBHO pocket due to bolt overtravel.    

Similar precautions need to be taken for a super shorty 5.56 upper with a screaming RPM.

If you do run a piston upper make sure you install a buffer tube that protects the receiver from carrier tilt, which can damage buffer tube threading if left unprotected.

• Are there any must-have accessories that are recommended?

I would add a suppressor.

• Anything else I need to know

Be careful if you decide to change stuff out to more modern variations.    Changing items like the triggerguard or LRBHO if not done properly can easily result in damage to the lower receiver.  If you do decide to change these parts, make sure you have the right tools to get these parts in and out properly and don’t go banging on it with a hammer and punch like most folks do.

If you change the buffer tube from an A2 fixed to a carbine style telestock, make sure its installed properly and the carrier gas key  has proper clearance and can't hit the top edge of the buffer tube ring which can result in a damaged and/or a cracked receiver.

jbntex pretty much answered your questions spot on.

Are you looking for a MG to shoot or a collectors piece?
If you want a collectors piece a M16A1 or A2 is a great MG. But if you want to shoot it and not worry about damaging the value I would recommend RDIAS which is the same price range as a M16A2, or you can pick up a non-colt RR for half the price.

I've seen several Colt guns that were rollmarked as A1 but were actually A2 lowers, and the seller was not savvy enough to price them accordingly.  I'd like to have one of those.

i chose an A2 US property marked because i always like to collect the rare guns...i also bought NIB.....i paid over todays market price for it....so they are more of a bargain now than they were 9 months ago

i first decided to purchase as a collector and not touch it....but have since decided WTF and plan to shoot it

ive seen them for sale with the mark wore off....didnt see a huge price difference if any at all.....you can buy that stamp somewhere or have it made you know and restamp it to sell it....that stamp may be fake also

i am keeping my upper & stock new.....i bought a 11.5" BCM upper for it and a M4 stock and grip.....im also changing out the trigger just to keep the colt parts in good condition....if i decide to sell it i can toss on the new parts and hopefully still have a nice looking/minty gun.......i will baby the lower to keep it looking nice....ive done it with all my guns......

for me id rather have a modern m4 style with a 11.5"  barrel....than a old school 20" barrel look....

with so many A2's for sale some sell cheap....find one for $27-28k......US Property marked doesnt seem to add any extra value lately....i have kept track of them and have 15 serial #'s in the past year....all from the same collection.....if your going to buy a New A2 now is the time for the best price

my a2 is dipped in grease....maybe 1/32 thick....going to have to clean the hell out of it to shoot it......i will most likely lose the white stamp.....i question if that stamp is real or not.....and dont care if my stamp comes off

JB, can you expound on this?

I saw an M16 where the buffer tube wouldn't come off. The gunsmith had apply heat and extreme torque to get it off.

also looking for info on this...ive owned a couple of AR/M4's but not  M16a2

i bought a bravo co tube and a T2 buffer

is your post more about the buffer?

how to check clearance?

My comment about changing buffer tubes is for somebody who may not be experienced on the platform and removes a standard A2 fixed stock receiver extension (aka buffer tube) and replaces it with a carbine style tube.

(Since that is how most folks want their M16s set up now-a-days and its a pretty straight forward amateur gunsmith procedure)

The issue is that not all buffers or buffer tubes are created equal and there is variation on how they can be installed.  The buffers themselves can also vary in overall length as well.

The A2 fixed stock buffer tube has a timing collar on it so you just screw it all the way down until it doesn't go any farther.   The carbine tube is threaded on and timed with the castle nut.  How many rotations you screw the buffer tube on before locking down the castle nut (and then staking it)  is up to the installer and the limits of the buffer retaining pin.

So you add up the fact that not all tubes or buffers are to spec, plus the variability of the installer and how deep they screw the buffer tube onto the receiver, and you can end up with the Carrier Gas Key making contact with the upper portion of the receiver extension ring during the recoil stroke.

When the rear of the gas key can make contact with the lower receiver buffer ring..... bad things can happen.  

You can leave a gas key indent in the lower like the pic below.



or worse crack the receiver.



Its easy to check to make sure you have proper clearance when installing a carbine buffer tube.

Remove the buffer tube spring, drop in the buffer, and then push the carrier all the way in.  Check to make sure you have a proper gap between the gas key and the receiver extension ring.

I am not aware of any official spec but I personally like to see a minimum of a 0.15" gap as the rubber bumper on the carrier will compress during the recoil stroke as well.  I like run more of a 3/16" (0.1875) gap in my guns.    You can get upwards of 1/4" gap depending upon the gun and buffer before the LRBHO wont be able to catch the carrier properly anymore and of course the ROF goes up a bit the less travel the BCG has.



Hope this helps.

thanks for the pics...its exactly what i needed to see

my A2 is about a month away and ive gotten the new upper all ready to go....

from the video's ive watched on replacing the old a2 buffer tube with a modern m4 tube i wouldnt think there was any option for a different depth...you screw it in so it barely holds the buffer retainer....if you were to over thread in the tube wouldnt it be over the top of the retainer and then the buffer would not stay in the tube?

my setup is all Bravo Co...so i assume they are smart enough to set me up with all the correct stuff....ive spent multiple emails with them to verify things.........you just scared me since i have so much $$ into this m16

i will check using your pics when i put it together

Well hell, I actually learned something new about ARs today; thanks for sharing that, JB!

If the parts are all in spec than yes the tube should just barely screw over the buffer retaining pin to retain it and the depth should be good.   Bravo company makes decent parts so the odds of stackup issues are low if you are using their tube and buffer.

However, it is a 2 minute check to make sure everything stacks up properly.  

Whether the receiver gets hit also can vary on the upper you are running.  You might have a gap on the smaller side (0.1")  that may befine with a standard mil-spec 14.5" M4 Colt upper that is softer recoiling.   Swap that upper out for a shorty 7.62x39 upper and the much more violent recoil stroke compress the rubber bumper on the buffer more than 0.1" gap you have and then you get the carrier key indent into your lower.

There are also a multitude of buffer tubes designed to "protect" the lower receiver buffer tube threads from carrier tilt on piston uppers or even hard recoiling DI uppers.  These tubes can have a much larger variation on how deep or shallow they can be installed due to the longer lower length of the tube and the fact that they are specifically designed to screw over the top of the buffer retaining pin, which then pokes through the tube.

Somebody buys one of these "enhanced" tubes below thinking they are doing a good thing for their $30K M16 receiver, then installs it like youtube says to install a normal tube (where the front lip just covers the buffer pin) and now the overall depth is much greater as tubes like these are designed to screw in much deeper than normal.  Next thing they know they have a serious dent in their lower receiver.

Very good info, thank you all!

Thanks, JB. You are a fountain of knowledge.

Thanks for the tutorial, jb!  I wish I'd seen it before I stripped and rebuilt my M16, but I used good quality parts and lucked out.  That still didn't keep me from running to my safe just now and checking it all the same .

OP, I was in your position last year and after a while of back-and-forth, decided on an M16A2.  The choice between that and a DIAS was a tough one, and in the end it's a very personal decision, and as much about what you really want the most as it is about any logic.


There was a thread awhile back (I looked for it just now without success) in which Tony_K posted about the joy of being able to own, as a civilian, a factory Colt machine gun; arguably one of the great small arms of all time.  That's what it's about for me.  In the end, for me, what I really wanted was an M16A2 with the "Auto" rollmark (as opposed to the "Burst"), and that's what I wound up with.  Makes me all warm and fuzzy every time I shoot it.  The DIAS might be more practical, but there's no way it would make me as happy.


Here's a thread that I could find, in which some members here with a lot more experience than I have, discuss this very thing:



Happy hunting!

If you do find yourself in a situation where your bolt carrier is going too deep into your buffer tube, a quarter makes a very quick and dirty "spacer" which will decrease the depth of the buffer tube if dropped in before inserting the spring/buffer.

Quarters work will if you need more gap in a pinch.

Ares actually supplies a "quarter like" spacer to install with their Shrike/MCR upper.

The Ares carrier doesn't have a gas key (being piston driver) but does have the actuator arm feed roller in a similar location on the carrier.  

Since the Ares feed roller actually comes back a touch with farther than a normal DI Carrier Key does and the Shrike/MCR is a more violently recoiling upper compared to a "normal" M4 or A2/A3 upper, Ares includes a quarter style spacer specifically to prevent the feed roller stud from hitting the buffer tube ring.

Anyone have experience with David Spiwak (www.davidspiwak.com)? Is he GTG? Any other dealers besides Reuben (doesn't currently have what I'm looking for) with a good reputation?

He's good to go. I haven't personally bought anything from him but he's got a good reputation.

I have chosen to stay away from David; two of my friends that I know well and trust have commented that they did not feel good about dealing with David.  David even described in detail to one of them how to misrepresent the condition and configuration of his machinegun so he could pass it off as a rarer NIB model M16 when he was ready to sell it and encouraged him to do so.  He was shocked a dealer would do this because it obviously caused him to call into question the authenticity of the purchase he was going to make from David.  I emphasize was going to make.  Many have claimed to have had positive interactions with David.  I, however, have read and heard enough accounts of his unprofessional, unethical and legally questionable dealings to choose not to do business with him.

he is lower priced always and his guns always sell.....from my limited experience of trying to buy a thompson from him he did not want to put much effort into it...i had asked for more and better pics....he seemed to be gone for 2-4 weeks a lot and could not take pics....then told me he owns a bad camera and thats why his pics look poor.....i think people just see 3 pics and pay full price w/o questioning things......me being a buyer who asks questions and wanted 20 pictures to see how many parts were original to the thompson and how many are not showed him i wasnt going to be his customer...and he kinda blew me off.....many have bought from him and had good luck...for me i would find someone else.......Reuben is always expensive, but e mail him and notice you get a return 1 hour later.....if you dont mind spending $3-4k more his service is top notch........most also have a good experience with him

for me id just find one on GB.......thats where ive bought most of mine......from my experience most auctions end behind the scenes    (all of mine did)

find a M16 that didnt sell after a few times listed...contact him and make an offer (reasonable offer)....and youve got a decent chance of winning....dont pick a M16 that has a reserve of $10k more than its worth...just find one with a buyer who has a realistic view of what it is worth.....there are MANY who think they have Gold....GB is full of guns that have been there listed for 2 months+....some ive seen for a year....Dreamers

He is good to buy from. See the below list for rough prices and dealers.


Transferable M16 machine guns and estimated market values:
RLL $15-18k
RDIAS $27-32k
RR Non-Colt Cast AR15 Conversion $17-19k
RR Non-Colt AR15 Conversion $18-20k
RR Colt AR15 SP1 Conversion $18-20k
RR Colt AR15 614 $22-24k
RR Colt M16 $22-24k
RR Colt M16A1 $24-28k
RR Colt M16A2 $28-33k
RR Colt M16A2 Commando $33-38k (Marked "Auto" instead of "Burst")


Websites to watch for good deals on machine guns:
http://www.sturmgewehr.com
http://www.atfmachinegun.com
http://www.autoweapons.com
http://www.impactguns.com
http://www.subguns.com
http://www.onlythebestfirearms.com
http://www.davidspiwak.com
http://dealernfa.com
http://www.gunbroker.com
http://www.nfasales.com
http://www.classiiidealers.com/
http://www.westernfirearms.com/
http://www.collectorsfirearms.com/class-iii-full-auto/
http://www.urban-armory.com/
http://www.ar15.com/forums/f_7/118_NFA_Firearms_andamp__Parts.html

Website that tracks machine gun values:
http://www.machinegunpriceguide.com/

I have done 2 transactions with david s., hes good. But dealers are in it for the $$.

I have dealt with several dealers and several individuals as a buyer and a seller.  I have been burned on purchases from two dealers and four or five other dealers have been just fine both buying and selling; and I have not had any issues with individuals.

If you decide to purchase from a dealer, any dealer, treat the transaction pretty much as if your were buying from an individual.  That is, ask all the questions, request all the pictures showing details you want to see, request pictures of Form 3 or 4 copy showing that they are the current owner, video of gun being fired with a current newspaper in the video, etc. - whatever you need to feel comfortable.  If what you ask for is reasonable and the seller balks, move on.   Expect to pay more for a firearm bought from the dealer, but do not expect to get anything more than you would from an individual; but also demand that you get no less than you would from an individual.  Hope for the best, but prepare for the worst.

Best of luck with your experience and the firearm that you acquire.

MHO, YMMV, etc.

My .02c
Don't be in such a hurry that you settle for something that's not exactly what you want.
Other than the various MAC's, there are probably more transferable M16 type firearms in the registry than any other type so you should be able to find exactly what you want rather quickly.
Like others have mentioned, M16A2's come in many different flavors. Decide which is best for you. Look closely. A lot of people try and sell carbines that have "BURST" marked lowers and I would be suspect that those left the factory as full length rifles and were converted at a later date. Either because the previous owner liked the short configuration better or to get more from it when selling. From an investment standpoint, the highest value would be in a A2 marked carbine with a true A2 forging that is marked "AUTO" not "BURST".
As far as upper interchangeability, unless you are set on some of the more unique, modern styles, just stick with factory Colt parts. With a little patience, you can find any configuration of Colt upper and barrel length you want. And if you buy a full length rifle and want to convert it to a collapsible lower, to avoid any problems or possible damage to your valuable lower, again, just spend the little bit extra $$ and use original Colt parts. That way you are practically guaranteed a proper fit and function. I personally wouldn't risk my 30k lower by using an aftermarket receiver extension or bolt carrier group.
IMO, nothing inspires as much pride as owning a true, Colt factory made, select fire M16 of whatever configuration.

I have an opportunity to purchase an A2 burst-marked rifle with serial 80000xx. Based on the stickied post in this forum on serial numbers, it sounds like A2s started with the 8 million serial range. Does a sub-100 serial number mean that it's a very early gun? If so, does that have any effect on its value, quality, durability, or anything else? Tony_k, feel free to weigh in!

My A2 is in the lower end of the serial numbers and I have not really noticed anything different about it over the ones I carried in the Military.

Is the one you are looking at, through a private owner or a dealer?

Mine is a rifle and I have no intention of changing the configuration on it, it is a lower serial number.  Kind of beat up a bit, but still fully functional.

i remember a guy who had Steyr Aug #69 asking $500 more for it

a low # can be a big deal, depends on the gun....with Thompsons it would be (since they made millions).....there's a guy with GI Uzi #2 or #3 on Uzi talk....not sure if he paid extra for it, but claims it was owned by one of the manufacturers family which seems likely

ive found with a few guns that the quality is extra special on lower serial #'s and they cheap out the longer the gun is made....I have a low serial # DSA STG58......it has Steyr parts in it and is worth more than later serial #'s

i have the lowest serial # A2 govt marked out of the 15 i have seen for sale this year(by 100,000+)....do i think its worth more? nope

my guess its all in the eye of the beholder.....sell it and ask a $1000-2000 premium and see if a millionaire is willing to toss extra out to say he has a low serial #

if yours was 8,000,069 i may give you $1,000 extra for it!!!!

i do like unusual versions of guns and also low serial#'s....but ive never paid extra for a low serial #

i never cared about serial numbers. i look for good clean minty guns, and enjoy them. not hide them away forever.