Looking to buy my first AR15/M16 style MG (the M10/45 is fun, but I need a M16/AR15 before its too late).

When talking machine guns, why is the M16 ~8-10k more than a M16/AR15 conversion? Also can someone explain to me what a converted full auto is? Are they just semi auto AR's that were converted to full and documented as so before 1986?

Lastly, while looking around it seems to be well known that the Sendra and SGW are a good bit cheaper, almost half the price of a Colt M16, but haven't seen any reason why, just people telling other people that's the "cheapest"...

You are right on track.  

Some are cheaper due to the quality of the work (either perceived or actual).  As long as the holes are not egged out, (or drilled out of spec) it is just a name game.   Of course a factory colt M16 will bring a premium, but it is a collector premium that is unimportant to most shooters.

PS, as far as "converted" this could be anything from a properly converted receiver with a proper sear to a normal semi AR with a "Drop in auto sear" our other hillbilly conversion which is advertised creatively.....  look for the 3rd pin hole if that is important to you....

FPNI

I've owned a few M16/equivalents.  So long as the lower is in spec to start with and the holes properly aligned and not egged there is little difference functionally.

I had an original M16 Colt.  I also have an SP1 conversion.  Could not tell much difference using them except I needed the large hole adapter for the SP1.  Both would accept any upper etc.

I kept the SP1 as I wanted at least one MG.  If I might interject, the one I wish I kept was my MP5.  I was the most fun to shoot and the most fun to let neophytes shoot.

How exactly would you check if it were in spec? I've owned dozens of Ar's over the years but none I ever really checked, I just threw an upper on a lower and went shootin'!

I assume testing a few uppers would test the fit of the 2 takedown pins, but without removing the trigger group how exactly would you check those and others?

Thanks for the answers

Topic Moved

Not really sure how you would check.  That's one reason Colt's get more than the lesser known conversions.

If I were a first time M16 buyer I think I'd go to subguns.com and check out their recommended dealers list and see what they have and perhaps buy through/from them.  Those dealers value their reputation and if they have it in stock they will have checked the holes for egging and that the upper they are selling it with fits.  Some might even do a firing function check.''

I really have no better ideas.  I've bought 5 NFA full autos of various types and never had an issue yet.  Doesn't mean it can't happen.

Best of luck.

At a high level there are three types of M16s out there.

Factory Colt M16s.  These are M16 that came from the Colt Hartford Factory as M16s.   These are going to be rollmarked Colt M16 (A1, A2).

These command the highest receiver prices specifically because 99% of them are "in-spec", they have the Colt Pony logo on them, and came from a qualified military manufacturer.  (The 1% that are not in spec have been damaged and repaired, modified, etc.)

The next class of guns are the AR15 conversion.  The bulk of these guns are made by SGW (precursor to Olympic Arms), Sendra, Essential Arms, and Colt "SP1" guns.

The SGWs are notorious for having a slightly high top deck which makes upper fitment an issue.   The Sendra are usually anodized a "purple-ish" color and there are reports of metallurgical issues.  Essential Arms guns are cast (not forged) and have a pretty rough appearance.   The Colt SP1 conversion are missing the mag release fence and require the use of a front takedown "conversion" pin to use normal mil-spec uppers.

On top of that the quality of the conversion work ranged from Joe-Bob with a hand drill and dremel to work almost indistinguishable from factory.

The reason the conversion guns are less expensive is because of this variability and the potential that you may have a bunch of work to get them up to spec.

(see my post on an SGW I just recently brought up to spec and which took multiple shipments and  $1000+ in work & parts)

http://www.ar15.com/forums/t_6_23/477923_How-to-choose-an-AR15-M16----.html

The last option are registered sears (DIAS and RLL).  These drop in conversion sears will convert a standard AR15 to a machinegun but do require additional parts, timing adjustments, and some level of mechanical intervention by the end user so the AR15 properly functions on full auto and you don't damage the conversion part if its set up improperly.  These run $35 to $15K depending upon the sear.

If you want a gun that is going to be idiot proof/plug-in-play than just buy a factory Colt M16.

If you want to save $5000 to $10,000 you can go with a conversion gun but you will need to do more due-diligence on the sale and ultimately be prepared to spend $1000 getting it to spec. This could require milling, shimming/bushings, anodizing, etc.

If you want to build a gun around a registered sear you will need some level of mechanical ability or be prepared to send it off to somebody who can build and set up a gun around a sear for you.

There are a bunch of other nuances I didn't go into (Group SS, Colt 614s, married sear guns, etc.)  that can be researched on this site.

If you ever have a gun you have a question about, post it here and folks will give you plenty of opinions before you plunk down a bunch of cash.

edit

Great response, that should get my gears turning for now.. thanks!!

I can add this, Sendras are overrated.  I have seen nearly as many fitment issues with them as Olympic lowers.  If I had known this, I would have bought a sweet Olympic for $9500 back in 2010 or 2011 instead of waiting for that better Sendra to appear which never happened.

Bring a Colt or LMT upper if you want to test out the fit of a lower.

My Sendra has been good so far and every upper I've tried has fit fine on it.

My Olympic was out of spec and had to have the top deck Milled down and also sanded down a bunch of forging marks the factory over looked. A couple weeks and a few hundred dollars later and it was in spec, looks brand new with a fresh layer of anodizing and I saved $5-10k by not buying a colt.

Most importantly I love that I can treat it like a real gun, I take it to the range, roll around in the mud, bang it against other gear and it doesn't matter short of breaking it in half it won't hurt the value as no one cares if there are scratches on and non-colt RR, but even the littlest if scraps of dents on a colt can hurt the value.

I have a Sendra. Never had a single functional issue. I did have two uppers that were a little tight on the rear lug. After using them a few times they both worked fine. I wanted a Colt too, but I knew Sendra's were normally properly converted lowers and the next cheapest Colt was the 614 for 4k more.
If you watch prices of registered MG's the cheaper ones tend to rise the fastest. I don't think a Sendra will ever be worth as much as a factory Colt, but probably not too far off one day (from the 614 not the A2).

Not to hijack. This threads is great...

but what is "egging" and what holes am I looking at?

Egging is damage to the fire control pin holes in the lower receiver..  More often than not the hammer pin and to a lesser degree the trigger pin.

This is caused by running the lower with excessive recoil force and/or a broken pin.

This results in the former perfectly round pin hole taking on an oval shape that resembles an "egg".

The fix is to weld up the hole and redrill it or drill out the hole and put in a bushing to restore the original round hole.