New Rebuild from M-16 parts

Status
Not open for further replies.
loose noose

loose noose

Member
Joined
Feb 22, 2012
Messages
3,456
Location
Southern Nevada
A friend brought me a "rebuild for a M-4 from a variety of M-16 parts", naturally the gas piston is too long, as is the fore end, he brought me a standard 16" barrel chrome lined, and the front sight for the original M-16, which won't fit over the 16" barrel. On the lower he provided a safety switch for the m-16 which rotates all the way from safety to full auto, on a Spikes Tactical receiver. Half of the parts for the lower receiver just wouldn't fit, and I had to get into my parts drawer just to get the lower receiver assembled so it would shoot on my Bushmaster upper in the semi auto mode. By the time he buys the parts for the upper, he would have been further ahead to just go ahead and buy the completed m-4 carbine, in DPMS, Bushmaster, etc.

Anybody else here have such a parts gun to assemble, note the upper receiver is supposedly from a Colt M-16? If so tell me how did it come out?:what:
 
Come on now folks over 140 views and no one out there has ever had the misfortune of putting such a firearm together. I'm still waiting for the gas block/front sight for a m-4 from Mid South, then I'll be able to take it out and see if it shoots before I return it to my buddy. The thing is with buddies like that who needs enemies.:banghead:
 
Second for AR-15.com.

Problem with milsurp parts is that they were designed to go together as a unit--military M-16's have went through several iterations with subtle changes and different contractors. A grab bag of parts from a gun show or even places like Sarco will mix up parts made by numerous contractors with differing tolerances in one big lot.

From my limited experience based on milsurp bolt rifles and reading about milsurp gunsmithing challenges in the Shotgun News and the like for semi-auto conversions, you will probably have to handfit parts and even replace some parts before you are finished (for example, Colt changed the pin diameters on later military rifles). Just look at the reviews of conversions of military automatics converted to semi by sellers such as Century International, IO, etc. Some work great while others have all sorts of gremlins due to part mismatching. You might want to grab a copy of the Shotgun News compilation on Gunsmithing Projects--it does have several articles on the AR-15 including using surplus parts.

My hobby is restoring bolt action milsurps and even there parts bin/mismatched parts can give you fits in feeding, bolt operation, barrel fitting, stock fitting etc. At times, I spend a lot of time with files, rasps, etc., and then polishing and refinishing. Occasionally I have to more workable parts to replace ones that simply don't play well with the other parts. I can remember a M1917 safety block that gave me problems until I fitted it. A Springfield 1903a3 would not feed well with the milled 1903 follower (experienced 1903 people feel free to snicker here). When I replaced it with the cheap looking stamped steel version as issued, all was well.

Partly because of that reason and because of lesser scarcity, parts rifles generally bring lower prices because reliablity may be compromised. I do it because I'm a shooter, not collector, and I have the time to keep plugging away at it until it works well. I also have the satisfaction similar to rescuing animals from the pound of rescuing mangy military mutts. It also allows me to learn how the weapons were constructed, poor design characteristics, sighting issues, reloading, operations, etc. As I like military history, it makes it more real for me. Restoring two Krags at the moment and three Swedish Mausers, a 94, 96, and a 38.

One side benefit of this mess, if you continue, you will learn A LOT about the function of the AR 15 parts and how they operate properly.
 
I'm not sure I understand what you are doing.
Are you trying to assembly M16 lower parts in a semi-auto receiver?
What gas piston are you referring to? The AR doesn't have a piston.
If you scrap the LPK from the M16 the only thing you need is a standard small pin LPK.
 
Gas piston or gas tube? There is no piston on the AR.

That said, I'd rather buy my parts all from one supplier than from numerous suppliers and gun show specials. You never know what you get from the latter. It could be rejects, recycled, or even stuff salvaged from some mfg's garbage.
 
I did mean gas tube, I've already assembled the lower and it works good on my Bushmaster upper M-4. The pin that went thru the hammer was too small so I went into my parts kit and corrected that. The gas tube he had was for a 20", and he wants a 16" barrel, so I got one of those for the 16" barrel, and the fore end as well. I forgot to mention that, on the lower, I put the correct safety switch on the lower intended for a semi-auto.

Now I've got the front sight base ordered for the new barrel, and once that get's here I should be able to complete the assembly of the M-16 upper receiver. Hopefully it will work, however if you knew my friend, you would understand the way he tries to save money, and in the end he pays entirely too much and usually ends up on the short end of the stick.

I've assembled quite a few AR-15's but I've always used excellent parts, and have had great results, this is the first parts gun that I've ever attempted to assemble, and by all means it best be my last.
 
Colt only used larger pins on their civilian ARs to prevent installation of military fire control parts. They recently changed back to a standard pin size for all, military and civilian. Of the M-16 specific (full auto) parts, the only unmodified to semi part allowed in a semi build is the bolt carrier. No unmodified to semi M-16 selector, hammer, trigger, or disconnector allowed. ATF does not smile kindly on that.
 
BBBill, he's got a Spikes Tactical lower, the pins he had were from an older Colt M-16, believe me I wouldn't take a chance on rebuilding a full auto. I myself was once a law dawg, so I do know the ramifications. The upper receiver is from a M-16 or so he says. I do know it is in pretty rough shape, however, I've got the barrel inserted in it, now Like I said before all I need is the front sight base and it should be completed. I'll put a photo up when I complete it.

Incidentally I installed the standard trigger, and sear from a DPMS parts kit.
 
BTW I thank you 243, I did check that post however, I never ran across the dilemma I've been experiencing. Nor has anyone else. My buddy stated he got the parts from an old army buddy back in Philadelphia. Anyway when I'm done he is going to have just an AR-15, I do know that he did get the Spikes lower receiver with the serial number around here as he had the receipt, so I'm sure that was registered.
 
Anyone interested can see the finished product by going to "AR-15 Parts Gun Completed" as I couldn't find it on this section, thus I had to start a new thread. Guess my eyes are going too.
 
The M16 parts sets on the market are for 20" light barreled A1 rifles that are different than the M4 configured carbines. Nobody here knew that?
 
Most people don't buy used parts, or have possession of the parts, (he was given the parts) Like I said the fore end was for a 20" barrel as well as the front sight which would not fit the 16" barrel it was too small. Also the gas tube was too long as it came from presumably a m-16. I should have mentioned that the safety selector switch was also from an m-16, which I placed a DPMS switch on it, as well as the sear. My buddy got the vast majority of the parts from an old military armorer that had recently passed away, in Philadelphia, Pa recently. I did get the parts together as you can see by going to the thread I mentioned earlier. The only problem was when I attempted to shoot 52grn. hand loads thru it, it started to eject and jammed the next round in the chamber. (one time) Every thing else worked fine as I had some 55grn. as well as 60grn. 5.56 ammo, and was mentioned previously was very accurate out to 100 yards.
 
Last edited:
Older front sight bases were .625" bore for the original "pencil" barrels. Current M-4 profile is .750", but you can find new/used barrels in either size as well as some non standard diameters. Small diameter barrels fell out of favor for a while, but there's a renewed interest in lightweight guns, especially for female shooters. I've been contemplating such a build for my wife. I was about to decide to just get a standard M-4 profile and turn it down. The option there would be to leave the front sight base seat at .750" while reducing everything fore and aft to remove weight. I may just opt to buy a current production pencil barrel now that they're more available.
 
BBBill, Sounds like a good idea, be sure and give us a few photos of the finished product. I've got a Bushmaster Upper in a M-4 design on a CMMG lower, that my wife seems to shoot just fine.
 
I'm gonna have to get a photobucket account I guess. The wife is finally getting more serious about shooting after all these years. She's very petite without much upper body strength. That's why the lightweight build.

Surley said:
If you really want a parts compatibility nightmare, start building multinational AKs.
Click to expand...
Yep! True dat!
 
Status
Not open for further replies.
Back
Top