Questions on full auto parts & the AR


March 8, 2011, 08:42 PM
Doing a search here didn't reveal any recent posts on this topic, so I thought I'd check for updated info. For example: It's my understanding that the possession of fire control parts that can be used to make an AR15 operate full auto is not illegal provided one does not also have an AR15 that the parts can be installed in. (Please note, I'm not arguing the wisdom of not testing this law.)

I recently found that my Colt SP-1 1980 vintage has some M16 style parts in the fire control system when discovered I could turn the selector to the full auto position. But it does not have all the parts required for full auto. The parts required are the selector, the trigger(?), the disconnect, the hammer, the bolt carrier, and an auto sear (and optionally a burst fire cam).

Of these I have found that my gun does have at least an M16 selector and hammer. The disconnect I can't determine by looking down into the receiver (I haven't yet disassembled it). However it is missing the auto sear and the M16 bolt carrier, so it cannot operate full auto. I suspect the most it can deliver is an occasional slam fire.

I have ordered AR15 parts to replace these to be sure that I'm legal. But there remains some puzzlement. To start with, why would someone would put these parts in it without being able to complete the job? The lower receiver does not have the pin holes required for the installation of an auto sear.

The background on the SP-1 is that initially Colt provided a milspec receiver with the exception of the auto sear pin holes. Later, to discourage rampant modification, Colt added an auto sear block and enlarged the pins for the trigger and hammer so milspec M16 parts could not be installed. Then toward the end of the production, Colt stopped milling out the area where an auto sear is installed and went back to the standard pin sizes. This was all done for CYA, not to comply with ATF regulations.

The issues I'm pondering is what specific parts are banned and what constitutes a rifle capable of having these parts installed. My SP-1 does not have the sear block, and though the area of the auto sear is milled out, it does not have the pin holes to install an auto sear. This leads me to wonder if possession of this gun makes the possession of the parts illegal. As I understand, the ATF initially considered mere possession illegal but changed to also require the possession of a compatible gun by court ruling.

I've found research of this ponderous since complete information isn't readily available. For example, some sources seem reluctant to even mention an auto sear, while being quite open about the other parts. Others who offer original Colt M16 kits for sale (such as Sportsman Guide) state that they do not come with the lower receiver (of course), the disconnect, and the original barrel (a new AR barrel is substituted). But from the picture provided it's obvious that the hammer, bolt carrier and selector are all original (no sign or mention of an auto sear). Thus I deduce that the true illegal parts may be the receiver, barrel, disconnect and auto sear.

Since M16 components are openly sold with selector and hammers, I was considering the possibility that Colt may have at one time provided these parts in their SP-1 to consume their supply of M16 parts rather than milling new parts. This then would explain the presence of these parts in my AR without it being capable of an auto sear.

Can it be?

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March 8, 2011, 11:05 PM
Without the autosear theres nothing wrong with M16 parts in your rifle.
Chances are your lower wont even accept the autosear, seeing as its a civilain model, but you can buy autosears online for like $2.00

The only way to make it accept an auto sear is to drill a hole, and THAT is construction of a F/A weapon.

Drilling the hole is the only illegal thing you can do.
Also IANAL, but thats how I've learned it

March 8, 2011, 11:21 PM
How many years in the federal pen can you get for just drilling a hole? 15? 20?

Auto gun laws need to be revoked, pronto.

March 8, 2011, 11:36 PM
Thank you very much for confirming my suspicions. It all makes much more sense now. I would absolutely have to drill a hole to install an auto sear and that would certainly be a violation of the law. I believe the penalty is something like 10 years in the slammer and a $20,000 fine. Regardless, to avoid any doubt I have replacement AR parts on the way and I'll enjoy the task of switching them out.

BTW, what might be your opinion on a full set of original military issue M16 parts sans the lower, disconnect and sear, and with a new barrel (unknown origin, in one case white metal and the other parkerized with sight/gas block installed) for $475 with a choice between an A1 or A2? I'm sorely tempted.

March 9, 2011, 11:38 AM
Considering that this:
Is 600$

475$ seems like a good price.

March 9, 2011, 12:45 PM
Considering that this:
Is 600$

475$ seems like a good price.
SG is overpriced. Those kits are $499 at most places.

March 9, 2011, 12:48 PM
SG is overpriced. Those kits are $499 at most places.
Welp, then $475 is still a good price :D

March 9, 2011, 01:03 PM
These are in various states of used condition but have new barrels. They also have A1 kits with raw metal barrels for $500.

March 9, 2011, 06:00 PM
Be careful. Possession of an AR-15 that doesn't have the auto sear hole drilled, plus possession of the full auto parts, does not mean that you have a rifle capable of full-auto fire. However, it does mean that you have a rifle that's "readily convertible" to full auto fire. (After all, how long does it take to drill one hole?) That's the same thing to the BATFE.

March 9, 2011, 07:14 PM
Be careful. Possession of an AR-15 that doesn't have the auto sear hole drilled, plus possession of the full auto parts, does not mean that you have a rifle capable of full-auto fire. However, it does mean that you have a rifle that's "readily convertible" to full auto fire. (After all, how long does it take to drill one hole?) That's the same thing to the BATFE.
And around we go, which is why I came to ask about it here. The law basically says that you cannot own full auto parts and a gun that can accept them to fire full auto. How about if you only have some parts? Is a gun undrilled for a auto sear constitute a gun capable of accepting them? An M16 bolt carrier is legal in any case. How about an M16 selector? Hammer? Is it ok if you have some parts but not all? If they are all illegal, then how can M16s with some of these parts (minus the lower receiver) be openly sold? Or do they only become illegal when you buy a lower? Finally, if they are illegal, why are the companies able to include these in M16 kits but not the disconnect and auto sear?

All they need is a law against one part, the auto seer. (In fact, all that they need is a law against machine guns.) Without the sear none of the other parts mean diddly.

I did not keep these parts. There is no reason in God's green earth that I should. They probably detract from the value of the SP-1 because they obviously are not original. The ATF can probably twist these laws to nab you if they wish, which is probably why the laws are so disjointed. So it is folly to take the risk. I only ask out of curiosity... assumptions and what ifs only serve to make my head hurt. =o)

Jim K
March 9, 2011, 07:22 PM
It is highly probable that the rifle came from Colt with those parts installed. Colt sold many of those rifles with some M16 parts, with no objection from the feds, and BATFE has no problems with those rifles today.

I wouldn't worry about it.


March 9, 2011, 08:01 PM
The first run of Colt AR-15 SP-1 sporters was approved by ATF based on the redesign (from the M16) of the bolt carrier, hammer, trigger, disconnector, and selector, as well as obviously the absence of the auto sear. It was found, after the guns were on the market, that anyone could simply remove the disconnector, and then the gun could go full auto (after a fashion) by the hammer riding forward as the bolt carrier slammed shut. Because of this, Colt quietly removed the gun from the market for a time (btw, this gave an opening for the Armalite AR-180, which for a while was the only equivalent gun available). When the AR-15 reappeared (circa 1972), it had been redesigned again so that a notch was added to the hammer, and a bevel to the carrier below the firing pin, so that if the disconnector was removed (and the trigger held down), the hammer would catch on the firing pin and jam the gun. Later, Colt made further changes, for example, putting a hardened block in the back of the lower receiver to prevent the drop-in auto sears of the time from being installed.

It's interesting that none of these early AR-15's were ever declared illegal by the ATF. In effect, they're "grandfathered in" as long as the original configuration of parts is maintained.

When aftermarket lower receivers appeared, along with plenty of surplus GI M16 parts, the quiet cooperation between Colt and the ATF was no longer enough to keep a lid on the situation. I remember a time, back in the early 1980's, when it was a selling point for AR-15 builds that they contained "all GI parts." That's about the time when the ATF came out with a circular (I was a Class III dealer at the time) that said that an AR-15 with any of the five named M16 parts was a no-no. I remember there was a mad scramble to replace the questionable M16 parts with proper AR-15 ones.

I get the impression that the rules have relaxed somewhat since that time.

March 9, 2011, 10:51 PM
Very interesting, thank you Alexander.

My SP-1 dates to about 1980. The bolt carrier does have the portion below the firing pin beveled out. In addition, when I discovered the selector could be set to auto, I tried repeatedly racking it to see if the hammer would be caught. It didn't, but occasionally the carrier would get stuck half way forward, no doubt from the hammer jamming on the firing pin just as you said.

I wondered if the thing would auto fire just from the hammer following the carrier forward, which would be more like an assisted slam fire. But none of this could be very healthy for the internals.

It's kind of comical how I found out about it. I was having one of those DUH moments (I've actually been having more of them with age). :scrutiny: I had just gotten the SP-1. I switched it to the fire position and noticed that it could be turned about 30 degrees beyond fire. :scrutiny: :scrutiny: I switched it back to safe, but something didn't look right... it was pointed upward. :what: My immediate thought was someone had installed the selector 90 degrees off. :cuss: I was trying to figure out how that was possible when it dawned on me... the damn thing was uncocked, so I shouldn't be able to switch it to safe. I cocked it and sure enough, I was then able to turn it all the way forward to the real safe position. :uhoh: I looked into the receiver and saw it had an auto selector cam. I could have sworn I heard black helicopters hovering overhead. :eek:

Now the parts are out and the lower is waiting for the replacements. One nice thing though, it's in good condition. :cool:

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