AR sear block questions

[tomob1]

OK, i admit it, I only own 1 colt long gun, a preban AR in 9mm. I'm the second owner. when i bought it the sear block had been removed (seller informed me of this). I've seen other preban guns for sale with the sear block removed.
now the dumb question: why remove it?
thanks
tom

[Malysh]

The sear block has to be milled out if the owner wants to use a registered drop in auto sear in their lower receiver. It's usually referred to as RDIAS. There are probably examples done where the owner just doesn't like the idea of the sear block and had it removed, but why bother unless you have the registered auto sear? If a lower has the sear block milled out and there is an auto sear pin hole drilled at 12:00 above the selector switch then you know a previous owner used the lower for full auto or 3 burst fire. A lower with the auto sear pin hole drilled would be an NFA item, just like an RDIAS is an NFA item. At that point, the hammer, trigger, and auto sear pin holes should be checked for any deformation or very hard usage. Likewise, an upper that might go with it should also be checked for hard usage before buying.
It is legal to remove the block even without owning a legal RDIAS as long as the auto sear pin holes are not present. There are many examples around that have the auto sear block removed, but were not drilled for the auto sear pin hole. These are perfectly legal semi auto rifle lowers.
HTH

[tomob1]

thanks for the info. i've had the gun for a couple years now, but it was like new when i got it and no "extra" hole.
saw that m16 parts are available from cheaper than dirt, so i wonder how many folks are converting their AR's to full auto (legally or otherwise)? maybe thats what the previous owner was planning. can't see why having it removed if not.
tom

[Malysh]

Happy to help.
There are a lot of Colt SP models legally converted to full auto M-16s out there for sale. All were made before the laws or ATF policies were changed. The SP series all had the conventional hollowed out area where an auto sear could fit. I forget what series Colt started incorporating the sear block in the design.
Other manufacturers offered the traditional lower receiver design, but Colt changed it on their civvie rifles because for many years they were the primary military rifle supplier and they wanted to keep Uncle Sugar happy.
HTH

[ColtDogg]

If I recall, Colt did Sear Blocks back in '89 to do something with the Ban. It was not a must from what I was told. I was only 15 years old at the time and just only dreamed of guns. I own a Colt now that was a 89 to 94 gun and it has had the sear block taken out. Just seems like all the cool guns I like was the Pre-89 guns. Green label Colts, Old AK's and the 9X HK guns. You know,,,, The real KOOL guns. Not the clones like you see now days.

[tomob1]

thanks again for the info. so, my colt may have come from the factory without the sear block?

hey coltdogg, where in OK are you? I'm in NW kansas and take 35S on my way to dallas a few times a year.

tom

[ColtDogg]

thanks again for the info. so, my colt may have come from the factory without the sear block?

hey coltdogg, where in OK are you? I'm in NW kansas and take 35S on my way to dallas a few times a year.

tom

I am North East OKLA. I am in Claremore OK, just next to Tulsa.

Now your AR may came with out a Sear Block. I took a few pic. of mine that had it taken out to show some pic so you will know what to look for.
I am not 100% if it will help, cause I only had on 9mm in my hands one time. It had a sear Block in the gun. The funny thing is the box is a Green Label. I looked at the SER. of the box and the gun and they are both the same. Now I did hear of a few late Pre-89 guns did come like that as it was going from Green label to Blue Label.


Now hear are the pic. Look at the pin over the selector. That is a pin to hold the Block in.

Now on mine, the pin is only in one side of the gun. the right side.
I have seen some that will go from left to right. It is almost as big as the Selector.

Now here is a pic. of the inside of the lower. If you look right behind the Selector it can see what looks to be a Roll Pin that goes down in the lower.


Now me Green Label R6600K gun I have don't have any of them.

Also here is a link I found . Look at pic. 4 and 5. Pic is like the pic. of my Colt. and Pic is the pic. of one still in gun. as you can see the block has a hole in it so you can get to that Roll pin. I hope this helps. JB


***** Now if I am wrong in any way,,, some one tell me. I been playing with the guns like this from the mid 90's but I know I do now know everything about them (YET!!)

[JudgeColt]

The information on the drop-in auto sear is incorrect. A drop-in auto sear does NOT need the hole above the selector being discussed above. A regular M16 auto sear needs the hole, since it pivots on the pin that goes in that hole. A drop-in auto sear is held in place by the lug on the upper receiver through which the rear locking pin goes to lock down the upper receiver to the lower. It just "drops in," hence the name. No removal of pins or the like is needed. The auto sear body carries a substitute hammer trip that takes the place of the M16 auto sear that pivots on the pin above the selector.

If a semi-automatic AR lower receiver was legally converted to full-auto, it remains a machine gun forever more. Removal of the auto sear and pin does not change the character of the receiver. On the other hand, a registered DROP-IN auto sear is the machine gun and can be used in any AR platform that will accept it, and it will work full-auto provided the AR has an M16 bolt carrier, selector, hammer and disconnector.

Colt and some other AR platform makers added measures to prevent the drop-in auto sear assembly from being "dropped in," since there were a lot of unregistered drop-in auto sears sold in the 1970s and 1980s. THAT is the purpose of the block and lower receivers without lower receiver cavities that will accept the drop-in auto sears.

[JudgeColt]

I need to clarify that the Colt sear blocks also have a pin above the selector. It is a blind pin in that there is no hole on the other side, which prevents the pin from being driven out and the block removed without machining it out. The diameter of the pin is larger than that which would be used for an M16 auto sear, presumably to prevent an M16 auto sear from being put into the receiver if the block is removed and an appropriate hole is drilled into the other side of the receiver.

[ColtDogg]

I need to clarify that the Colt sear blocks also have a pin above the selector. It is a blind pin in that there is no hole on the other side, which prevents the pin from being driven out and the block removed without machining it out. The diameter of the pin is larger than that which would be used for an M16 auto sear, presumably to prevent an M16 auto sear from being put into the receiver if the block is removed and an appropriate hole is drilled into the other side of the receiver.

I am still not sure. I have not took any calipers to the lower, or the M-16 sear I have . But I did think about the Sear pin being smaller then the pin that Colt did put on the gun. Now Colt has a bridge in the lower. to stop any of this. I took one of my lowers down to see what it would run to get it taken out and the guy said about 400.00 to 500.00. I did not buy the Auto Sear I was looking at so I did not get it done.