Options on removal of the sear block in a Colt

AR/M4 AR Technical Discussion
1

Guys, I have a Colt 20" A2, that has the funky steel sear block in the lower receiver.

I thought I remember talk of one of the larger named smiths being able to remove this and leave the remains of the steel anchor pins in the lower.

Is this possible and if so, who would you recommend to do the work.

I really would like to be able to run a standard bolt carrier in this rifle.

Thanks in advance.

2

Have it machined out or you can leave the block but have the stud machined off. Any machinist can do that.

3

By standard carrier, I’m assuming that you mean M-16 carrier, as it should be standard in every rifle. But to let you know, you can run most AR-15 carriers (depending on the amount of material removed by the manufacturer) in sear blocked Colts. I replaced the C-shaped carrier with an LMT AR-15 carrier in Sporter LW.

4

Here is a PICS thread from ARFCOM on doing this with a dremel. I looks like it came out pretty good…
SEAR BLOCKS meets DREMEL

Rmpl

5

Out of curiosity, why would you want to remove it? Thanks.

(Wouldn’t the standard m16 carrier work?)

6

Thanks for the info guys. I hadn’t thought things through and hadn’t tried a M16 carrier in it, but I will now.

Thanks again.

7

Because if your lower has this block in it, you cant use a M-16 carrier.

8

Another option would be to buy a new Colt lower without a block (do this FIRST!) and sell the lower to someone in New York, a slave state, since it appears to be pre-ban and has a front push pin (most desireable, those folks have bucks and don’t want no stinkin’ SP I/II’s).

Just a thought.

9

Templar,

That rifle has the sear block pinned from both sides. The pin looks like a countersunk machine screw on both sides. The large part that you see from the receiver is like the top of a countersunk screw.

If I were you, I would not remove the block completely as the countersunk pins will probably just fall out, leaving the countersunk hole in the receiver behind.

The colt rifles that have the sear block pinned with a straight pin from the right side are the ones that are good candidates for complete sear block removal. The block itself is removed, leaving only the pin in the side of the receiver. This pin will not fall out like the double counter sunk pins.

Even still, I don’t bother removing the sear blocks. I simply make the sear block flush or nearly flush with the top of the receiver.

I have done four colts like this on a bench grinder. All you have to do is be meticulous and go slow as to not overheat the material (a wet sponge also helps). Once it is flush with the top of the receiver, put a little cold bluing chemical on the bare steel.

This, like others have stated will allow the use of new production Colt uppers and their M16 bolt carrier groups.

10

Thanks!

11

What purpose does this sear block have if any? forgive me, I’m still few in the AR world.

12

Colt started putting them in their rifles after the 1994 Ban, to keep people from putting auto sears in and using M16 bolt carriers…

PC BS but from Colt’s point of view, a necessary pre-emptive move. The state of Connetticut owns some of Colt, or did, and with their government contracts, they couldn’t afford to buck the system.

13

Colt makes an “enhanced” bolt carrier that is shrouded like the M16 carrier to protect the firing pin but is shaved at the rear so it works with the sear block. If you really need the extra mass of the M16 carrier, consider a heavier buffer.

14

I appreciate submariner.

I haven’t had any issues so far, the rifle is very reliable, I just don’t like having a rifle that I can’t use any carrier that I want in it.