? on Colt Sear Block

AR/M4 AR Technical Discussion
1

Geissele does a nice job of explaining the small and large diameter pins in Colt trigger groups, with great pictures.

Now on the pictures of receiver with an integral sear block, I need educated on.

Figure 3 with integral sear block
http://geissele.com/colt-rifle-users-guide/

Please point out the integral sear block for this oldMan.

EDIT: Also is it necessary to measure each pin, wouldn’t just one measurement be enough:

From Geissele
Each pin needs to be pressed out of the receiver far enough to measure the pin’s diameter. Small pins will nominally measure 0.154 in. and large pins will nominally measure 0.169 in. as shown in the figure.

2

The extra aluminum in the area behind the selector lever and the rear take down pin.

3

I believe the sear block is the bulkhead between the rear pin and the trigger pocket. From the far right we see a pin, then said bulkhead, then the trigger pocket.

I don’t think any of them use different size pins for hammer vs trigger. However, it wouldn’t be a bad idea to measure both. I’d expect you’d be able to see if there’s any size difference between them, it’s around 10% which isn’t hard to spot.

4

Laughing at myself, for sure once you pointed it out, it makes so much sense. :slight_smile:

5

Just measured both, to be safe and both small pin

6

We’ve had some Colt rifles (I believe maybe 2 or 3 in the past 2 years) that had a small pin and a large pin lower. We would typically recommend measuring both pins just to be on the safe side. Colt is the only company to make large pin lowers between roughly 1988 and 2009.

-Geissele Customer Service.

7

Dang, don’t you just LOVE this forum!!!

Ask a question and the Pro’s From Dover enlighten us.

Again, dang this is a great forum.

OldMan OUT