Trick to Installing M4 Auto Sear Pin?

[Jmacken37]

I popped out the auto sear on a FA lower to put in a Geissele SSF trigger and am failing at re-installing the auto sear. What is the trick? Whenever I put tension on the spring's "long leg" the "short leg" seems to intrude into the bore of the bushing preventing me from inserting the pin.

What is the trick? I tried google and youtube with zero success.

[Iraqgunz]

You need to install the pin from the right side as I recall. It also needs to be in the AUTO or BURST setting when doing this.

[drh2687]

If you tuck the long leg of the spring behind the long leg of the sear itself, you should be able to just drop it in without having to tension the spring by hand. Makes it a bit easier. Just ensure the tip of the long spring leg winds up on the FRONT (muzzle-end) of the selector. This should get the short leg out of the way of the pin.

Regards to the pin itself, it SHOULD go in from either direction, but as Iraqgunz said it may be easier from the right for whatever reason. As long as the spring winds up in the detents on the pin, you're golden.

Also, I typically install the autosear before I put the trigger/hammer assemblies in. Sounds like you already have the SSF installed. Not sure of the particulars on that trigger, or if the sequence makes any difference.

[Iraqgunz]

The tech manual states the pin goes through the right side. If you attempt to do it through the left side you will damage the spring. The reason for this is that the sear spring when folded into position position captures the sear pin on the right side with tension. I may be wrong because I don't play with the sear all the time but that is how it is stated in 23&P and how I have done it.

[drh2687]

Not looking to be argumenative here IG - simply trying to understand why we have different info. With any luck, learning may occur...

I checked out the 23&P here: http://www.cpi-va.us/docs/M16Manual.pdf Page 3-59 shows reassembly of autosear, but I couldn't find a reference to right or left side in there. Did I miss it?

My manual from the Colt armorer course says only to cross the spring leg over the sear, position the sear, and "Step 19: Insert automatic sear pin." I snapped some photos of the manual, but can't get them to upload from my laptop for some reason.

My confusion is this: there are spring detents on either side of the pin which are equidistant. Even if you insert from the right, that short side of the spring is still going to catch and then pop out of the left detent channel as it passes under the spring. If bending it is a concern, I'm not sure how going in from the right gets you around that.
l_160000380_2.jpg

Quite frankly, this is purely academic. For the OP, just play it safe and put it in from the right and we can all sleep soundly tonight.

Thanks for the distraction gents. Back to work!

--David

[Ned Christiansen]

I find a lot of them where the chamfer on the end of the pin is not quite enough to ramp the detent spring leg outta the way (that's the part you're talking about that protrudes into the hole; it's supposed to). I've made a little tool-- I don't sell them but easy to make-- a 1/8" pin with a 45 degree hypodermic-type point. It goes in from the left side and holds all in position, plus, the point goes opposite the detent, then you rotate 180 and it lifts the detent out of the way make it real easy then to slide the pin into place. You need to push the tool with the pin for a smooth hand-off. You can do it from the other side too, then you don't have to go past the first detent groove in the pin.

Or just file or stone a little more ramp on one end of the pin, doesn't have to be a full chamfer as long s you line it up with the detent.

None of this will work if you're trying to use a hammer/trigger pin as the autosear pin, nyuck nyuck (they're 1/32 larger).

Can't take the time to post a pic but if you Email me I'll send you a pic and you can post it.

[patrick sweeney]

I've seen Ned's little gizmo, and it is slick and easy.

Yes, the design intent is for the autosear pin to can the short tip out of the way, but we all know what real life does to plans.

We struggled through a bunch of classes, trying to assemble the frakkin autosear pins as the manual says, and then Ned shows up with his tool. Now life is good.

The only problem is, it is so simple there's no way to make a living at selling them.

[Jmacken37]

Ned C..jpg

Ned's tool was the answer!