Another Newbie Question - Take-down Pin Hole > AR-15 / M-16 Retro Forum

Posted: 12/7/2007 10:49:35 AM EDT

I didn't find anything in the archive on this.

Is it unusual for the take-down pin hole to be slightly oval, front to back (I'm assuming the pivot pin is the one in the front)?

Is it a problem?

Is there a fix?

Thanks,
Bugs762

Posted: 12/7/2007 10:52:57 AM EDT

[#1]

Ooooohhhh. None of the several hundred I've seen were like that...

Posted: 12/7/2007 11:47:53 AM EDT

[#2]

Yes, I believe it is. Normal, that is. I would guess to ensure the uppers and lowers would always shut and latch up.

I'm assuming we're talking about the hole in the upper receiver? The hole in the lower receiver needs to be round.

Posted: 12/7/2007 11:55:15 AM EDT

[#3]

Quoted:
Yes, I believe it is. Normal, that is.

It is? I've never seen a oval hole in any of the receivers I have built up and/or sold to people or, for myself

Posted: 12/7/2007 12:56:37 PM EDT

[#4]

Quoted:

Quoted:
Yes, I believe it is. Normal, that is.

It is? I've never seen a oval hole in any of the receivers I have built up and/or sold to people or, for myself

Oh sure! You made me go measure things.

Here's my results:

Stag flat top w/M4 cuts, ~ 9 months old - 0.265" x 0.245"

Colt Model 604 (M16) - 0.265" x 0.245"

Colt Model 603 (M16A1) - 0.267" x 0.244"

Colt SP1, age unknown - 0.282" x 0.245"

Colt Sporter Match HBAR, mdl 6601 - 0.277" x 0.248"

Again, these are the dimensions for the hole in the rear lug of the upper receiver. They are oblong.

Posted: 12/7/2007 1:47:36 PM EDT

[#5]

Yes, the take down pin hole in every upper receiver I've seen was visibly oblong, with the horizontal dimension being larger than the vertical. By contrast, the front pin hole in the upper is always round.

Posted: 12/7/2007 3:37:28 PM EDT

[#6]

Quoted:
Yes, the take down pin hole in every upper receiver I've seen was visibly oblong, with the horizontal dimension being larger than the vertical. By contrast, the front pin hole in the upper is always round.

Yes the upper receiver, that is what I am seeing.

Thanks,
Bugs762

Posted: 12/7/2007 5:55:13 PM EDT

[#7]

All 5 of my upper receiver takedown pin holes are horizontally oblong also.

Posted: 12/18/2007 7:42:50 PM EDT

[#8]

Always assumed that the oval hole allowed for some tolerance stacking, and also for expansion when the upper gets warm.
Moon

Posted: 12/19/2007 1:07:03 PM EDT

[#9]

Quoted:

Quoted:
Yes, the take down pin hole in every upper receiver I've seen was visibly oblong, with the horizontal dimension being larger than the vertical. By contrast, the front pin hole in the upper is always round.

Yes the upper receiver, that is what I am seeing.

Thanks,
Bugs762

And those who have posted otherwise have never taken a close look at their uppers