Need width dimension of upper receiver front takedown pin block

[Bret]

I bought three complete upper and three stripped lower receivers from the same manufacturer. Fit is nice on two pairs, but one pair has what feels like excessive side to side wobble at their front. I measured the width of the front takedown pin blocks (I don't know the technical terms for these) on each of the upper receivers and found they were 0.491", 0.495" and 0.498". What is supposed to be the width dimension and allowable tolerance of the front pin block? The manufacturer claims they have a no BS warranty, so I want to know what I'm talking about before I call them. In every other regard both the upper and lower receivers look great.

[AKDoug]

I bought three complete upper and three stripped lower receivers from the same manufacturer. Fit is nice on two pairs, but one pair has what feels like excessive side to side wobble at their front. I measured the width of the front takedown pin blocks (I don't know the technical terms for these) on each of the upper receivers and found they were 0.491", 0.495" and 0.498". What is supposed to be the width dimension and allowable tolerance of the front pin block? The manufacturer claims they have a no BS warranty, so I want to know what I'm talking about before I call them. In every other regard both the upper and lower receivers look great.

.500" +/- .005" one of yours is pretty narrow.

[GH41]

Front and rear on a BCM upper I have in front of me both measure .496

[Bret]

OK, I'll call them Monday. I don't mind a bit of wiggle, though I prefer none. This one is just more than I've ever seen.

[AM-15]

I would not stop there.
I would also measure the inside of the lower to cover all the bases.
My BCM4 upper is .497" mated to an Anderson lower which is .501"
My PSA upper is .496" mated to an Anderson lower which is .503"
Obviously one is sloppier than the other, the tighter one is my precision rig and the sloppier one is my fun gun.
They both function fine but I see where you are coming from.

Clarence

[BSmith]

So what's the spec on the mating side? With AM-15's measurements, and the above quoted .500 +- .005, you could realistically have uppers and lowers that don't fit together.

Sure it's not a +0-.005 or something on the upper?

[lysander]

.500" +/- .005" one of yours is pretty narrow.
Actually, it's .496 +0/-.003 inch, according to the Army drawing. Both the pivot and takedown lugs are to the same dimension.

The slot in the lower is .500 +.004/-0 inch.

.498" is too wide, but then again unless you are measuring it with a C-mike, you could be off a thousandths or two.

[Clint]

The lower width spec is .500" +.004 / -.000 or .500-.504"

Upper lower fit is not super critical.