Letter gun?

[newchi]

My theory is, a factory make receivers, boxes and boxes of them.  Someone takes the receivers and puts numbers 1-99 (or whatever) on them all day long.
Someone else has a job of taking receivers out of the box on his work station and finding a barrel that fits just right, when he does he stamps it to match and dumps it in the wheelbarrow going to the next work station (or on the conveyor belt or whatever)  there might be 10 guys putting receivers to barrels, all with their own stamps set.
The barrels were all numbered after they were fitted to the receiver, imo as the numbers are all in line with the lining up line.

[Loose}{Cannon]

This whole paired numbers bs has irritated me since day 1.  Why do it in the first place??  Were they intending to later strip off all the barrels, mix them up, then put them back together again for craps and giggles??

The only reason I would think to remove the barrel is to replace it, and in that scenario you would be tossing the barrel so you dont even need a number on it.

My current theory of choice is that these numbers are fitment numbers used in the same manor as the barrel numbers for (what we think) to match up size wise to the RSB, gas block, stock ferrule, and FSB.

Basically it would represent a dimension of the threaded barrel socket of the receiver and visa/versa the threaded male shank and lug of the barrel. (lets say) the numbers represent a fraction of a millimeter. In this case the highest number observed would be .36mm which is just about .014 thousands of an inch.  I think its entirely possible to have a maximum tolerance variation across production of .014" or less. 

That being said when a worker milled a barrel shank, a dimension was measured. If the perfect target size is say 40mm and its over that number by .09mm  ....  its marked with a 9.

You do the same thing with the receiver, you can literally have barrels and receivers marked in bins ready to pull for a perfect match.  I would assume this measurement would be the barrel shank to mating flat so that the pair will index on the first attempt rather then having a worker failing to index barrels all day.

[Loose}{Cannon]

Put it this way....   RM may back me up on this one.

If you DONT do this during the production...

A: You have a high failure rate of indexing barrels
B: You have to mill the receiver face on nearly EVERY single receiver until index is achieved.

If B, welp.. then you end up with a LARGE tolerance range from gun to gun on the back end of the bolt requiring major differences in length for headspacing....  more time and milling and a VERY LOW probability of interchangeability.

No....  you do as I described in my previous post and avoid ALL of that.

[Loose}{Cannon]

You absolutely HAVE to devise a way to properly index lug flats and achieve consistent insertion depth into the receiver to ultimately save time, minimize drastic head spacing lengths of the bolt, achieve interchangeability, or at least reduce adjusting requirements of the bolt to head space.   

[newchi]

Well, i like that theory too.
measure the parts, stamp a number, assembly monkey just has to find 2 of the same number and match them.
I wonder if they were on the table face down and you took turns flipping them over?

That would explain the limited range of numbers nicely as well.

[Loose}{Cannon]

Turns flipping?

The parts would be in bins labeled with corresponding number.

[Power Surge]

Turns flipping?

I think he was making a joke 

Like a game where you had to find the matching barrel 

[Loose}{Cannon]

Yeah... no flipping.   The point of numbering and bin filing is to prevent flipping.