DPMS upper receiver/ barrel alignment pin issue

[lakeracer69]

I decided to build my own upper and purchased a new DPMS upper receiver, and a Krieger barrel. I have finally received both parts and found an issue. The notch in the upper receiver that holds the alignment pin is .125" and the pin on the barrel is .134". The machinist in me says to take .005 off of each side of the notch. Is it common to have to do this?

 

I'm no stranger to "custom" work and it's an easy fix for me ( I have a mill with a DRO). I'm just wondering if that's a common issue. I would think, if anything on the gun,  that  would be standardized.

[bubbasks]

Mine took a wee bit to fit but possibly they made it larger in order to fit better to your rifle. Idk but better than being too small

[survivalshop]

You want it tight , with a light force it should seat. Be careful if you decide to take some off for fitment , its an alignment pin for a reason.

[lakeracer69]

Problem solved, I remeasured when all parts were at the same temp as well as calipers and was a little closer than I thought. I realize that it needs to be pretty close for bolt lock up. Does anyone have an actual spec/ tolerence on the notch width?  A .125 diameter pin should have a .001 or so clearanceI would worry if someone just used the barrel nut to jam on a barrel and cause any kind of an interference fit that would stress the front of the upper. I do know that anodizing adds a little thickness too.

[blue109]

As a graduate (with honors) of the caveman gunsmithing academy.....I vaguely recall having to use my delicately calibrated rubber mallet to get my RA barrel seated.

[lakeracer69]

Thanks for the replys, it's a non issue now. I'm more concerned that I could only find a lightweight DPMS A3 upper to buy. I have enough cash invested so far and didn't want to go the billet route. The more metal between my face, .308 rounds and reciprocating parts the better.

 

I'm still waiting on my bolt, to arrive so I can rent some gauges and check the headspace.