Seekins Precision IRMT-3 Upper Truing Question Machining Mark

[trcloud]

I am building my first precision AR15.

I am really into Seekins Precision's thick wall barrel receiver mating mating area idea and ordered a IRMT-3 upper and their handguard.

While waiting for the handguard, I received the upper couple days ago and I noticed some machining mark on the receiver face shown in the picture below.

Hope you guys can see the little machine mark at the left up corner on the face. I am wondering if that's going to affect my precision. I am considering maybe true out that little imperfection but can the brownells ar receiver lapping tool get into this channel without massing up the threads? If true out that layer of material to clean the machine mark, will it mass up my head space?

 

[trcloud]

I measure the inner diameter to be a little bit more then 1.18".

 

[flyright]

It doesn't appear raised. Seekins builds precise stuff. I would check the flatness - if it's good, I would not worry about it. If not, lap it.

 

[trcloud]

It doesn't appear raised. Seekins builds precise stuff. I would check the flatness - if it's good, I would not worry about it. If not, lap it.

Yes I believe it't not raised. But if lap it out, the barrel will also seat a hint deeper, will that lead to any potential concerns?

 

[flyright]

Truing the face would probably not require going until that tiny imperfection is completely gone. If it's already true, I wouldn't worry about the imperfection.

 

[trcloud]

Truing the face would probably not require going until that tiny imperfection is completely gone. If it's already true, I wouldn't worry about the imperfection.

Let's say there is a dent on somebody's Surgeon or Defiance or Impact Receiver face and some body post it in the boltgun forum

 

[ironsight1000yard]

Hmm, interesting ...

 

[2ndamendfan]

Yes I believe it't not raised. But if lap it out, the barrel will also seat a hint deeper, will that lead to any potential concerns?

Please explain how you think lapping will lead to problems? Please think about it first, the AR style firearms are not assembled like bolt guns.

 

[2ndamendfan]

I measure the inner diameter to be a little bit more then 3".

inner diameter of what?? 3 inches really? A beer can is only 2 1/2 inches in diameter.

 

[trcloud]

inner diameter of what?? 3 inches really? A beer can is only 2 1/2 inches in diameter.

Sorry, the caliper was on metric. Looks like inner diameter is 1.180"

 

[TonyTheTiger]

Its garbage, but I'd still be willing to give you a few bucks for it.

 

[trcloud]

Please explain how you think lapping will lead to problems? Please think about it first, the AR style firearms are not assembled like bolt guns.

You are right, as long as the end of the carrier is not pushing the buffer it should be fine. But will that hole clear the tool?

 

[flyright]

[QUOTE=
Let's say there is a dent on somebody's Surgeon or Defiance or Impact Receiver face and some body post it in the boltgun forum

Yeah, I'm better at telling others what to accept than accepting it myself.
OP - send it back!

 

[flyer]

If the lap is too big, it could lap away some of the threads. If the lap is too small, it could leave a ridge that the barrel extension sits up on.

If the Mark is a gouge instead of a raised area, it should not cause any problems.

 

[2ndamendfan]

You are right, as long as the end of the carrier is not pushing the buffer it should be fine. But will that hole clear the tool?

The end of the carrier is always pushing on the buffer. Buffer retainer is only there to keep the buffer from hitting you in the forehead when you open the upper from the lower.

 

[Yondering]

Wow, some of the concerns here about parts have gotten crazy lately, and it seems to mostly come from guys who are new to ARs and don't understand what matters and what doesnt.

Just assemble that thing and shoot it. That tiny mark does not matter at all. You could do yourself a big favor and spend the time figuring out how ARs work (headspace, for example) instead of worrying about insignificant stuff like this.