Home Forums Hunting & Shooting AR and Tactical Rifles Upper receiver question

Hey everyone,

I am pretty new to the AR world, but have a question on upper receivers. I have seen a number of ads for upper receivers saying "complete" or "replacement" upper, but then it usually states that the bolt, bolt carrier, and charging handle are extra.

Without a bolt included on these how are they headspaced?

They use a "generic" bolt to set the headspace... there are tolerances and specs on the bolts... Such that using any bolt that meets spec " SHOULD" work safely... Doesn't always work like that but most of the time it does assuming you are not buying junk from a junk dealer so to speak.

ros..,

I have a friend who was a green beret. His specialty was small arms. When I posed the question of headspace to him, he said the bolt 'set' to the upper after several rounds and wasn't supposed to be switched to another upper after firing. Seems odd to me. Ever heard of that?

O

I have carriers that have bolts that have been checked in various uppers of mine... I swapped them back and forth all the time.

I think your green beret friend is remembering incorrectly or he was the victim of an old wives' tale.

With today's CNC manufacturing, part swapping is very common and unless there is a defect in the parts to begin with, the wear on the parts will be the same regardless.

I may have been more prone to agree with your green beret friend, if he had said that after several thousand of rounds it might be unwise to use a bolt in another upper, but after several rounds? Nope. That is not reality.

Interesting. My friend is the real deal, currently a Col. over an ordanace batallion, just got back from Iraq. However, his green beret training was over 10 years ago.

Being an old bolt gun guy, headspace has always been a consern of mine. It just seems strange to slap parts together and start shooting.

O

Not everything they tell ya in armorer school applies to real life. That plus the military, on our dime, can afford to not use things twice if they so decide.

It is good practice and one of the things required by a MIL armorer, checking headspace that is, when changing bolts or barrels. But I have never found one that wouldn't check ok and I've seen some well used bolts so I don't doubt that your buddy believes this to be true.

It is also believed in some circles that once a bolt has several rounds fired, it kind of wears to that one barrel extension and if you run it in another gun it can cut the life of the bolt short.

IME, uppers, bolts, etc and replacement barrels are manufactured to very high tolerences. The barrel flange located on each barrel, acts to set the headspace, so when clamped in place by the barrel nut, things work, and work well. This has been my experience at least, with my gun in replacing barrels, and checking fired case dimentions from the old barrel to the new.
I`m not a smith, just have done this change out on my rifles, and again have been very impressed with how close each manufacture has held specs. YMMV.