Thanks for all the info!
Agreed, tight fit is best.
I only saw the above video after I did it.
My main concern with putting heat (torch) to something is normally I do that to a old/rusted part. Or if its a new part, the finish is not a concern.
I put the upper in the lower, so it was stable on my table.
Lubed it up and the barrel extension. (grease)
I got it to around 140F (using laser temp gun). I also applied heat not only to the upper's threads(which is what the video did) but the entire length of the upper that the barrel extension would go. Also some from inside of the upper shoving the flame through the ejection port.
Grabbed the barrel and it slide on just plot no resistance easy! By the time I realized how well it went on, it must have cooled enough(half a second!) I could not rotate it the 1/8" needed to get the little nub to line up with the upper. Doh!!!! I knew going into it will need to pay attention, but with doing it so fast I messed up.
This was partly the reason I did not freeze the barrel, I worried the heat transfer (steel to cerakote aluminum transfer heat???) could work against heating the upper.
Heated it a second time. Same as the first time. Got it rotated, slid down.
Was concerned if it was fully on or not. Heated a 3rd time, tapped with mallet on end of barrel. She is fully on!
Using hands applied pressure to keep the barrel pushed into the upper for the next 30 seconds or so as it cooled. Minimize risk of it cooling and ending up slightly crooked.
After watching that video, I would probably mount the barrel in a vice in the future and heat the upper like they did. Will pay more attention to the nub also. Next one I will get in one push!
Would like a better system to apply even pressure while the upper cools. Thought it was odd when they did it they just left go of it instantly hanging all angled. I know it cools fast. But what if it happens to work its way 0.001" as it cools/angles/walks.
Will get a 1" dowel if ever needing to remove it. Good idea, I would have just struggle fooked pulling like a retard.
Got this done last night, but took a while to get the upper hand guard to not be touching the gas block (slight shimming on the barrel nut to hand guard surface) to get it even.
Will probably have a thread in the near future on some trigger issues now....
