New build, failure to extract spent shell, charging handle hard to pull back

[VASCAR2]

Some barrel manufactures don't drill the appropriate size gas port hole. There have been barrels sold with under size gas ports and many with over size gas ports. It can be difficult to tell the difference between under gassed and over gassed system on a new build.

It always helps to identify the barrel length, and gas system (ie, pistol, carbine , midlength, intermediate or rifle length). Manufacture of the barrel, whether Stainless Steel or CMV with type of rifling and twist doesn't hurt either as some brands are known to have issues. It's a good idea to measure the gas port diameter on a troublesome build that way it is easier to help diagnose the problem.