New SAR build issues

[sparky923]

Finally got my new SAR kit build on ATI 13" barreled receiver out to the Range. Several surplus metal and Orlite mags both fit and function. Federal .223? fed and fired fine out of all mags at first, 5 rounds each out of seven Orlites and 10 rounds each out of four metal surplus mags. Ejected at 2o'clock.
Started second round of metal surplus mags when hammer follow started, with barely dented primers that fired on the second try. Pistol turned into a single shot until a case head separated and now its deadlined until I get a shell extractor.(Never needed one, in decades of shooting).
One weird thing I noticed was some kind of goop on the muzzle device, almost like I accidentally got grease on it from the workbench.
Any constructive, helpful, suggestions?

[boscoman]

For starters I would double check head spacing. Then go from there.

[lcastillo]

Head separation usually occurs when brass is stuck in chamber. When you clear brass check to see if chamber is not fouled up. A lot of the old Century Arms Golani’s needed a chamber polishing to put them on the right track. Century did not provide chrome or nitride barrels they did the basic barrels which tend to corrode and foul with use. I don’t know what ATI uses maybe it’s the same situation. Lou