Easy way to check FCG,

Cock the rifle unloaded while holding the trigger back, release the trigger slowly and disco should not release the hammer for the trigger to catch it, until the trigger is dam near all the way forward to it rest position (read like just a hair distance before to all the way forward when the disco releases the hammer for the trigger to catch it.  If the disconnector is releasing the hammer before trigger it almost all the way back forward, then disco is not timed correctly and could be causing you to bump fire the rifle if you dance the trigger at ignition/cycle.

The second problem could be that the disco is not retaining the hammer correctly until trigger release, which the bolt closing home hard, would be enough jolt for the disco to loose grip on the hammer when the trigger is held all the way back.  Most of the time this goes back to trigger release timing not correct, but on standard FCG, could be that the disco spring was not installed in the trigger large coil side down into the top of trigger channel.

So on that note, need to know what type receiver, if a 80%, what trigger in play, and could be as simple at just re-timing the disco to get it back into the correct release timing.

If you want to double check without have to do the trigger release, then just shotgun the upper open, cock the hammer back until the disco sear and the hammer rear sear are as close as you can get them without touching the trigger, and the hammer rear sear should pass by the disco sear with about a .004" gap between the two.  .004 is the thickness of a sheet of copier paper.

"As for the spiral marks on the case, I’d have to see a pic."

This


Posting pics... At the bottom of your "Reply" there is a "Attach Image" link...

Click Attach Image, then "Select File".. that will allow a upload from your computer. After selecting your Pic, press upload.

Otherwise select the rectangle ( two mountain peaks and a sun ) next to the link button in the reply top area... insert your cut and paste link.

IM sent

4570govt's photos

One thing I noticed about the cases... the edge / radius at the back side of the barrels chamber could stand some smoothing out. Just enough to allow a smooth transition.

I usually use a over sized shotgun bore mop ( can't fit into the 6.5CM chamber ) and some polish on the front of the bore mop, spun on a section of cleaning rod via a cordless drill.  

Be sure to remove any excess polish and the fuzz PRIOR to closing the BCG into the barrels RE / locking lugs... that lint / fuzz can lock up the bolts lugs and the RE lugs.

Need to see photo's of the chamber entry and to know if you did use a chamber brush with CLP to first clean the chamber before the rig was put into play.

It appears that the back edge of the chamber straight wall section( after the entry raduis chamfer to the straight wall section )is too sharp, and what is causing all the burs to the case on feeding.  Hence once chamber is final reamed, then the chamfer is produced to be a raduis entry into the chamber, not just a counter sink type tool that has the entry just straight walled into the chamber/leaving the end of taper to straight wall section with a sharp or bur'd edge line.

If this came as a built upper, then send the upper back to the manufacturer to have them resolve the problem.  I

If you built the upper, then easy enough to pull the barrel, and do some hand polishing of the chamber entry in a lathe instead.



Simply, chamber chamfer shape should look like this,


No this with the sharp edge at the chamber straight wall section.