Need some help diagnosing my Grendel

[strike33]

Bought a Larue Grendel, rifle functioned fine but I was a little disappointed with the accuracy. I got with Craddock and had an 18" SPR profile barrel spun up and coated FDE.
I initially installed a Superlative Arms gas block. Problem is the gun won't cycle/ feed correctly. It will fire, extract and charge the rifle but it wouldn't pick up a new round (possibly short stroking?). I tried playing with the gas but it would go from not cycling to be over gassed and stove piping without it properly cycling in between.
I thought maybe it was an issue with the gas block so I switched it out with a POF Dictator. Same issues.
The barrel is pretty accurate but I can't get this thing to function. I put the factory back in several times and it functions just fine (with the lack of accuracy). I've put the upper on several other lowers to see if maybe there was a mag seating issue but still a no go.
I did chat with Paul Craddock and they are willing to take it back and check it over and see what's going. Just trying to see if there is something else I can try before shipping it back.
Much Appreciated

 

[XLR308]

A low mass carrier and buffer would allow you much more flexibility for tuning your gas system.

 

[strike33]

I'm running a JP full mass and bolt, I've tried my JP captured spring with no luck. Its just killing me that the factory barrel with the non adjustable block works fine but I can't get this Bartlein blank to work. I asked Craddock if it was possible that some Cerakote got into the port and they said not likely but possible. Their solution was to take it back and open up the port, but I don't want to deal with an oversized port either.
I do appreciate the response.

 

[XLR308]

Thats strange it would go from not cylcling to over gassed.
I've had one AR that appeared to be short stroking but it was in fact over gassed, the timing and pressure curve were just right at that point that it wasn't releasing from the chamber wall as it was trying to unlock.
Did you inspect the chamber really well to see if there was any overspray from the cerakote in it ?

 

[strike33]

Chamber looks good. I haven't been able to have someone else watch or fire it so I could try and see what the carrier was doing as it cycles.
I'm ordering a JP detent adjustable gas block to replace the POF as I don't like the clearance. That's going to be the last thing I buy before I replace the barrel altogether while I send it back to Craddock.