M&P 10 trouble shooting question

[AsheMtnMan]

I replaced the factory M&P 10 hand guard with a MI free float rail and low profile gas block. When I shoot the rifle the bolt doesn't cycle. The rifle shoots just fine as a single shot but something is preventing the gas from operating the bolt. I've checked the gas tube and there are no obstructions. The gas block is aligned correctly. The charging handle lines up with the gas tube. What other trouble shooting can or should I do before reassembling the original factory configuration? Thanks

 

[JBoyette]

Take off the gas block.

Mesure the shoulder to the gas port edge on the barrel.

Then mesure the same section on the gas block

You might need a shim

 

[AsheMtnMan]

I'll give that a try. Thanks

 

[Short Fuse]

Also make sure the new barrel nut is not touching the gas tube and moving it off center.

 

[AsheMtnMan]

It turned out to be just what John said. A shim helped to align the hole in the gas block with the hole in the barrel