So today I took my Grendel out and was trying some new 129 gr Nosler loads.  I was beginning to think it didnt like the Noslers so I shot a batch of 123 eld which it loves.

Except not today.  I can usually squeeze insane groups out of them, and today it was 2-3".

I start looking at the handguard and i see it has started contacting the low profile block.

I have been shooting this build about 6 months, never had any problems, and have 2 other MI tubes that havent done this.

I do use a bipod, and wonder if that is causing pressure.  Anyone else have any thoughts, ideas experiences?

Man, I was real concerned about that small diameter handguard. I have the same rail on a 223 build and 300 blackout pistol. I'm not real sure if the barrel harmonics cause contact with the gas block, but it damn sure is a tight fit. It hasn't affected my shooting as of yet, but it was a concern as well.