Okay, I just tried to install my new Magpul MAG426 forend on my M&P10 and, although it appears to fit perfectly in length, the barrel nut seems to be too big (diameter) for the grips, which makes it impossible (for me) to get the D-ring over the rear flange of the grip. All other dimensions appear perfect. Anybody know what I'm doing wrong? Has anyone else experienced this and overcome it?

(By the way, the S&W catalog for the M&P10 indicates that the MAG418 is a fit for the rifle. The MAG426 that I'm using is the updated M-lok version of the same forend.)

Magpuls are really tight on these. Typacally if you will get both sides started, slapping them or use of a rubber mallot will get it done!. You could sand the ends a bit if you just must.

copemech, thanks for the feedback. I was trying not to get too physical with it the first attempt as I was a bit concerned of damaging the gas tube. Will try a bit harder today. I may do a bit of sanding/trimming on the hand guard cap end to get it to fit at the barrel nut.

I believe a few others had to do some strategic sanding on theirs to get them to fit. They are a tight fit. I had to help the armorer install mine. I pulled on the Delta ring while he fought the pieces into place.

Thanks for the info. I think I need an armorer's help too! I did a little more "strategic sanding" but still no joy. The barrel nut is simply too far forward (toward the muzzle end) for the rear of the forend to fit over it. I think I'd have to remove nearly all the internal flange material from the grip to get it to fit. On top of that, the barrel nut itself seems to be too large in diameter to get both pieces of the forend to fit over it. Not giving up though. I'll keep working on it until it either fits or I've destroyed it. The new forend, that is...

If memory serves, he inserted the barrel/Delta ring side in first and closed the halves together at the gas block end.