Earlier this year I wrote a post on the URG-I upgrade kit for USASOC’s M4s. This is a pretty simple set of drop-in parts to improve the functionality of the M4 by using a low-profile gas block, barrel with a midlength gas system, improved flash hider that can also mount a suppressor, and a new, longer, free-float handguard with mlok slots instead of picatinny rails.

When I first wrote the article, I compared it to a “stock” M4 upper. To do so I had to make some guesses as to the weights of the new parts. I have since been able to find the correct weights, and the article has been updated with those.

If you just want the correct weights without re-reading the article, they are as follows:
Geissele Mk 16 13″ handguard, 14.7 oz.
Surefire SF4P flash hider, 4.48 oz.
Daniel Defense 14.5″ CHF Midlength, Gov’t profile barrel, 24 oz.