0.87"ish behind gas block, 0.63"ish ahead of gas block.
Basically your C8 Heavy barrel without the sleeve installed lol
That's what I thought but have never had one in hand to confirm.
I always find it interesting to hear about the concerns of the Colt/Colt Canada IUR configuration because you can't swap barrels. How many people are actually swapping barrels out there regularly? If you make too big of a change your handguard wont work, there are very few people that would ever shoot out a barrel and need to have it changed and Colt Canada barrels are about the best there is for an AR platform (not including precision rigs or if you are building a light weight upper) so is this much to do about nothing? Most people don't have the training, tools or care to swap out a barrel and would go to their local gun smith.
I'm thinking about all the people I've met over the years and they mostly talk about building a new upper to have something different, not just "hey I'm sick of this barrel, I'm going home to change it" lol.
I collect Colt and Colt Canada/Diemaco and for someone that doesn't care about the brand and is looking for a 16" barreled firearm I would point them to a government contour, carbine length gas system barrel, mlok rail by a quality manufacturer. BCM, DD, Noveske etc, etc.
And if you do like the quality and heritage of a tried and true brand that will never fail you and may not be the shiniest, lightest latest tech thing out there but what you can always count on buy Colt Canada.

Oh and forgot one last thing; engineered, tested, designed, built by Canadians for Canadians then of course. Hey, Trump is pro U.S why can't we be pro Canada!