I am interested in putting together a 16" barrelled flat top upper from BM. I want to use the handgaurds from the new Les Baer Thunder Ranch carbine featured in this October's issue of Guns Magazine. I also intend to use Les Baer's new flip up front site/gas block featured in the same article. My questions are as follows:

Will the parts from Les Baer's floater tube carbine handguard be compatible with  BM's barrel? Are the uppers that come from the major suppliers made with the same dimensions, tolerances, threads, etc. to facilitate parts swapping like this?

If I use LB's front site/ gas block will I be able to use a gas tube for a 16" barrel from BM or might the length of the gas tube be different when using LB's front site rig?

Thank you

Well, these things are supposed to all be made to the same spec, but in reality there is some variation.

The only thing I'd say is get the parts from a good vendor, so you won't wind up with somebody's rejects. That matters most with the parts that have the finest tolerances, but with something like handguards there's a lot of wiggle room, so to speak.

I personally get all my parts from the same vendor when building a rifle, that just ensures that everything will fit. But if you're on a budget, just try to make sure the bolt and barrel come from the same place, just a good idea to try and head off any problems with headspace. I've seen uppers/lower from different mfgrs not matching up exactly right (DPMS lower, in my case).