My limited knowledge indicates it shouldn't for safety reason, .338 bullet in to a .30 cal can. But I don't know what the tolerances in that can are. Haven't received mine yet. Following waiting for someone who actually knows the answer to answer.
Yes I understand but I believe they try to idiot proof this stuff so mistakes are not made. Thus they would make the muzzle break QD for a .338 so that you couldn't attach a 762 can to a .338 but that is just supposition on my part. I see what you mean and you may be right but when I look at the brake for the 762 it doesn't show upward compatibility.
Yes those are the thread patterns they fit. I bought two different muzzle breaks from OSS for my new Helix. One fit .308's and the other fit .556. I assume both had same threads. I guess I could have put one made for a .308 cal on the 556. But both were made for the same can. I guess that is what convince me. Didn't even try to buy one for a .338. I will have to check to see if a suppressor made for a .338 will mount onto my muzzle break. With what your saying it will.
I checked with my OSS dealer, Waymore Silencers out of Houston and the 762 will not thread onto you .338 brake by design, not only due to bullet size but the pressures generated are too strong for that can.