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That just seems to run counter to everything previously known about 223 vs 5.56. back in the days that everyone shot Winchester q3131 it was accepted that 5.56 was a hotter round than 223, now all the sudden they are the same? When did this change? At this point we are only assuming Federal used the longer rifle barrel for testing which I think would be the case but still the velocity for their 223 load seems at least equal if not hotter than 193.
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I think the key words here are “known” and “accepted”. They are often interchangeable in usage (kinda like how you linked them in your post) even though everyone should know better than use them so.
From my understanding, the parameters for measuring velocity aren’t as rigid since SAAMI is worried about safety (mainly pressure). So for velocity, there can be quite a bit of variation in how the company measures it...different rifle actions, barrel lengths, even raw measurement and averaging variations.
Now, imagine how a company that is trying to sell ammo to a public that believes 5.56 is hotter than .223 is going to approach marketing both their 5.56/.223 ammo. Do they want you to only buy 5.56 ammo for your AR? Or do they want you to buy their .223 ammo rather than a competitor’s 5.56 ammo? So for an AR owner, what is going to prompt you be comfortable buying .223?
And to further muddy the waters, they can’t really abandon the .223 label and label everything as 5.56, because then a bunch of bolt gun guys are going to abandon their product line for fear of blowing up their rifles with 5.56 ammo.
But, their lawyers also aren’t telling them they have to put warning labels on 5.56 ammo boxes about using it in .223 rifles, are they?
Just think about all the confusion over the years over .308 and 7.62NATO. I can see ammo makers basically throwing up their hands and trying to work within the buyers’ preconceived notions and prejudices rather than risking sales by trying to clarify and educate the buyers in limited space on product packaging.
Edit: a poster above implies that SAAMI specifies how velocity is measured. My understanding was that they don’t strictly regulate that. So I may be wrong.