Originally Posted By: ninehorsesSome of this comes from trying to get the right pressure for reliable ejection. In a perfect world, your AR should toss the brass out from 3:00 o'clock to 4:30, from 3:00 o'clock forward you are over gassed, 4:30 - 6:00 you are short stroking or under gassed. This assumes you have the right buffer, spring, carrier...
Many AR's are 9 -7 twist, most of the AR data is for the longer heavy bullets, and the chamber-throat that are designed for them.
I wish Catshooter was still around, he could make some interesting post on pressure in the .223 - 5.56 debate. This would come up about every two weeks. Feel free to do a search if you are interested in some lively debate. Be sure to bring popcorn!
tbh- i believe thats one of the biggest differences in 223 data out there. a 223 chamber, vs a 223 wylde, vs a 5.56 are entirely different animals when it comes to the throat/leade area. attempting to use many of the heavier for caliber bullets from the "service rifle" or 5.56 load data in a standard 223 sporting chamber with its relatively short throat/leade could easily end up with a bullet being jammed into the lands and having an over-pressure safety issue.
which is why unless you specifically custom order a barrel, most production ar's these days that are listed as 223/5.56 are actually WYLDE chambers, and not standard 223 rem chambers.
i dont disagree with your tuning for proper ejection stuff so much, although i feel thats something that moreso needs to be done either at the gas port via an AGB (adjustable gas block) or in the receiver extension with buffer weight adjustment. doing so by lowering the charge of your reloads works, but you're needlessly sacrificing velocity to modify something that can be handled elsewhere safely and reliably.
Just like the safety factor of cutting WYLDE chambers instead of standard 223, many manufacturers intentionally over-gas their guns to ensure reliability with either sub-par steel case ammo, or for circumstances where maintenance cleanings are neglected well beyond normal. So they'll run that 16" carbine gas barrel with a 3oz buffer to make sure the gun runs - even if its throwing the brass in places it shouldn't be in ideal circumstances or bottoming out the buffer in the buffer extension.
just so that some bubba can go "bang-bang-bang" and then just stuff their gun in the safe until next time without worrying about it cycling due to a mostly dirty and unmaintained bcg and not complain online how "their gun sucks" when its not the guns fault at all
in a perfect world, on that 16" 223/556 barrel... mid-gas and a h2 (4.5oz) buffer is probably a better option, but will require the user to maintain their gun better top achieve the same reliability that adding port pressure by using the carbine gas port position gives.