Quote Originally Posted by Deadwing View Post
Man, there are so many variables at work i think it'd be difficult to definitively say a 10.5" will run better suppressed than an 11.5 or vice versa. The additional dwell time of the 11.5 allows chamber pressure to drop a bit more before the round is extracted, allowing for more reliable extraction. But increased dwell time is only good to a certain point. Excessive dwell time can effectively over-gas the gun (this is why mid length gas systems are favored on 16" barrels as opposed to carbine length, not to say that a carbine gas system on a 16" barrel can't be made to function reliably). Adding a can to either a 10.5" or 11.5" barrel will likely result in the gun being overgassed, as the back pressure of the suppressor effectively increases the dwell time (although actual dwell time remains the same in each respective barrel, since the bullet still leaves the bore at the same time it would if shot unsuppressed). Specifics of gas port size, how much back pressure a specific can will add, etc. all play a part. The 11.5 has a higher dwell time than a 10.5, so on paper, with the same can and same relatively sized gas port (i.e. the smallest sized gas port for each barrel that would allow reliable function with nato pressure ammo) in both barrels, the 10.5 would probably be less overgassed than the 11.5. That said, both barrel lengths can be run quite reliably suppressed by running an adjustable gas block, and/or different buffer/spring combos. I don't recall the numbers, but i remember reading that the 10.3" barrels Daniel Defense sells to the general public have a larger gas port than the ones they sell to the military, the logic being that the .mil will always run nato pressure ammo (and frequently run suppressed), where John Q. Public will run everything from Tula .223 to quality 5.56x45 nato. With the smaller gas port of the .mil 10.3, the guy running Tula would find his gun undergassed and have cycling issues. Throw a can on that same gun with the same ammo, and it'd probably cycle fine. Conversely, the commercial spec 10.3" DD barrel will cycle fine with all types of ammo (i've found mine runs best with an H2 buffer using nato pressure ammo), but add a can and you'll probably find you need to run a heavier buffer/spring combo to compensate for the extra pressure in the gas system. Now, on the 11.5" barrel, the gas port could probably be made larger to allow the end user to shoot a variety of different pressure ammo, and the increased dwell time wouldn't make the gun as sensitive to extraction issues associated with an over gassed gun.

I'm no expert, and it's been a while since i stayed in a Holiday Inn Express, so please correct me if my thinking is completely wrong.
I would rather add an adjustable gas block than add a heavier buffer and spring, even though that is the cost effective way. The heavier buffer will slow the carrier speed but you still have a lot of gas dumping out of the ejection port/in your face and you'll have an increased recoil impulse. Having the ability to tune the gas so it runs properly despite the gas port size in the barrel is the way to go.

You are right, the heavier buffer will help compensate for the suppressor, but it causes some other side effects that aren't ideal.