New BCM rail

[jerrysimons]

@ESK

Yep, you are correct. Some of those mentioned comps have excessive expansion chambers, which trick the weapon into thinking it has a 2", 3" and 4+" longer barrel after the gas port. That’s the beauty about the AR platform, at least we can balance it out by adding more reciprocating mass, i.e. the A5 buffer system.

@ESK

As I see it, you kinda have to work around what’s offered to you, meaning the barrels are a set specifications from the manufacturer. It’s not to often we can have a barrel made to our specifications. So, I usually work with what I have. There are many of time I’ve chopped barrels down, because A) the gas port is too big and B) there’s too much barrel after the gas port. I only install a expansion chamber type Comp/FH when the barrel is to short after the gas port. I like to run just FHs or non-expansion chambers Comps when running a proper length barrel. My biggest pet peeve with ventilated expansion chambers is the occasional fireball they produce every few rounds. I like my flash (or lack there of) as consistent as possible. The rest of the formula is working on adding or subtracting reciprocating mass, keeping it balanced around ammunition types.

Every once in a while a post blows your mind…
Could this be a mystery variable as to why some barrel-length/gas-system/buffer-weight setups seem to defy the conventions of what should cycle?

Which devices have expansion chambers and which do not? How do we quantify them?
As much as we obsess about buffers, gas length, barrel length, gas ports and even LMT enhanced carriers, how have we over looked this aspect of “tuning”?