This past weekend I was finally able to shoot my 556K after the long wait.  I noticed something strange with the ejection of both of my AR's when running suppressed.  The casings were being ejected between 1 and 2 o'clock, however as I shot through each 10 round magazine, the ejection distance would decrease.  Eventually after about 5 rounds the casings were landing on the bench a few feet from the rifle.  The ejection pattern obviously indicates plenty of gas (I'm running non-adjustable gas blocks) but the ejection distance was strange to me. The ammo was 55gr Federal .223, 55gr Independance M193 5.56, and 55gr Hornady .223.  Does this sound normal?

Rifle 1: 12.5" BCM with H2 buffer and JP extra power carbine spring (I have a softer Tubb Precision flatwire buffer spring I could try)
Rifle 2: 16" Midlength BCM with H2 buffer and standard spring

Can't speak to your issue unfortunately.  I am curious to know how you like the can?  Sound, gas to the face ?  I've got one in waiting...

I am curious about the ejection patterns. Was it the same with subsequent magazines in each rifle?

On the Specwar 5.56K, that is a very nice suppressor. Congrats to both of you.

JPK

I would venture to guess that it has to do with the amount of residual gas in the suppressor after firing.

I only put around 80 rounds through it but I'm very happy with the purchase.  Gas to the face was non-existent, although I'm also running two PRI Gas Busters in both rifles.  Sound was noticeably louder on the SBR but not by much.  POI shift was about 1.5" low @ 50 yards on the 12.5", and the 16" had zero POI shift.  Heck the 16" shot a quarter sized hole at 50 yards with 5 rounds of Hornady Match.  I was very impressed by that grouping.


I just went back and reviewed a few videos we took at the range.  Ejection patterns look very consistent for both rifles.  They start at 2:00 and creep towards 1:30 as the rounds go by.  I don't recall this changing with different magazines.


So this would increase the gas making it's way back towards the bolt?  Sorry, but I'm not sure how that would affect ejection patterns and distance as this is my first suppressor.

This was my initial thought.
I would suggest that although the brass distance changed, they are being ejected to the same general area as stated in OP.
This doesn't seem to compute to scenario where excess gas is present.
Maybe I am just not thinking properly.

Thaddeus,

Gas pressure in the suppressor and barrel will cause more gas to flow through the gas port. That is why a rifle properly set up for u suppressed shooting will be over gassed suppressed. The particular issue here is that ejection pattern moves from 2:00 to 1:00 or so, indicating increased gas as you shoot through your magazine. I haven't noticed it with my suppressed rifles, but maybe it's happening.

But why the rounds are ejecting closer, I don't know.

JPK

I just ran a SpecWar 556 K on my 11.5" BCM upper yesterday and had a similar experience. My lower has an A5 buffer tube with A5H2 buffer installed and I was running a Gemtech SBC. While set on the "suppressed" setting, ejection was 1:30-2:00 and landed about 3 feet away. When I switched the carrier over to "unsuppressed" the casings barely cleared the ejection port and landed at my feet. Ammo used was dept. issue LC 5.56 M193. Has me kinda stumped as I would have expected better a ejection pattern with the SBC in place in addition to the A5 buffer setup...

I have watched videos of full auto with 30rd mags and the ejection goes forward as the mag empties.  It was explained that the full mag creates more drag to get the rounds out. As the mag empties BCG velocity increases.

Maybe this is happening with your 10rd mags?

Makes sense and reminds me I should check my AGB with a full mag to check function after its set to lock on an empty mag.