I have a 10.5" SBR that wont lock the bolt on the last round (with any magazine).  The gun runs great with no feeding or ejection issues.  I have never shot any other SBR's in the past so I don't have any comparisons in those regards but compared to other 14.5 or 16" carbine length AR's it seems to have noticeably more recoil.  Brass is being ejected at a strong 2ok position and I have tried both a standard carbine and H2 buffer with the standard carbine spring only.  Neither seemed to make a difference in operation, ejection or recoil.  

I'm running a BCM full auto carrier, Noveske 10.5" barrel with A2 front sight (supplied with barrel) and standard carbine buffer spring.  The bolt locks back manually and all components look and feel to be in proper order such as gas key, rings etc.  I have only shot it using federal XM193 and the Brass looks good, no bulging, no ripping at the rim, no real dings or marks in the side of the case.  A couple cases had very small dings but nothing that I would call unusual strike marks from hitting the brass deflector.  

So, whats my issue?  I'm thinking an over gas due to the direction of ejection and recoil.  However seeing that I'm running a heavier BCG and H2 buffer I'm surprised especially considering there's such short section of barrel after the gas block; I would expect the opposite from an SBR.   So does Noveske usually run a larger than normal gas port to compensate for the short barrel.  Is greater recoil normal for an SBR?  

I don't want to change to an adjustable gas block and Id rather not spend the $$$ on an adjustable BGC if that isn't the issue, that's a lot of money for "just trying something".  Seeing I don't have much SBR experience id love some feedback.  Thanks!

I'd suggest playing with your buffer weights. You can just buy some tungsten and steel weights if you don't want to but multiple buffers but its a good investment to have a few of different weights laying around.

May need an H3 or may even try a standard buffer.

1) Just be clear, please confirm that the bolt locks open on an empty magazine (as opposed to you manually actuating the bolt catch).
2) What magazines are you using?
3) What is the ejection pattern - is the gun throwing brass forwards, sideways or backwards?

You could be overgassed OR undergassed. If you can get some slow-motion video it might help you.

strong 2ok position, multiple magpul p-mags, the bolt locks back when the bolt is manually manipulated on an empty magazine OR when the bolt catch is manually manipulated without a magizine.  The bolt does NOT lock back after the last round is fired as it should.  After the last round is fired the bolt then closes on the empty magazine.

I'm thinking its over gassed but I'm surprised seeing its a 10.5 barrel with the weight of a full auto carrier and H2 buffer.  

Also, to be clear, I'm not concerned with the angle of ejection and only used it to reference the total picture.  As far as I'm concerned, two OK is fine if the rifle functions as it should.  In my opinion and generally speaking, slightly over gassed is better than under gassed.  Like I said my 14.5 factory built Noveske tosses brass at 2ok too, but that is on smooth shooting rifle.  The SBR isn't violent but its a stout recoil as ARs go.

The recoil, ejection and bolt not locking back spell over gassed.

A Gemtech or Bootleg adjustable carrier is the best fix if you want to keep the A2 front sight.

A heavier buffer for a bandaid on the cheap.

You are over-gassed.

-Heavy buffer
-Adjustable gas block, gas key, or bolt carrier
-New barrel

In that order.  There is some baggage with each of those solutions, so read up.

Just ordered an H3 buffer. I don't think it's going to be enough but its the cheapest so I'll start there.

H3 buffer and Blue SpringCo spring.   VLTOR A5 system.  Bootleg adjustable Carrier.  Adjustable gas block.   Done all of those for various SBR uppers/lowers. The adjustable gas block is a sure thing.  The VLTOR A5 system is definitely more forgiving and has pretty much worked with everything I've slapped on that lower. The Bootleg BC turned a fail to lock back (suppresssed) upper into 100% reliable.   The H3 and stronger spring works if it's a slight problem.

Contrary to previous opinions, my initial suspect would be insufficient gas delivery to the bolt carrier. With the shorter barrel, pressure delivery through the gas tube drops faster, reducing the rearward force on the carrier assembly. Sounds like it is consistently driven back far enough to extract, eject, & strip a new round from the magazine, but not quite far enough to permit the bolt catch to rise in front of the carrier. Enlarging the gas hole in the barrel by a couple thousandths should do the trick, once you've confirmed everything is assembled correctly & free from clogged debris.

I disagree with the above. Get a standard carbine buffer (which is dirt cheap since so many people needlessly swap them out) and see if it runs with that. I bet it will.

I have 3 SBR ARs along with two pistols. Every single one has a standard carbine buffer. Every single one functions flawlessly.