My SBR has been really reliable up until recently.. 

I just changed the gas block so I suspect it is possible that the port is just not lined up correctly but here is the condition.

* Gun will fire
* Spent case may not fully clear the port 
* Next round does get stripped off of the mag and loaded
* sometimes ejection is so weak that the spent case falls back into port causing a jam

This condition occurs erratically several times per mag, and appears to happen more regularly with a higher rate of fire.

I checked gas block alignment but what else should I be looking at.

Leak at the gas tube to gas block connection or the gas rings are shot.

Check ejector spring .

Why did you change the gas block. ? 

+1.

Btw, is this gas block by any chance adjustable?  If so... you just may need to open it up.

In what direction is the brass being tossed?

OK so the wife came to the range.. a few observations... 

• The only change prior to shooting was an increase to a slightly heavier buffer
• Ejection improved significantly
• Ejection is CRAZY far forward, like 1:00 forward

 

I am going to make some assumptions

• The heavier buffer increasing reliability
• The extreme forward ejection
• The fact that I just swapped out a really questionable gas block for one that appears to be decent quality 2A Armament Ti block

The gun is likely overpassed. This condition may have been created by ditching the previous block, maybe the port was undersized? Maybe it was not properly aligned who knows.... 

My next steps are:

• Heavier buffer
• BCM Extractor kit just for good measure (this spring has definitely seen thousands of rounds) 

2 hours ago, silverado427 said:

Leak at the gas tube to gas block connection or the gas rings are shot.

Check ejector spring .

Why did you change the gas block. ? 

the old one was really a POS and starting to leak gas between the block and the barrel under heavy sustained fire.. 

its funny how first instinct is not always right.. when I saw the spent case in the port I assumed the ejection was super weak.. but I think its actually the opposite.. I think the ejection is so aggressive that the spent case may be getting knocked around in there because the action is so violent.. 

The ejection chart is super helpful and I think it actually makes sense now.. 
I think the new block for whatever reason is simply letting in more gas than the previous one... 

2 hours ago, Maksim said:

+1.

Btw, is this gas block by any chance adjustable?  If so... you just may need to open it up.

In what direction is the brass being tossed?

negative not adjustable... a small increase in weight of the buffer added a ton of reliability compared to yesterday.. so I am hoping I can solve this with a heavier buffer..