Feeding issues. Doesn't wanna eat.

[Peterjf]

Lube that puppy up...

Lubed before I took it to the range and while I was there. So she's plenty wet.

 

[Peterjf]

Just to add more context to the post, I can seat the mag, pull back the charging handle(smoothly), send the bolt home, it will pick up and chamber the round fine. Fire, eject the case. Case appears to eject at a 4-5 o'clock. Also fails to hold open on the empty mag after last round is fired.

 

[Allsmiles]

Try the upper on another lower and see if it is the upper or lower that is off. One last question, upper is 223 and not 300BO right.

 

[Peterjf]

Try the upper on another lower and see if it is the upper or lower that is off. One last question, upper is 223 and not 300BO right.

Lower has been used with 2 other uppers. Ran fine. Several hundred rounds .223/5.56 on this lower and its been almost flawless. I love the lower for what it is (M&P sport 2) just wanted a different style upper.
And yes its a 5.56 and not 300BO

 

[User170512]

Any pics of spent brass that does eject?

 

[DanKATL]

Just to add more context to the post, I can seat the mag, pull back the charging handle(smoothly), send the bolt home, it will pick up and chamber the round fine. Fire, eject the case. Case appears to eject at a 4-5 o'clock. Also fails to hold open on the empty mag after last round is fired.

That carrier is "semi-cut" which makes it lighter than a standard carrier. You moved from a carbine to mid length gas. Your gas system is a balance of the moving mass (BCG, buffer, etc..), the amount of gas coming back and when it releases combined with the spring. That's out of balance (sounds like too light). There are multiple ways to fix that (spring change, buffer weight change, carrier change, gas port size). Someone like cmshoot could tell you which one is most likely to fix and easiest to fix it.

 

[Peterjf]

Any pics of spent brass that does eject?

Anything I should be looking for one the brass? Dents, scraps, bulges?

 

[Peterjf]

Any pics of spent brass that does eject?

This is what the second rounds look like after the first is fired then ejected. Second round doesn't feed.

 

[Spas-12 Owner]

Try a different weight buffer. H2 or lighter.

Pictures of the buffer?

 

[Blaze]

DanKATL is correct. You can manipulate the bolt manually with no issues because your problem isn't mechanical...it's the gas system. Something is "out of balance". Either it's undergassed or the buffer is too heavy. The bolt isn't going all the way back, therefore not catching the next round (or not properly) and the last round bolt hold open isn't happening because it's also not going back far enough to catch the latch. I would say if you want to swap uppers around like you're doing, get an Odin adjustable buffer and then you could tune it for whatever upper you want at that particular time.