Ejector stringing by the clock

[bergermeister]

Will someone please explain the variations of ejected casings stringing between 2-5 O'clock with particular loading and bullet weights?
Thanks kindly

 

[webfarmer]

I can't but can say mine follows that same variation. Handloads or commercial, the same thing happens. Shoots accurately but I find it odd the brass ejects differently - shot to shot. Could be the brass deflector?

 

[Gun pup]

Brass ejected forward (2 o'clock) is a result of excess gas, and the further back it goes the lower the gas pressure. That is a general statement.

Several things can change the brass pattern other than gas- namely buffer spring strength, buffer weight, and BCG weight. It is completely normal for an AR to eject different ammo types at different "clock patterns", since the only thing changing is gas pressure of the round.

 

[bergermeister]

More Technical Please..

Brass ejected forward (2 o'clock) is a result of excess gas, and the further back it goes the lower the gas pressure. That is a general statement.

That is along the line that I was fishing.
I think I read somewhere that the pressure curve (particular powder characteristics and/or charge variations) has a direct bearing on what occurs from the 'Rocking around the Clock'.

 

[webfarmer]

That is along the line that I was fishing.
I think I read somewhere that the pressure curve (particular powder characteristics and/or charge variations) has a direct bearing on what occurs from the 'Rocking around the Clock'.

Yet mine ejects to varying angles from the same load. Recent handload chrono session = 2,693 AVERAGE FPS / ES = 21 / SD = 8 (based on 15 rounds). I can certainly understand ammo differences but not from the same load. Mine is hard on the rims too.

 

[bergermeister]

Mmmm

Yet mine ejects to varying angles from the same load. Recent handload chrono session = 2,693 AVERAGE FPS / ES = 21 / SD = 8 (based on 15 rounds). I can certainly understand ammo differences but not from the same load. Mine is hard on the rims too.

Try backing off about 150fps and see if that doesn't help the case rim problem. A NECO program plots an excessive pressure jump for a small gain in velocity. For a skinny-barreled carbine I would think 2500-2550 fps should be sufficient for ranges it is being used accurately?

 

[webfarmer]

Try backing off about 150fps and see if that doesn't help the case rim problem. A NECO program plots an excessive pressure jump for a small gain in velocity. For a skinny-barreled carbine I would think 2500-2550 fps should be sufficient for ranges it is being used accurately?

Actually, I worked up to that velocity from 2,515 FPS looking for the best accuracy and zero FTE's with rim damage along the way (LC brass). I keep thinking it's the ejector but can't see anything obvious when it's removed. My M&P 15 doesn't do it. By the fourth reload, I've had to replace 20 cases as the gouges wouldn't allow them to fit the Wilson headspace gauge. Oh well - I really like this rifle and hope the problem goes away with more round count (at 440 right now). Good luck!