Quick question for y'all,

I just finished a build and noticed that it is throwing the spent casings quite a bit further then my other AR.   

-- My older AR is a M&P-15 (16" barrel w/carbine length gas system and, I think, a standard buffer weight) and "dribbles" the casings off the defector in the 1-2 o'clock direction 4 feet or so. 

-- My new build is a Spikes upper (14.5" barrel w/comp and mid length gas and an H-buffer) and throws the casings in the 4-5 o'clock direction a good 7-10 feet when sitting.

 

Is this something I should be concerned about.. or a sign that I miss-configured something during the build?  The M&P feels like it has more kick when I shoot it compared with the Spikes, as I'd expect.. so I'm surprised the casings are going out so far.

 

Thoughts?

Look at extractor spring tension.  If you have an extra power extractor spring or an o-ring installed in one bolt but not the other, expect brass to fly further.

 

Ideal ejection is 3-4 o'clock.  Your M&P is exhibiting signs of being overgassed

 

that purple/pink part is hilarious

Also, try swapping the action springs or the entire upper and see if that reverses the issue between the guns.

 

Sounds to me like your Spikes rifle may be good and the M&P may be having the issue.

For the spikes, I was primarily concerned by the distance it was throwing the casings.. Seemed excessive. The direction was right based on above.

 

For the M&P, what am I looking for? Why does over gassing result in that behavior? What I found odd was that the casings were ejecting at noticeably less velocity and only going 4'ish feet. Definitely in the overgass direction on the chart above.

Swap out your carbine buffer with an H1, H2 and go up the line until you find one that works for you.

So I pulled the bolts out of both rifles last night and took out the extractor on both.   I couldn't tell much of a difference between them other then there was some grime under the M&P extractor "lip".  Could that have caused the above issue?  The two springs looked identical as far as I could tell.  Either way I cleaned it out and will keep an eye open at the next range trip.

 

Note:  The M&P was ejecting in the right direction and it wasn't until this last range trip that I noticed it ejecting forward.  This makes me think its not a buffer weight issue.  Otherwise the behavior would have been there all along, right?

Extractor Spring Kit - 3 pack.

Good to have on hand next time you order from BCM or source yourself.  I also keep a firing pin or two on hand.

 

http://www.bravocompanyusa.com/BCM-Extractor-Spring-Uprade-Kit-p/bcm%20extractor%20spring%20%203pack.htm

Man, if you can tell the difference between 4:30 and 5:00 on ejection you've got better eyes than I do!

For the spikes, I was primarily concerned by the distance it was throwing the casings.. Seemed excessive. The direction was right based on above.

 

 

My Bushmaster Carbine with a 14.5 barrel shoots 7-10 feet at the "proper" angle.   I know that carbines cycle a bit harder, so that may account for the additional range of the ejection.

 

A heavier buffer will reduce this if you're worried about it.  I wouldn't be.

My Bushmaster Carbine with a 14.5 barrel shoots 7-10 feet at the "proper" angle.   I know that carbines cycle a bit harder, so that may account for the additional range of the ejection.

 

A heavier buffer will reduce this if you're worried about it.  I wouldn't be.

Thanks.

For the spikes, I was primarily concerned by the distance it was throwing the casings.. Seemed excessive. The direction was right based on above.

 

For the M&P, what am I looking for? Why does over gassing result in that behavior? What I found odd was that the casings were ejecting at noticeably less velocity and only going 4'ish feet. Definitely in the overgass direction on the chart above.

 

All your brass hits the brass deflector. Where it lands is largely based on how hard it hits the deflector and at what angle. The angle is largely determined by how much flip is imparted before it hits by the extractor and ejector. How much flip is largely dependent on how fast it is cycling, which is dependent on how much gas the gas system is getting vs. how light or heavy the total mass of the BCG and buffer are. 

 

Undergas, and the brass has less velocity overall and the BCG moves slower and thus the brass flips early (farther forward). It either misses the deflector entirely, or it rolls up it like a ramp due to low energy. Just right and it mostly hits part of the deflector that is square to the ejection port mostly on the side, and bounces to the side getting it's direction from sort of pivoting around the 45 degree wedge. Too much gas, and it flips late (further back), and it mostly flips the brass into the 45 degree portion of the brass deflector, which bounces it straight forward. 

 

Weird ejection patterns can crop up because of non standard deflector shape, going with a lightened buffer and carrier with adjustable gas, ammunition choice and pressure thereof, or a number of other things. It really doesn't matter unless you have other issues to go with, or if the ejection pattern is causing you ergonomicv issues like hitting you and distracting you or burning you, getting in the way of your vision, etc. The chart midwestPX posted is a diagnostic tool to assist with diagnosing actual problems. Where your brass goes isn't a problem in and of itself IMO as long as it runs reliably in all temps with a wide variety of ammo. 

 

I have a carbine length gun I put an adjustable gas block on. Wolf in the winter barely operates the gun. xm193 in the summer heat makes the recoil a lot more harsh. Where the brass goes varies GREATLY between those two scenarios, but guess what. The gun is pretty solid because it doesn't short stroke wolf in the middle of winter, and doesn't fail to strip rounds off the magazine shooting xm193 in the summer, and it can happily chew through 1000 rounds of dirty ammo without cleaning and still run. There's nothing wrong with the gun despite brass piling up in different spots. 

 

Here's normal (about 12 seconds in) :

 

Here's normal from a /34 vertical view: 

 

Here's a perfectly fine rifle likely operating with a lightened carrier and buffer. His rifle appears to be set up for a bit of extra BCG velocity for reliable extraction and he's mostly getting benefit form the low mass carrier system by having less mass slamming forward thus causing less sight dip, adn letting the comp and technique deal with any muzzle rise form the increased BCG velocity. Especially the footage form the side shows the behavior that send the cases forward to the 2 oclock area. (slow mo starts at 47 seconds):

At national matches, I have seen the mat side of velco glued to the shell deflector to slow down the brass.