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Hamms
03-09-15, 00:13
I am seeing very different brass swipes on the brass deflector between two rifles. One is a DI BCM, the other is a factory Adams Arms type piston system.

Both are 16" midlength, M16 profile BCG's, standard extractor spring without o-ring, H1 buffer with standard carbine spring, and ALG triggers. Only difference between the two is DI and piston. Both run 100% on M193, Q3131, PMC bronze, and WWB 5.56 and both eject about 3 or 4 o,clock. I'm getting random dings in the case walls and case mouths.

I'm not concerned about the marks themselves, but rather what they might be indicating about the ejection. Do these indicate a problem with early or late ejection (BCG speed too fast/slow, extractor tension, buffer weight) or should I just rock on???

BCM deflector:

http://s25.postimg.org/ijf9s2r1b/bcm_deflector.jpg

AA deflector:

http://s25.postimg.org/nw4467exr/AA_deflector.jpg
Iraqgunz
03-09-15, 01:37
Different ammo is one issue. Q3131 is hot and I have seen it blow primers (and it wasn't the weapon). In addition you are running a piston and pistons are generally overgassed in order to move the mass of the operating rod. I would be surprised to learn it wouldn't cycle with and H2 or 3.
markm
03-09-15, 08:22
or should I just rock on???


This!!
Hamms
03-09-15, 14:45
Different ammo is one issue. Q3131 is hot and I have seen it blow primers (and it wasn't the weapon). In addition you are running a piston and pistons are generally overgassed in order to move the mass of the operating rod. I would be surprised to learn it would cycle with and H2 or 3.

So on the AA I should try an H2 or H3?
Iraqgunz
03-09-15, 15:55
I cannot say for sure. Trial and Error is sometimes required.


So on the AA I should try an H2 or H3?
HKGuns
03-09-15, 16:03
Only difference between the two is DI and piston.

Pretty huge difference right there. Rock on and try different buffers if you want, experimentation is your friend.
crazymoose
03-09-15, 19:12
It might well be that the piston setup looks different running optimally than a DI gun. Believe AA recommends standard CAR buffer. That said, no reason not to experiment, especially if you shoot non-crap ammo. While I do think AA is pretty on the ball as far as piston companies go, I suspect they know a lot of their customer base is the bump fire/berm shooting variety, and engineer their stuff to operate with crap ammo.
ezveedub
03-09-15, 22:11
I run the Adam Arms mid gas system along with DI mid and carbine. I use a Spikes T2 buffer in all systems and took the carbine buffer out of the AA rifle and actually switched it to a Spikes T3 over the T2 buffer. Never really had any ejection concerns, but recoil felt was harder with a T2 spikes compared to a DI mid with the same T2 buffer.
redmist
03-09-15, 22:17
Top one looks like my test rifle right now... I was wondering the same thing. I see a perfect 3:00 ejection from this gun, but it leaves the same sort of marks on my deflector. This was 1000 rounds even of Q3131 (I had one blown primer in the batch) Brass looks just fine though. No dents or anything.

https://scontent-sea.xx.fbcdn.net/hphotos-xpf1/v/t1.0-9/10941519_892835187403978_906799893285144620_n.jpg?oh=a16ca9fdd71be7e351ec9a002367bcd7&oe=558D004E
DirtDiver06
03-10-15, 00:04
Dude seriously... this is arfcom shit
MistWolf
03-10-15, 07:03
Clearly, you're getting more violent ejection from this rifle
http://s25.postimg.org/nw4467exr/AA_deflector.jpg
Hamms
03-10-15, 14:14
Dude seriously... this is arfcom shit

I'd rather my rifles run "perfect" than just "ok". Arfcom is full of high school B.S. so this is the better place to get informed feedback.


redmist

Top one looks like my test rifle right now... I was wondering the same thing. I see a perfect 3:00 ejection from this gun, but it leaves the same sort of marks on my deflector. This was 1000 rounds even of Q3131 (I had one blown primer in the batch) Brass looks just fine though. No dents or anything.


I viewed slow motion videos of DI and GP ejection and my BCM and your rifle look to be the typical pattern; case contacting the deflector after turning 90 degrees. I found one video of a PWS that exhibits the same impacts as the AA and it appears that the BCG is cycling slower allowing the case to spin around 180 degrees before contacting the deflector. This tells me that the AA is cycling slower than the BCM, so I need to step down to a carbine buffer to avoid short stroking on weaker ammo, not up to an H2 or H3. I suspect the smaller surface area in the AA piston transmits less force than the piston in the BCM BCG.
mtdawg169
03-10-15, 15:16
I'd rather my rifles run "perfect" than just "ok". Arfcom is full of high school B.S. so this is the better place to get informed feedback.




I viewed slow motion videos of DI and GP ejection and my BCM and your rifle look to be the typical pattern; case contacting the deflector after turning 90 degrees. I found one video of a PWS that exhibits the same impacts as the AA and it appears that the BCG is cycling slower allowing the case to spin around 180 degrees before contacting the deflector. This tells me that the AA is cycling slower than the BCM, so I need to step down to a carbine buffer to avoid short stroking on weaker ammo, not up to an H2 or H3. I suspect the smaller surface area in the AA piston transmits less force than the piston in the BCM BCG.
Don't step down in buffer weight unless you've verified an issue with short stroking by actually firing the gun with whatever weak ammo you deem appropriate. PMC bronze is already pretty weak and you said it cycles fine.