Ejection Routes Inconsistent

[tehpwnag3]

Aside from just a smidge of bolt bounce, the operation looked fine in the video. Post a video of it failing. That would be more helpful. Don't be afraid to get the camera really close to the ejection port. Also, if you can string together a few shots (good or bad), it might show us more as well.

[masterdrago]

Aside from just a smidge of bolt bounce, the operation looked fine in the video. Post a video of it failing. That would be more helpful. Don't be afraid to get the camera really close to the ejection port. Also, if you can string together a few shots (good or bad), it might show us more as well.

Rain ran me off today but I'm taking more video tomorrow. I had to crop the original but I got much closer with better lighting but the rain came in.

[Dr. Bullseye]

Looking at your video and not knowing but taking a guess----I would guess the bolt is short stroking because of the heavy buffer. It does not look like the round is being taken off completely by the bolt. People might ask about the mag as it is a feeding issue but this is a Pmag, right?

[masterdrago]

Looking at your video and not knowing but taking a guess----I would guess the bolt is short stroking because of the heavy buffer. It does not look like the round is being taken off completely by the bolt. People might ask about the mag as it is a feeding issue but this is a Pmag, right?

P mags, K mags Crapco mags!! Aluminum, plastic, you name it. Nothing consistent. Ran through a full Gen3 a minute ago with no malfunctions. Made another vid. Really hard using phone since it will only take a .2 second super slo-mo (940fps), then might want to shift focus, then delay and not think anything is detected moving in the sensor square even though the bolt is running full balls. Maybe there is an app for that. My GoPro will shoot nonstop but only at 240fps @720 - not fast enough. Anyway, here it is and I'll keep trying....

[MegademiC]

P mags, K mags Crapco mags!! Aluminum, plastic, you name it. Nothing consistent. Ran through a full Gen3 a minute ago with no malfunctions. Made another vid. Really hard using phone since it will only take a .2 second super slo-mo (940fps), then might want to shift focus, then delay and not think anything is detected moving in the sensor square even though the bolt is running full balls. Maybe there is an app for that. My GoPro will shoot nonstop but only at 240fps @720 - not fast enough. Anyway, here it is and I'll keep trying....

Yea- need slow-motion of the jam. Even at 240fps, you can slow to 1/8 or 1/16 and see whats going on. Last round looked like it ejected weak, but really hard to tell from that vid.

Edit if you have an iphone, take slowmo at 240 and use imovie to slow it down.

[Dr. Bullseye]

Do you have a normal carbine spring, a H1, H2 and H3 buffer or do you add and subtract weights making up your own as I do? I remain curious how it functions with the H1 or H2 buffer and the blue spring.

[masterdrago]

Just to reply to Bullseye, I've configured it with many combinations of buffers, springs, magazines, & various ammo, from light .223 to heavy 5.56. IMI 62gr almost will not chamber at all. Best is 75gr Hornady TAP SBR. It just appears to every once in a while as it runs a fresh cartridge up from the magazine, there is a slight bounce as it exits the mag, causing an odd angle when entering the chamber. As I mentioned in another thread, I plan on taking it to a good armorer and pay to have it fixed when I get time.

[masterdrago]

Yesterday, with my sons' help, I got another video using my cell phone. If you look closely, the 1st shot loads the next round from the far side of the magazine. When the 2nd round is fired, the BCG comes back and picks up the next round from the near side (ejection port side). As it slides the round forward, something gets aligned wrong and the round bends and jams the action about 1/2" from closing. At that point, the round is not locked to the bolt face and I can draw it back using the charging handle without the round attached. To get the bent and jammed round out of the bore, I can either push it from the muzzle end with a cleaning rod or let the bolt fall hard and then force the round out using the charging handle.

The bent round is at https://i.imgur.com/3Hy8yHm.jpg

I took a close look at all 31 bent and damaged rounds, some are displayed at


Everyone has the bend and scratch marks located at exactly the same orientation on the unfired round. My son thinks something is wrong with the barrel. I'm thinking extreme over gassed, even on suppressed setting. When set on normal or adverse, the failure rate is higher. The only ammo that has low or no fails is Hornady 75gr TAP SBR 5.56 or Hornady 40gr V-Max .223. Both chrono at very consistent velocities and eject at 3:30-4:00. All of the fails seem to eject near 1:00 or all over the clock face and load from the ejection port side of the magazines.

[masterdrago]

SMH... Do you really want the guy walking out onto a public range with an unregistered SBR, with no idea what he's inadvertently done?? I certainly don't! If the OP chooses to do so, let him do it as discreetly as possible, and without having discussed it on a public forum.

I'm going to get one of my sons' shorty builds (lower stamped SBR - and I'm on his trust) to run that experiment using my Sig 10" upper next week.

[masterdrago]

I decided to polish the sharp point that seems to always get brass on it. This is on the ejection port side (right) where the new round seems to get cut as it feeds from the magazine. Top is b4. Bottom is after polishing with Fritz. Should fire some rounds mid week. I should get the Sony RX100 rental and a new gas valve from CDNN. Hoping it will have smaller ports, but since nobody seems to know (not even the Sig CS guy), I'll measure when it gets here. Second image is the original.