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Posted: 7/20/2015 2:24:59 PM EDT
| I have a PSA upper and lower rifle, with a AIM BCG. Took it to the range for the first time today. It feeds fine, but when it ejects the brass just plops down right next to the rifle, instead of flying 2-3 feet away. I'm new to AR's so any help is appreciated. |
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Quoted:
The cases look fine. The BCG is brand new from AIM Surplus, so the spring should be good. Not knocking AIM Surplus, I have bought a few of their BCG's but it happens regardless of the make. To check it, if you are running a standard extractor spring add a #60 O-ring around the extractor spring to add some more testing tension to the extractor to confirm that the spent is not being dropped prematurely, and the problem at hand instead. |
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if you are running a standard extractor spring add a #60 O-ring around the extractor spring to add some more testing tension to the extractor to confirm that the spent is not being dropped prematurely, and the problem at hand instead. I don't think much troubleshooting can be done until all the facts are here. Ammo type, barrel length, gas tube setup (if applies), buffer, buffer spring and so on. Assuming all the simple stuff is normal, you would have short stroking of the action. That might be caused by an incorrect buffer or spring, or incorrect timing - not enough gas pressure or not at the right time. It should be obvious if you have a defective BCG. Key is staked and tight, the bolt/cam assembly works, and the gas rings are working and in place, ejector moves freely with normal spring pressure, extractor checks ok and moves freely. I assume you have done these simple checks. Let's take a moment to clarify the o-ring defender myth. Do we know what all the fuss is about? Think about the idea of adding additional extractor tension on a case, (as if there weren't enough there already). You are then saying that the extractor hook is incorrectly designed or the angles of the extractor claw are incorrect, or the designers just did not know enough about the extractor and spring so they just flipped a coin. That's a big leap to make, isn't it? Let's add this fact: the extractor rotational masses are designed to grasp the case rim during rearward movement of the bolt carrier. In other words, even without a spring the extractor rotates toward the case rim as it is moving rearwards. This would suggest that you would get extraction and ejection even without an extractor spring. Well, we can have a class on that subject another time. Proper operation of the extraction cycle: chamber pressure subsides sufficiently for the case to contract - all before the BCG tries to pull the case out of the chamber. If the BCG/extractor tries to pull an expanded case out of a pressurized barrel, then naturally you are either going to break your extractor, have the extractor rip the rim off the case or have the extractor claw give up and let go of the case rim. The problem in such a case is not a weak extractor spring. It is timing which means location and size of the gas port, and length of the gas tube for a particular barrel, as well as the action spring and buffer. Semi-auto operation should never require fooling with the extractor spring. The o-rings and magic defender pads were created as a band-aid fix for problems that come up during automatic firing of customized weapons. The original platform did not require added gizmos to work reliably during auto fire. With shorter barrel lengths and cycling rates come new parameters requiring redesign of the gas port location, gas tube length, buffer, buffer spring, extractor, ejector and so on. In auto fire, you have the added headache of damping spring resonances - which can occur in any of the springs, and can interfere with smooth automatic fire cycling. There is no need for extractor spring adjustment on a semi-auto action. In correct operation the extractor does not have to rip the case out of the chamber prematurely. Remember that increasing the extractor spring tension works 2 ways. During chambering the extractor has to snap over the case rim from behind - which is made more difficult with a stronger spring (think extractor claw damage, premature wear, difficulty going into battery, etc. If the magic o-ring improves operation you have a more basic timing problem or faulty BCG which should be fixed. It's a band-aid. Wouldn't you rather have the real fix? Basics first. WhiteFox |
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