Question about a customer's gun: 10.5" SBR w/ suppressor

[Leonidas24]

Had a guy bring in a suppressed PWS 10.5" SBR today to test out with an AAC Ranger 2. The gun cycled fine without the suppressor using Federal XM193BK albeit with a nice fireball.

When he added the suppressor to the gun it appeared that the bolt began to outrun the magazine and the next round would start to load but would end up smashed against the feed ramps. In addition some of the ejected cases were just barely falling out of the ejection port and even causing a stove pipe once ever 6-7 rounds.

I broke down the gun and checked everything over. Everything was stock PWS except the buffer which was a Spikes T2. Apparently there was a carbine buffer in the gun but he switched it out when he got it. In addition the entire gun was bone dry. I lubed the gun after checking everything over but noticed that the extractor spring looked a little small, and the insert almost looked crushed in a way. The ejector felt like it had enough tension behind it but other than that everything looked normal.

I said he might try switching to an H3 buffer or heavier spring to slow down the bolt, and replace the extractor spring and insert with one from BCM to see if that solves the problem. Other than some inherent issue with the gun, are there any other parts that could be replaced that might alleviate the issue?

[Iraqgunz]

I would go with an H3 buffer and blue Springco spring.

The alternate would be to get the A5. It is the overall smartest choice.


Had a guy bring in a suppressed PWS 10.5" SBR today to test out with an AAC Ranger 2. The gun cycled fine without the suppressor using Federal XM193BK albeit with a nice fireball.

When he added the suppressor to the gun it appeared that the bolt began to outrun the magazine and the next round would start to load but would end up smashed against the feed ramps. In addition some of the ejected cases were just barely falling out of the ejection port and even causing a stove pipe once ever 6-7 rounds.

I broke down the gun and checked everything over. Everything was stock PWS except the buffer which was a Spikes T2. Apparently there was a carbine buffer in the gun but he switched it out when he got it. In addition the entire gun was bone dry. I lubed the gun after checking everything over but noticed that the extractor spring looked a little small, and the insert almost looked crushed in a way. The ejector felt like it had enough tension behind it but other than that everything looked normal.

I said he might try switching to an H3 buffer or heavier spring to slow down the bolt, and replace the extractor spring and insert with one from BCM to see if that solves the problem. Other than some inherent issue with the gun, are there any other parts that could be replaced that might alleviate the issue?

[GrumpyM4]

I think you started in the right place.

What his gun is expereincing is a clear sign of being way overgassed or has other issues that mimic overgassing. Or it could be a combination of the two. Ensuring the ejector spring is within spec would be my first check, followed by a heavier spring (as IG said) or even changing out the entire stock to an A5, also like IG said.

If the gun runs a very strong ejection even without the can and the ejector spring is within spec, perhaps even a Wolff XP spring might be in order, even on top of an A5 stock swap.

I don't normally like going outside of milspec parts to fix issues, but shorties sometimes require special attention.

[Leonidas24]

I would go with an H3 buffer and blue Springco spring.

The alternate would be to get the A5. It is the overall smartest choice.

I figured as much. From what I gathered it was his first AR and the inexperience coupled with a troubled SBR and suppressor compounded the issue. I'm assuming that replacing the extractor spring with a 5-coil from BCM would just be good practice at this point.

Grumpy: From what I could tell the ejector was under a decent amount of pressure. I couldn't force a round under the extractor claw with ease. Unless you're talking about the buffer spring, which would make a lot more sense. :D

[GrumpyM4]

Grumpy: From what I could tell the ejector was under a decent amount of pressure. I couldn't force a round under the extractor claw with ease. Unless you're talking about the buffer spring, which would make a lot more sense. :D

No, I was talking about the ejector spring.

One of the things that can mimic an overgassed gun or can contribute to these kinds of malfunctions is a weak ejector spring.

If the spring isn't strong enough, it won't be pushing the brass out of the ejection port quick enough, especially if the bolt is too fast.

Under "normal" conditions, this simply results in a forward brass throw pattern. No big deal. Simply replace the ejector spring and the brass will be exiting the ejection port in a timely manner and impacting the brass deflector properly and acting just fine.

On the other hand, if your bolt speed is increased by running a shorter gun with a larger gas port (increased bolt speed), it can result in extreme forward brass throw, up to and including having the brass damage your handguards (i've seen it), and then if it's overgassed excessivly or a can is added, it can literally bounce expended brass right back into the ejection port and result in these stovepipe type malfunctions.

If there is something catching on the ejector, slowing it down, or the spring is weak, under the right conditions, the bolt can travel rearward fast enough so that by the time the brass is starting to leave the ejection port, it is impacting on the inside rear edge of the ejection port and getting sent right back into the receiver. SOmetimes it'll get bounced out, and other times it'll get caught by the bolt and malfunction like a stovepipe.

Check the wear patterns on the rear of the ejection port and see where the anodizing is being impacted by the spent brass.

While a weak ejector spring is, for the most part, a minor annoyance in brass throw (which I think is why many here poo-poo the ejection chart), it can contribute to the more extreme issues such as the one your client is dealing with.

I recently delt with a gun that acted extremely overgassed and also had some other issues. Saber defense barrel, around 1k rounds down the pipe.

After dealing with the extraction issue, I simply couldn't figure out the stovepiping issue, almost exactly like what you describe. I checked gas port size and erosion, was ok. Shot the gun with several BCGs and noted that the oldest BCG I had caused signifcantly more stovepipes.

In the end, the best I can figure is that the throat is undersized and is causeing severe pressure issues, so the barrel was replaced.

Point being is that while the main issue lies elsewhere, the ejector spring can make things worse if it is weak.

[sinlessorrow]

There was a thread over on TOS about PWS being overgassed suppressed.

If you look at their cut away you will see why they act like they do suppressed