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A Tale of Two Crush Washers, or Two Crush Washers One Barrel, and other AR oddities
- Thread starter cmshoot
- Start date
This kinda goes back to the YouTube video I posted about the Vltor A5 system. The rifle length spring and buffer system is a much more forgiving system than the carbine system. It's not working as abruptly. With the rifle system, the magazine spring has all the time it needs to fully push up and present the next round for feeding, so they won't attempt to feed "low".
The Vltor A5 brings that lack of abruptness back to the carbine buffer system, while adding some other innovations and benefits.
I’m not an expert, but I heard it also exists because of the adoption of green tip ammo. Green tips have a harder/sharper nose and the M4 extensions allow it to feed better. Can anyone confirm or debunk this?
I believe that the issue isn't the shape of the tip so much as the OAL of the two rounds. The older M193 has an OAL of 2.12", while the M855 has an OAL of 2.26". A longer OAL, combined with the possibility of rounds feeding from the mag before they're pushed up fully, would mean the tip of the round banging into the upper receiver below the feed ramps in the barrel.
Customer was at a local gun shop with an indoor range. He fired a few rounds from his home-build AR, and then it wouldn't feed. He tried to chamber a round by hand several times, and it wasn't happening. He took it to the "Armorer" that worked there. The Armorer inspected it, broke it into the upper and lower assemblies, and pulled out the buffer and buffer spring. Customer stated that he shrugged and stated, "You probably need a new buffer spring."
I took one look at the upper, and pointed out that there was an expended shell casing stuck in the chamber. It was completely intact, so how that was missed by the other Armorer is beyond me. Quick punch with a cleaning rod knocked it out.
Customer stated that he also got some light primer strikes. Armorer at the other shop stated that it was because he was using PMC ammo, which is known to blow up guns. His words, not mine. Armorer told the customer that he needs to run only Norma ammo. When I asked, the customer stated that the shop sells Norma ammo, but doesn't carry PMC. Go figger.
PMC ammo is just fine, and I told the customer that.
The extractor spring on the customer's brand new, gold TiN coated, Brownell's BCG seemed very weak. I installed a new Sprinco 5-coil extractor spring, with insert and Crane O-ring.
Soon after that I noticed that the rim on the face of the buffer was chewed up all the way around, which means that the buffer retaining pin is impacting the buffer during cycling. I checked it out, and saw that when the BCG was inserted into the upper receiver, it was either too short to make contact with the buffer, or something was allowing the BCG to sit too deep into the upper receiver. A quick look at the feed ramps showed that the face of the barrel extension was at least 1/8" from being seated all the way.
I pulled the "Geissele" rail (marked and labeled as such), pulled the gas block (which had set screws and the barrel was not dimpled), and removed the barrel nut, which was loose. Additionally, the barrel nut was black, not the gold-ish color that I have always seen on Geissele barrel nuts.
Under the barrel nut, I found that the barrel was not completely seated. The index pin on the barrel extension was not seated in it's corresponding slot in the upper receiver.
When asked, the customer stated that he bought the rail off eBay, that it was labeled as brand new, and that he paid $89 for it. I informed him that the rail was not in fact a Geissele, and was instead a Chinese forgery of a Geissele.
When I started to reassemble the upper, I found that the threaded portion of the barrel nut was too long. The barrel nut was making contact with section of the upper receiver just below the Picatinny rail, preventing the barrel nut from making contact with the barrel extension.
I shortened the barrel nut, and reinstalled the barrel. Dimpled the barrel for the gas block. Opened the gas port from .070" to .0725" to better perform with a wide variety of ammo.
I noticed that the crown on the barrel was cut at a slant, and the threaded portion was shorter than it should be. Someone cut down and threaded a longer barrel, and did a **** job of it. I advised the customer that since there was no way of telling who made the barrel, he would probably be better off replacing than the barrel rather than paying to have this one corrected. I also told him that until it was fixed or replaced, he would have accuracy issues, and to not run a suppressor on it.
Installed a Sprinco "white" buffer spring and H2 buffer. Gave the customer instructions on how to function test it at the range.
I took one look at the upper, and pointed out that there was an expended shell casing stuck in the chamber. It was completely intact, so how that was missed by the other Armorer is beyond me. Quick punch with a cleaning rod knocked it out.
Customer stated that he also got some light primer strikes. Armorer at the other shop stated that it was because he was using PMC ammo, which is known to blow up guns. His words, not mine. Armorer told the customer that he needs to run only Norma ammo. When I asked, the customer stated that the shop sells Norma ammo, but doesn't carry PMC. Go figger.
PMC ammo is just fine, and I told the customer that.
The extractor spring on the customer's brand new, gold TiN coated, Brownell's BCG seemed very weak. I installed a new Sprinco 5-coil extractor spring, with insert and Crane O-ring.
Soon after that I noticed that the rim on the face of the buffer was chewed up all the way around, which means that the buffer retaining pin is impacting the buffer during cycling. I checked it out, and saw that when the BCG was inserted into the upper receiver, it was either too short to make contact with the buffer, or something was allowing the BCG to sit too deep into the upper receiver. A quick look at the feed ramps showed that the face of the barrel extension was at least 1/8" from being seated all the way.
I pulled the "Geissele" rail (marked and labeled as such), pulled the gas block (which had set screws and the barrel was not dimpled), and removed the barrel nut, which was loose. Additionally, the barrel nut was black, not the gold-ish color that I have always seen on Geissele barrel nuts.
Under the barrel nut, I found that the barrel was not completely seated. The index pin on the barrel extension was not seated in it's corresponding slot in the upper receiver.
When asked, the customer stated that he bought the rail off eBay, that it was labeled as brand new, and that he paid $89 for it. I informed him that the rail was not in fact a Geissele, and was instead a Chinese forgery of a Geissele.
When I started to reassemble the upper, I found that the threaded portion of the barrel nut was too long. The barrel nut was making contact with section of the upper receiver just below the Picatinny rail, preventing the barrel nut from making contact with the barrel extension.
I shortened the barrel nut, and reinstalled the barrel. Dimpled the barrel for the gas block. Opened the gas port from .070" to .0725" to better perform with a wide variety of ammo.
I noticed that the crown on the barrel was cut at a slant, and the threaded portion was shorter than it should be. Someone cut down and threaded a longer barrel, and did a **** job of it. I advised the customer that since there was no way of telling who made the barrel, he would probably be better off replacing than the barrel rather than paying to have this one corrected. I also told him that until it was fixed or replaced, he would have accuracy issues, and to not run a suppressor on it.
Installed a Sprinco "white" buffer spring and H2 buffer. Gave the customer instructions on how to function test it at the range.
Some of your customers and range armorers make me feel like Chad at sotar. Wow
I was revisiting this thread and came across this. Like most folks, I know more now than I did 3 years ago.
Several companies, such as Wilson Combat and S&W, have a "rifle length" gas system in their AR10's that is approximately .250" longer than a standard rifle system. More than likely, the top barrel in the pic is set up for this proprietary gas system length. Customer did not know that, and installed a standard rifle length gas tube in it, which would be .250" too short.
Wilson Combat does sell their gas tubes separately. Good idea to stock up on spares, if you own a barrel like this. That part would be difficult to find in inventory in your LGS.
Proof research AR10s has barrels that the same way. I think white oak armory has just about every length imaginable on gas tubes. I don't know about the big frame guns, but the small frame noveske has a wierd one, also.
