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A Tale of Two Crush Washers, or Two Crush Washers One Barrel, and other AR oddities

This past week or two has been an interesting one in fixing AR’s with issues, or that were improperly assembled from the get-go.

I have fixed a lot of improperly assembled AR‘s that were created by the owner, as well as AR’s that were built by several well-known local shops.

No detents or detent springs in the takedown/pivot pins, a takedown spring used instead of a selector spring, misaligned gas blocks (that’s a common theme nowadays), improperly installed muzzle devices (crush washers backwards, suppressor-attachment devices not properly secured, etc), wrong length of gas tube used (“But, a 16” barrel is a CARBINE, so why wouldn’t I use a carbine gas tube?!”), no gas tube pin installed, and more.

The word “milspec” is used by nearly every unscrupulous AR parts manufacturer and dealer on the market. Just because an ad says “milspec”, it doesn’t mean that it is. For instance, the specs for a milspec BCG are:

-Carpenter 158 steel in the bolt
-8620 steel in the carrier
-Grade 8 bolts, double staked, in the gas key
-Gas key and carrier bore chrome-plated
-Manganese phosphate finish
-100% test-fired
-High Pressure Test
-Magnetic Particle Inspected

There are also reams of specs for measurements, tolerances, etc.

So, the ad for a nitride-coated, 9310 steel bolt, “milspec” BCG is a lie.

Dwell time is a thing, and a very important thing. One of the keys to dwell time is the distance between the gas port and the muzzle in the barrel. Dwell time doesn’t start until the bullet passes the port, and it immediately stops when the bullet exits the muzzle. The positive work done by the gas system has to occur in that short length of time. The shorter that distance, the larger the port to compensate. Carbine-length gas systems are not a good idea in a 12.5” barrel, and are downright asinine in an 11.5” (I’m looking at you, Faxon).

In a 5.56, I prefer midlength gas systems in barrels 13.7” and longer, and carbine-length in barrels 10.3” - 12.5”. I don’t recommend barrels shorter than 10.3”.

The TDP is readily available on the internet. I’ve posted a link to it here on ODT before. Don’t believe me when I say the castle nut should be torqued 38-42ft/lbs and staked twice? Check the TDP.

Not all parts will be in the TDP, because not all parts are US government-issued. In those instances, use the practices and techniques recommended by the manufacturer.

If the bolts on your $49.95 15” MLOK rail are metric, that’s your second clue that it’s a made-in-China-piece-of-****. The first clue was that you paid $49.95 for it.

I nearly always have the time at TruPrep to chat with customers, answer questions, and educate them on the AR. It’s one of the main reasons I was hired. Folks apologize for “taking up my time”, and I assure them that it is part of my job.

I teach an AR Builder’s / Armorer’s Course roughly every other month. The next one is September 10 at TruPrep in Marietta. I am try to be very clear in my courses what are facts backed up by TDP, manufacturer’s specs, tests conducted by such entities as Crane NSWF, etc., and what are personal/professional opinion that I came up with on my own over more than 30 years of using, fixing, upgrading, and building M16’s/M4’s/SMG’s/AR’s.

I continue to educate and train myself as much as I can. I correspond with recognized experts in the field, and attend formal training whenever possible. I last attended an AR Armorer’s courses in the last few months. I learned a few things there that I hadn’t quite put together before.

There are other courses held around the US. I can recommend the traveling course taught by Mike Mihalski of SOLGW, and School of the American Rifle held in MD.

Get out there, get informed, and get trained.
 
Barrels and bolts are THE places people should be putting money into with their “builds”. I always like to see builds with nice muzzle devices, furniture, cerakote, etc but the functional components are garbage and the gun ends up being a paper weight. 🙄
most gun owners are hobbysts they just dont care
 
This past week or two has been an interesting one in fixing AR’s with issues, or that were improperly assembled from the get-go.

I have fixed a lot of improperly assembled AR‘s that were created by the owner, as well as AR’s that were built by several well-known local shops.

No detents or detent springs in the takedown/pivot pins, a takedown spring used instead of a selector spring, misaligned gas blocks (that’s a common theme nowadays), improperly installed muzzle devices (crush washers backwards, suppressor-attachment devices not properly secured, etc), wrong length of gas tube used (“But, a 16” barrel is a CARBINE, so why wouldn’t I use a carbine gas tube?!”), no gas tube pin installed, and more.

The word “milspec” is used by nearly every unscrupulous AR parts manufacturer and dealer on the market. Just because an ad says “milspec”, it doesn’t mean that it is. For instance, the specs for a milspec BCG are:

-Carpenter 158 steel in the bolt
-8620 steel in the carrier
-Grade 8 bolts, double staked, in the gas key
-Gas key and carrier bore chrome-plated
-Manganese phosphate finish
-100% test-fired
-High Pressure Test
-Magnetic Particle Inspected

There are also reams of specs for measurements, tolerances, etc.

So, the ad for a nitride-coated, 9310 steel bolt, “milspec” BCG is a lie.

Dwell time is a thing, and a very important thing. One of the keys to dwell time is the distance between the gas port and the muzzle in the barrel. Dwell time doesn’t start until the bullet passes the port, and it immediately stops when the bullet exits the muzzle. The positive work done by the gas system has to occur in that short length of time. The shorter that distance, the larger the port to compensate. Carbine-length gas systems are not a good idea in a 12.5” barrel, and are downright asinine in an 11.5” (I’m looking at you, Faxon).

In a 5.56, I prefer midlength gas systems in barrels 13.7” and longer, and carbine-length in barrels 10.3” - 12.5”. I don’t recommend barrels shorter than 10.3”.

The TDP is readily available on the internet. I’ve posted a link to it here on ODT before. Don’t believe me when I say the castle nut should be torqued 38-42ft/lbs and staked twice? Check the TDP.

Not all parts will be in the TDP, because not all parts are US government-issued. In those instances, use the practices and techniques recommended by the manufacturer.

If the bolts on your $49.95 15” MLOK rail are metric, that’s your second clue that it’s a made-in-China-piece-of-****. The first clue was that you paid $49.95 for it.

I nearly always have the time at TruPrep to chat with customers, answer questions, and educate them on the AR. It’s one of the main reasons I was hired. Folks apologize for “taking up my time”, and I assure them that it is part of my job.

I teach an AR Builder’s / Armorer’s Course roughly every other month. The next one is September 10 at TruPrep in Marietta. I am try to be very clear in my courses what are facts backed up by TDP, manufacturer’s specs, tests conducted by such entities as Crane NSWF, etc., and what are personal/professional opinion that I came up with on my own over more than 30 years of using, fixing, upgrading, and building M16’s/M4’s/SMG’s/AR’s.

I continue to educate and train myself as much as I can. I correspond with recognized experts in the field, and attend formal training whenever possible. I last attended an AR Armorer’s courses in the last few months. I learned a few things there that I hadn’t quite put together before.

There are other courses held around the US. I can recommend the traveling course taught by Mike Mihalski of SOLGW, and School of the American Rifle held in MD.

Get out there, get informed, and get trained.

How did the builder not immediately see that "wrong length of gas tube used" wasn't going to work?
 
How did the builder not immediately see that "wrong length of gas tube used" wasn't going to work?

No idea.

On one, the builder put a carbine length gas tube in a midlength gun. Wouldn’t cycle.

On another, the builder used a midlength gas tube when he should have used a carbine length. Couldn’t figure out why his BCG wouldn’t seat fully into the receiver.
 
Built guns really are buyer beware. They can be worse than used cars. I feel like part of the issue is cheap part manufacturers combined with bad information on the internet ( facebook groups) about what is and is quality and correct assembly. A no name gun can perform flawlessly 30 rounds at a time, twice a year. A name brand gun assembled incorrectly may not even hand cycle. You have to know what you are looking at and that knowledge costs money.

I worked with a guy last year that was a self proclaimed ar guru. He built a few uppers for other coworkers and one for himself in 50 beaowulf. I asked him the weekend after he finished his personal gun how it shot and he said it fired once and seized up. Sometimes that happens. I asked him what brand the barrel and bolt were......bear creek armory. Fiends don't let friends build junk.
 
Built guns really are buyer beware. They can be worse than used cars. I feel like part of the issue is cheap part manufacturers combined with bad information on the internet ( facebook groups) about what is and is quality and correct assembly. A no name gun can perform flawlessly 30 rounds at a time, twice a year. A name brand gun assembled incorrectly may not even hand cycle. You have to know what you are looking at and that knowledge costs money.

I worked with a guy last year that was a self proclaimed ar guru. He built a few uppers for other coworkers and one for himself in 50 beaowulf. I asked him the weekend after he finished his personal gun how it shot and he said it fired once and seized up. Sometimes that happens. I asked him what brand the barrel and bolt were......bear creek armory. Fiends don't let friends build junk.

There are brands I don’t recommend at all.

There are brands that I will recommend, with caveats.

There are brands that I will recommend wholeheartedly when it comes to certain parts.
 
Built guns really are buyer beware. They can be worse than used cars. I feel like part of the issue is cheap part manufacturers combined with bad information on the internet ( facebook groups) about what is and is quality and correct assembly. A no name gun can perform flawlessly 30 rounds at a time, twice a year. A name brand gun assembled incorrectly may not even hand cycle. You have to know what you are looking at and that knowledge costs money.

I worked with a guy last year that was a self proclaimed ar guru. He built a few uppers for other coworkers and one for himself in 50 beaowulf. I asked him the weekend after he finished his personal gun how it shot and he said it fired once and seized up. Sometimes that happens. I asked him what brand the barrel and bolt were......bear creek armory. Fiends don't let friends build junk.
100%. The first AR I "built"...Shep built it and I watched. Only bought quality, recommended parts. compared to the rest of the built...the BCM receiver set was the cheap out.

This past week or two has been an interesting one in fixing AR’s with issues, or that were improperly assembled from the get-go.

I have fixed a lot of improperly assembled AR‘s that were created by the owner, as well as AR’s that were built by several well-known local shops.

No detents or detent springs in the takedown/pivot pins, a takedown spring used instead of a selector spring, misaligned gas blocks (that’s a common theme nowadays), improperly installed muzzle devices (crush washers backwards, suppressor-attachment devices not properly secured, etc), wrong length of gas tube used (“But, a 16” barrel is a CARBINE, so why wouldn’t I use a carbine gas tube?!”), no gas tube pin installed, and more.

The word “milspec” is used by nearly every unscrupulous AR parts manufacturer and dealer on the market. Just because an ad says “milspec”, it doesn’t mean that it is. For instance, the specs for a milspec BCG are:

-Carpenter 158 steel in the bolt
-8620 steel in the carrier
-Grade 8 bolts, double staked, in the gas key
-Gas key and carrier bore chrome-plated
-Manganese phosphate finish
-100% test-fired
-High Pressure Test
-Magnetic Particle Inspected

There are also reams of specs for measurements, tolerances, etc.

So, the ad for a nitride-coated, 9310 steel bolt, “milspec” BCG is a lie.

Dwell time is a thing, and a very important thing. One of the keys to dwell time is the distance between the gas port and the muzzle in the barrel. Dwell time doesn’t start until the bullet passes the port, and it immediately stops when the bullet exits the muzzle. The positive work done by the gas system has to occur in that short length of time. The shorter that distance, the larger the port to compensate. Carbine-length gas systems are not a good idea in a 12.5” barrel, and are downright asinine in an 11.5” (I’m looking at you, Faxon).

In a 5.56, I prefer midlength gas systems in barrels 13.7” and longer, and carbine-length in barrels 10.3” - 12.5”. I don’t recommend barrels shorter than 10.3”.

The TDP is readily available on the internet. I’ve posted a link to it here on ODT before. Don’t believe me when I say the castle nut should be torqued 38-42ft/lbs and staked twice? Check the TDP.

Not all parts will be in the TDP, because not all parts are US government-issued. In those instances, use the practices and techniques recommended by the manufacturer.

If the bolts on your $49.95 15” MLOK rail are metric, that’s your second clue that it’s a made-in-China-piece-of-****. The first clue was that you paid $49.95 for it.

I nearly always have the time at TruPrep to chat with customers, answer questions, and educate them on the AR. It’s one of the main reasons I was hired. Folks apologize for “taking up my time”, and I assure them that it is part of my job.

I teach an AR Builder’s / Armorer’s Course roughly every other month. The next one is September 10 at TruPrep in Marietta. I am try to be very clear in my courses what are facts backed up by TDP, manufacturer’s specs, tests conducted by such entities as Crane NSWF, etc., and what are personal/professional opinion that I came up with on my own over more than 30 years of using, fixing, upgrading, and building M16’s/M4’s/SMG’s/AR’s.

I continue to educate and train myself as much as I can. I correspond with recognized experts in the field, and attend formal training whenever possible. I last attended an AR Armorer’s courses in the last few months. I learned a few things there that I hadn’t quite put together before.

There are other courses held around the US. I can recommend the traveling course taught by Mike Mihalski of SOLGW, and School of the American Rifle held in MD.

Get out there, get informed, and get trained.
Learned from you that an aluminum end plate(radian, from Truprep lol) can't really be staked and to use vibra-tite VC3 for those applications. People should always reach out and just ask questions.
 
100%. The first AR I "built"...Shep built it and I watched. Only bought quality, recommended parts. compared to the rest of the built...the BCM receiver set was the cheap out.


Learned from you that an aluminum end plate(radian, from Truprep lol) can't really be staked and to use vibra-tite VC3 for those applications. People should always reach out and just ask questions.
Shep has fixed several of mine, including one carrier key that I broke a cotton swab off in, then a tap trying to get the swab out. I watched him replace the key. He is my go to guy on ARs.
 
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