User Panel
[#1]
Outstanding work Steve.
Very few people get to see cutaway drawing and I think you will clear up a lot of peoples misconceptions. |
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Good, Bad... I'm the guy with the Gun
Without the neccessary toughness to apply training in adverse situations, the training is valueless |
[#2]
thanks for taking the time to write this in here.I like the ones you have done, like the stainless barrel wear and trigger.
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[#3]
good write up
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[#4]
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[#5]
So, that brings up a question regarding the AR piston conversions.
Most of these conversions appear to apply pressure to the bolt carrier at the location where they gas tube usually enters. Therefore the pressure to move the carrier back is no longer coming from "in line" internal gas expansion, but from "off center" direct pressure. This "off center" pressure must put stress on the AR BCG and upper that it wasn't originally designed to handle, no? |
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"The enemy," retorted Yossarian with weighted precision, "is anybody who's going to get you killed, no matter which side he's on." - Catch 22
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[#6]
Originally Posted By Monoz:
This "off center" pressure must put stress on the AR BCG and upper that it wasn't originally designed to handle, no? you are correct |
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I'm no good at telling people what they want to hear when I dont believe it myself :)
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[#7]
Originally Posted By bigbore:
Originally Posted By Monoz:
This "off center" pressure must put stress on the AR BCG and upper that it wasn't originally designed to handle, no? you are correct That's the whole "carrier tilt" issue with piston ARs. The AR15 upper receiver and bolt carrier aren't designed for and don't have a provision to properly control that motion. |
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This is...a clue. - Pat_Rogers
Here's where the fundamentals are coming in... - costa |
[#8]
Originally Posted By Gamma762:
That's the whole "carrier tilt" issue with piston ARs. The AR15 upper receiver and bolt carrier aren't designed for and don't have a provision to properly control that motion. I was completely ignorant of this - googling "carrier tilt" has started to clue me in. |
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"The enemy," retorted Yossarian with weighted precision, "is anybody who's going to get you killed, no matter which side he's on." - Catch 22
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[#9]
Fantastic write up, and it really shows the genius of the design.
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كافر
"Take care of your asshole, gentlemen, and it will take care of you. Its the only one you'll ever have." - axl |
[#10]
im all about this write up.
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Nasty Midnighter(this thread is racist.)
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[#11]
The aspect of the piston in an AR making the BCG tilt makes sense. Ive seen some photos of this wear on the front part of the buffer tube. Thats enough for me.
Im glad I found this thread as I was about to drop some bucks on a new piston carbine. Now I think I will just put the funds toward more ammo, which is what I really wanted to do anyway. |
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[#13]
tagggg
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No police, no summons, no courts of law, No proper procedure, no rules of war
No mitigating circumstance, No lawyers fees, no second chance |
[#14]
There is another benefit to the original DI system, that being the bolt is unloaded by the rearward motion of the carrier+buffer when the gas enters the cylinder. Newton's Third Law, every action has an equal and opposite reaction. This isn't trivial, it is 3000-8000 pounds of force which happens shortly after the bullet passes the port. Because of this forward force on the bolt, the locking lugs are unloaded, reducing wear and tear on these surfaces. Wear on these surfaces is the primary mode of headspace growth.
The brass cartridge case expands as a result of the pressure rise but because of spring back, it doesn't fully expand to fill the chamber. But spring back is less than thermal expansion which WILL cause the case to fully load the bolt's lugs until the case cools. This isn't a problem with bolt action rifles but is is with semi-autos. Cycle any bolt gun as fast as you can after firing, catching the brass. It will be barely warm. Not so in a semi-auto, brass from a 5.56 can cause skin burns. |
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AR15.COM's Polymath
Ars sine scientia nihil est |
[#15]
Thank you for this. Very helpful and informative.
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Pour me another drink and pass the ammunition.
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girl...girl...girl...I know you hear me
FL, USA
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[#16]
Originally Posted By SOC: Originally Posted By Gamma762: Originally Posted By bigbore: Originally Posted By Monoz: This "off center" pressure must put stress on the AR BCG and upper that it wasn't originally designed to handle, no? you are correct That's the whole "carrier tilt" issue with piston ARs. The AR15 upper receiver and bolt carrier aren't designed for and don't have a provision to properly control that motion. Carrier Tilt = Chewed up buffer tube (You can use a new anti tilt buffer and/or extend the buffer tube into the upper enough that the carrier rests on it in the locked position) Cam pin drag = Gouge in upper from cam pin digging into it (You can add a spring on the bolt tail that pushes at the carrier from inside and/or use a Roller bearing cam pin from POF) As far as a piston upper being better with suppressor use, that's total bunk. The Piston guns get as dirty as the DI guns. http://www.thefirearmblog.com/blog/wp-content/uploads/2009/06/3548680695-2d8feb0d23-b-tm1.jpg http://www.thefirearmblog.com/blog/wp-content/uploads/2009/06/3548689487-8449978d0e-b-tm.jpg http://www.thefirearmblog.com/blog/wp-content/uploads/2009/06/3548691655-4ae7aa2caf-b-tm1.jpg http://www.thefirearmblog.com/blog/wp-content/uploads/2009/06/3548693999-efaf0fe1d3-b-tm.jpg As for gas in your eye just use a little gasket sealant on your charging handle. That's from the 416 upper and the guy shot an enormous amount of ammo through it. I'm not a DI hater but a DI AR would look like a charcoal briquette after the same treatment. |
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[#17]
Anyone have a link to that thread?
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Recent college graduate w/ a B.S. looking for a job in the LE/Private security field.
"Marines guard the streets of Heaven. Who else would God trust?" Kevin Waruinge, KIA 8-3-05 |
[Last Edit: Gamma762]
[#18]
Originally Posted By Keith_J:
Because of this forward force on the bolt, the locking lugs are unloaded, reducing wear and tear on these surfaces. Wear on these surfaces is the primary mode of headspace growth. I've also had the thought for a while now that this mechanism not being correctly in time is why carbine gas 14.5 & 16" barrel ARs have a tendency to shear the locking lugs next to the extractor. Those lugs have nearly no lateral support, and in those gas system configurations the bolt is still under rearward force when unlocking starts, putting lateral stress on the lugs. I've come to believe that forward push as a correctly applied balancing force during unlocking is an important part of the operating cycle and one of the most genius aspects of the design. |
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This is...a clue. - Pat_Rogers
CO, FL, MI, SC, NH, NV - Please lobby your legislators to end discrimination against non-resident CCW permit holders |
[#19]
Has anyone removed a barrel extension on a piston gun to see the inside locking lug wear and bolt lug wear pattern compared to DI?
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No matter what you say about The South, I've never heard of anyone wanting to retire to The North
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[#20]
And in spite of all that, mine wouldn't function reliably with Wolf ammo.
Long live the AK! |
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[Last Edit: TexasRifleman1985]
[#21]
Originally Posted By amd_dude: Originally Posted By SOC: Originally Posted By Gamma762: Originally Posted By bigbore: Originally Posted By Monoz: This "off center" pressure must put stress on the AR BCG and upper that it wasn't originally designed to handle, no? you are correct That's the whole "carrier tilt" issue with piston ARs. The AR15 upper receiver and bolt carrier aren't designed for and don't have a provision to properly control that motion. Carrier Tilt = Chewed up buffer tube (You can use a new anti tilt buffer and/or extend the buffer tube into the upper enough that the carrier rests on it in the locked position) Cam pin drag = Gouge in upper from cam pin digging into it (You can add a spring on the bolt tail that pushes at the carrier from inside and/or use a Roller bearing cam pin from POF) As far as a piston upper being better with suppressor use, that's total bunk. The Piston guns get as dirty as the DI guns. http://www.thefirearmblog.com/blog/wp-content/uploads/2009/06/3548680695-2d8feb0d23-b-tm1.jpg http://www.thefirearmblog.com/blog/wp-content/uploads/2009/06/3548689487-8449978d0e-b-tm.jpg http://www.thefirearmblog.com/blog/wp-content/uploads/2009/06/3548691655-4ae7aa2caf-b-tm1.jpg http://www.thefirearmblog.com/blog/wp-content/uploads/2009/06/3548693999-efaf0fe1d3-b-tm.jpg As for gas in your eye just use a little gasket sealant on your charging handle. That's from the 416 upper and the guy shot an enormous amount of ammo through it. I'm not a DI hater but a DI AR would look like a charcoal briquette after the same treatment. I've run my ARs until they look like charcoal briquettes on the inside... And they still run. Keep them very wet and the carbon fouling will clean itself off of the important contact surfaces, allowing it to continue functioning... Virtually indefinitely. Two years of heavy training (over 30K rounds per year) on one of my older rifles without a single non-magazine caused malfunction, never cleaned it in the slightest, just kept it dripping wet. I have more than enough confidence in the system. I am, however, a fan of OCD cleaning of all my go-to weapons, not because they require it for function, but because it allows you to intimately inspect the weapon for parts wear or failures. Pay particular attention to the bolt on the AR, it does tend to wear out somewhat quickly. The under-engineered cam pin hole and cam pin is my only complaint on the system. A good DI gun still runs longer without a mechanical failure than any piston-fucked AR in my experience. Pistol guns break, from what I've seen. TR85. |
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Hear the call of the fallen ones
Wisdom of those whose time has gone Live your life bravely my first born son, On battlefields, fight, don't run. |
[#22]
I went with a piston after having problems with my 6.8 DI. After two gas block changes and all the associated fooling around with pins, alignment, leak checks and absolutely mysterious problems, I'm hoping to see an improvement. Won't know until I go to the range, but if it goes bang when I pull the trigger and feeds the next round, I'll be happy.
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"So? We are democrats! If we tell the truth we will never win an election, period!!"
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[#23]
So how does this affect other calibers since the DI system was designed around the 5.56mm? Say 6.8mm or the big guy I'm interested in the 8.6mm (.338 LM)? The latter I've only seen in piston form. I'm a DI guy but I don't know if the larger cartridge and pressures will necessitate a piston or not.
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[#24]
Originally Posted By TexasRifleman1985:
Originally Posted By amd_dude:
Originally Posted By SOC:
Originally Posted By Gamma762:
Originally Posted By bigbore:
Originally Posted By Monoz:
This "off center" pressure must put stress on the AR BCG and upper that it wasn't originally designed to handle, no? you are correct That's the whole "carrier tilt" issue with piston ARs. The AR15 upper receiver and bolt carrier aren't designed for and don't have a provision to properly control that motion. Carrier Tilt = Chewed up buffer tube (You can use a new anti tilt buffer and/or extend the buffer tube into the upper enough that the carrier rests on it in the locked position) Cam pin drag = Gouge in upper from cam pin digging into it (You can add a spring on the bolt tail that pushes at the carrier from inside and/or use a Roller bearing cam pin from POF) As far as a piston upper being better with suppressor use, that's total bunk. The Piston guns get as dirty as the DI guns. http://www.thefirearmblog.com/blog/wp-content/uploads/2009/06/3548680695-2d8feb0d23-b-tm1.jpg http://www.thefirearmblog.com/blog/wp-content/uploads/2009/06/3548689487-8449978d0e-b-tm.jpg http://www.thefirearmblog.com/blog/wp-content/uploads/2009/06/3548691655-4ae7aa2caf-b-tm1.jpg http://www.thefirearmblog.com/blog/wp-content/uploads/2009/06/3548693999-efaf0fe1d3-b-tm.jpg As for gas in your eye just use a little gasket sealant on your charging handle. That's from the 416 upper and the guy shot an enormous amount of ammo through it. I'm not a DI hater but a DI AR would look like a charcoal briquette after the same treatment. I've run my ARs until they look like charcoal briquettes on the inside... And they still run. Keep them very wet and the carbon fouling will clean itself off of the important contact surfaces, allowing it to continue functioning... Virtually indefinitely. Two years of heavy training (over 30K rounds per year) on one of my older rifles without a single non-magazine caused malfunction, never cleaned it in the slightest, just kept it dripping wet. I have more than enough confidence in the system. I am, however, a fan of OCD cleaning of all my go-to weapons, not because they require it for function, but because it allows you to intimately inspect the weapon for parts wear or failures. Pay particular attention to the bolt on the AR, it does tend to wear out somewhat quickly. The under-engineered cam pin hole and cam pin is my only complaint on the system. A good DI gun still runs longer without a mechanical failure than any piston-fucked AR in my experience. Pistol guns break, from what I've seen. TR85. Piston guns are more tollerant of debris and lack of cleaning. This was clearly proven in the Dust test. The DI guns failed badly when exposed to sand and dust while the piston guns ran longer. That isn't to say DI guns suck...but pistons have their place. |
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[#25]
Thanks for the informative writeup. Very well written.
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We the People .... do ordain and establish this Constitution for the United States of America.
"The beauty of the Second Amendment is that you won't need it until they try to take it away." Thomas Jefferson Never Forget 9/11 Still pissed! |
[#26]
Fantastic explanation, just saw it another thread here. Great stuff. Thanks.
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Verbum Domini Manet in Aeternum
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[Last Edit: curmudgeon10]
[#27]
bigbore: Thanks a lot for showing/telling how my AR-15 works internally; clears up many questions that were rattling around in my brain. Fantastic !!!
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[Last Edit: sinlessorrow]
[#28]
Originally Posted By LockingBlock:
Originally Posted By TexasRifleman1985:
Originally Posted By amd_dude:
Originally Posted By SOC:
Originally Posted By Gamma762:
Originally Posted By bigbore:
Originally Posted By Monoz:
This "off center" pressure must put stress on the AR BCG and upper that it wasn't originally designed to handle, no? you are correct That's the whole "carrier tilt" issue with piston ARs. The AR15 upper receiver and bolt carrier aren't designed for and don't have a provision to properly control that motion. Carrier Tilt = Chewed up buffer tube (You can use a new anti tilt buffer and/or extend the buffer tube into the upper enough that the carrier rests on it in the locked position) Cam pin drag = Gouge in upper from cam pin digging into it (You can add a spring on the bolt tail that pushes at the carrier from inside and/or use a Roller bearing cam pin from POF) As far as a piston upper being better with suppressor use, that's total bunk. The Piston guns get as dirty as the DI guns. http://www.thefirearmblog.com/blog/wp-content/uploads/2009/06/3548680695-2d8feb0d23-b-tm1.jpg http://www.thefirearmblog.com/blog/wp-content/uploads/2009/06/3548689487-8449978d0e-b-tm.jpg http://www.thefirearmblog.com/blog/wp-content/uploads/2009/06/3548691655-4ae7aa2caf-b-tm1.jpg http://www.thefirearmblog.com/blog/wp-content/uploads/2009/06/3548693999-efaf0fe1d3-b-tm.jpg As for gas in your eye just use a little gasket sealant on your charging handle. That's from the 416 upper and the guy shot an enormous amount of ammo through it. I'm not a DI hater but a DI AR would look like a charcoal briquette after the same treatment. I've run my ARs until they look like charcoal briquettes on the inside... And they still run. Keep them very wet and the carbon fouling will clean itself off of the important contact surfaces, allowing it to continue functioning... Virtually indefinitely. Two years of heavy training (over 30K rounds per year) on one of my older rifles without a single non-magazine caused malfunction, never cleaned it in the slightest, just kept it dripping wet. I have more than enough confidence in the system. I am, however, a fan of OCD cleaning of all my go-to weapons, not because they require it for function, but because it allows you to intimately inspect the weapon for parts wear or failures. Pay particular attention to the bolt on the AR, it does tend to wear out somewhat quickly. The under-engineered cam pin hole and cam pin is my only complaint on the system. A good DI gun still runs longer without a mechanical failure than any piston-fucked AR in my experience. Pistol guns break, from what I've seen. TR85. Piston guns are more tollerant of debris and lack of cleaning. This was clearly proven in the Dust test. The DI guns failed badly when exposed to sand and dust while the piston guns ran longer. That isn't to say DI guns suck...but pistons have their place. those tests were set up poorly, if you look the summer testing showed the DI rifle only having 148 class 1&2 stoppages seen here now the issue with the fall testing done, is that the trigger pullers didnt realize how burst mode worked, so every time they only got 1 or 2 shots they counted that as a stoppage, even though it wasnt, and its how the trigger group is setup. after the fall dust test colt hired an outside DOD-certified testing agency, Stork East-West Technology Corporation in Jupiter, Florida to do the exact same dust test and came out with 111 class 1&2 stoppages. so the fall dust test was a horribly setup testing, and most of those stoppages are from not firing a 3-rnd burst fully. |
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[#29]
I love the guys at ADCO.
This is a very good read. |
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