Archived Posts » 59,789,155
POF Roller Cam Pin?
5/11/2012 11:36:16 PM
I have a POF rifle that has a standard Cam Pin. Should I upgrade it or leave it alone? Is it worth it?
5/11/2012 11:58:57 PM
Yes it is worthy. Please check this video
http://www.youtube.com/watch?v=6JmIQXkoog8
http://www.youtube.com/watch?v=6JmIQXkoog8
5/12/2012 12:14:29 AM
Will do thanks
ETA: that was very interesting thanks again....
ETA: that was very interesting thanks again....
5/12/2012 8:12:49 AM
Originally Posted By -Carnage-:
Yes it is worthy. Please check this video
http://www.youtube.com/watch?v=6JmIQXkoog8
Yes it is worthy. Please check this video
http://www.youtube.com/watch?v=6JmIQXkoog8
A cartridge has different characteristics in weight than holding the bolt back with your finger...
For a rifle design that has been around since 1958, I think a "problem" like that would have been addressed. However, some guy from Berlin, who prefers the AK system, posts that video, and it is so.
5/12/2012 8:47:00 AM
Originally Posted By Screwball:
A cartridge has different characteristics in weight than holding the bolt back with your finger...
For a rifle design that has been around since 1958, I think a "problem" like that would have been addressed. However, some guy from Berlin, who prefers the AK system, posts that video, and it is so.
Originally Posted By -Carnage-:
Yes it is worthy. Please check this video
http://www.youtube.com/watch?v=6JmIQXkoog8
Yes it is worthy. Please check this video
http://www.youtube.com/watch?v=6JmIQXkoog8
A cartridge has different characteristics in weight than holding the bolt back with your finger...
For a rifle design that has been around since 1958, I think a "problem" like that would have been addressed. However, some guy from Berlin, who prefers the AK system, posts that video, and it is so.
Ive always thought that video was odd.
I mean considerin i can slowly ride my CH and my BCG will strip a round out of the magazine. It wont chamber it but itll strip it.
Seems like someone who doesnt really understand the system.
5/12/2012 12:18:03 PM
Originally Posted By sinlessorrow:
...Seems like someone who doesnt really understand the system.
...Seems like someone who doesnt really understand the system.
Please check Axel's background before making a comment like this.
5/14/2012 11:25:39 PM
Whatever his background his tests do not duplicate the BCG cycling under higher pressures and speed than can be duplicated by pushing in the front of the bolt...hes not duplicating the actual cycling wich can only be achieved by firing and therfore the test is flawed and biased.Under his rationale filthy14 as tested by Pat Rogers and DI operation to boot should not have gone 42.000 rounds only cleaned twice but always lubed and never run dry.You dont see the roller cam pin used to contrast and compare.
5/15/2012 12:49:56 PM
Originally Posted By pun:
Whatever his background his tests do not duplicate the BCG cycling under higher pressures and speed than can be duplicated by pushing in the front of the bolt...hes not duplicating the actual cycling wich can only be achieved by firing and therfore the test is flawed and biased.
Whatever his background his tests do not duplicate the BCG cycling under higher pressures and speed than can be duplicated by pushing in the front of the bolt...hes not duplicating the actual cycling wich can only be achieved by firing and therfore the test is flawed and biased.
This.
5/15/2012 1:14:42 PM
Actually, the video misses the point of the roller cam pin and you need to know its purpose. In a DI gun, gas is directed inside the bolt carrier (it shits where it eats) and pushes on the bolt (the bolt rings trap the gas and this is in effect the piston-inside the bolt carrier!!). The gas pushes the bolt hard forward, sending the bolt carrier rearward. The other thing it does is force the cam pin all the way forward before the bolt starts its movement rearward. This fully aligns the cam pin behind the gas key for its rearward travel. In a piston gun, the op rod drives the carrier rearward. As the carrier is pushed rearward, the cam pin rides in its groove in the bolt carrier, turning the lugs to unlock the bolt. The second the bolt lugs clear the chamber lugs, the bolt begins its travel rearward. Depending on your guns design, the cam pin may or may not be fully aligned behind the gas key. When it is not fully aligned, this is the upper gouge occurs. An alternate solution to the roller cam would be to cut the grove in the bolt carrier precisely so the cam pin was fully behind the gas key when the lugs are freed but this would decrease reliability and require much tighter controls on where the chamber lugs wind up.
If you have been running the gun without a roller cam pin, your upper is probably already gouged. Once it reaches a certain wear point, it won't gouge it any more. However, the video brings up another point that the carrier key does use the inside track of the upper to keep the bolt unlocked while it strips the round. This really isn't a big deal if it is lubed. Look inside a DI gun that has been properly maintained and you won't see much wear in the upper groove where the cam pin has been putting pressure through thousands of rounds.
With that said, I have POF roller pins in all my AR's.
If you have been running the gun without a roller cam pin, your upper is probably already gouged. Once it reaches a certain wear point, it won't gouge it any more. However, the video brings up another point that the carrier key does use the inside track of the upper to keep the bolt unlocked while it strips the round. This really isn't a big deal if it is lubed. Look inside a DI gun that has been properly maintained and you won't see much wear in the upper groove where the cam pin has been putting pressure through thousands of rounds.
With that said, I have POF roller pins in all my AR's.
5/15/2012 2:49:17 PM
Originally Posted By wilkm21:
I have a POF rifle that has a standard Cam Pin. Should I upgrade it or leave it alone? Is it worth it?
I have a POF rifle that has a standard Cam Pin. Should I upgrade it or leave it alone? Is it worth it?
5/16/2012 8:56:32 PM
Originally Posted By Swat_dude:
Actually, the video misses the point of the roller cam pin and you need to know its purpose. In a DI gun, gas is directed inside the bolt carrier (it shits where it eats) and pushes on the bolt (the bolt rings trap the gas and this is in effect the piston-inside the bolt carrier!!). The gas pushes the bolt hard forward, sending the bolt carrier rearward. The other thing it does is force the cam pin all the way forward before the bolt starts its movement rearward. This fully aligns the cam pin behind the gas key for its rearward travel. In a piston gun, the op rod drives the carrier rearward. As the carrier is pushed rearward, the cam pin rides in its groove in the bolt carrier, turning the lugs to unlock the bolt. The second the bolt lugs clear the chamber lugs, the bolt begins its travel rearward. Depending on your guns design, the cam pin may or may not be fully aligned behind the gas key. When it is not fully aligned, this is the upper gouge occurs. An alternate solution to the roller cam would be to cut the grove in the bolt carrier precisely so the cam pin was fully behind the gas key when the lugs are freed but this would decrease reliability and require much tighter controls on where the chamber lugs wind up.
If you have been running the gun without a roller cam pin, your upper is probably already gouged. Once it reaches a certain wear point, it won't gouge it any more. However, the video brings up another point that the carrier key does use the inside track of the upper to keep the bolt unlocked while it strips the round. This really isn't a big deal if it is lubed. Look inside a DI gun that has been properly maintained and you won't see much wear in the upper groove where the cam pin has been putting pressure through thousands of rounds.
With that said, I have POF roller pins in all my AR's.
Actually, the video misses the point of the roller cam pin and you need to know its purpose. In a DI gun, gas is directed inside the bolt carrier (it shits where it eats) and pushes on the bolt (the bolt rings trap the gas and this is in effect the piston-inside the bolt carrier!!). The gas pushes the bolt hard forward, sending the bolt carrier rearward. The other thing it does is force the cam pin all the way forward before the bolt starts its movement rearward. This fully aligns the cam pin behind the gas key for its rearward travel. In a piston gun, the op rod drives the carrier rearward. As the carrier is pushed rearward, the cam pin rides in its groove in the bolt carrier, turning the lugs to unlock the bolt. The second the bolt lugs clear the chamber lugs, the bolt begins its travel rearward. Depending on your guns design, the cam pin may or may not be fully aligned behind the gas key. When it is not fully aligned, this is the upper gouge occurs. An alternate solution to the roller cam would be to cut the grove in the bolt carrier precisely so the cam pin was fully behind the gas key when the lugs are freed but this would decrease reliability and require much tighter controls on where the chamber lugs wind up.
If you have been running the gun without a roller cam pin, your upper is probably already gouged. Once it reaches a certain wear point, it won't gouge it any more. However, the video brings up another point that the carrier key does use the inside track of the upper to keep the bolt unlocked while it strips the round. This really isn't a big deal if it is lubed. Look inside a DI gun that has been properly maintained and you won't see much wear in the upper groove where the cam pin has been putting pressure through thousands of rounds.
With that said, I have POF roller pins in all my AR's.
Actually, the bolt in a DI and a piston gun start moving rearward at exactly the same rotation; when the lugs on the bolt line up with the slots in the barrel extension. Neither can move at all until they line up.
Joe
5/16/2012 9:03:49 PM
Originally Posted By scudzuki:
Actually, the bolt in a DI and a piston gun start moving rearward at exactly the same rotation; when the lugs on the bolt line up with the slots in the barrel extension. Neither can move at all until they line up.
Joe
Originally Posted By Swat_dude:
Actually, the video misses the point of the roller cam pin and you need to know its purpose. In a DI gun, gas is directed inside the bolt carrier (it shits where it eats) and pushes on the bolt (the bolt rings trap the gas and this is in effect the piston-inside the bolt carrier!!). The gas pushes the bolt hard forward, sending the bolt carrier rearward. The other thing it does is force the cam pin all the way forward before the bolt starts its movement rearward. This fully aligns the cam pin behind the gas key for its rearward travel. In a piston gun, the op rod drives the carrier rearward. As the carrier is pushed rearward, the cam pin rides in its groove in the bolt carrier, turning the lugs to unlock the bolt. The second the bolt lugs clear the chamber lugs, the bolt begins its travel rearward. Depending on your guns design, the cam pin may or may not be fully aligned behind the gas key. When it is not fully aligned, this is the upper gouge occurs. An alternate solution to the roller cam would be to cut the grove in the bolt carrier precisely so the cam pin was fully behind the gas key when the lugs are freed but this would decrease reliability and require much tighter controls on where the chamber lugs wind up.
If you have been running the gun without a roller cam pin, your upper is probably already gouged. Once it reaches a certain wear point, it won't gouge it any more. However, the video brings up another point that the carrier key does use the inside track of the upper to keep the bolt unlocked while it strips the round. This really isn't a big deal if it is lubed. Look inside a DI gun that has been properly maintained and you won't see much wear in the upper groove where the cam pin has been putting pressure through thousands of rounds.
With that said, I have POF roller pins in all my AR's.
Actually, the video misses the point of the roller cam pin and you need to know its purpose. In a DI gun, gas is directed inside the bolt carrier (it shits where it eats) and pushes on the bolt (the bolt rings trap the gas and this is in effect the piston-inside the bolt carrier!!). The gas pushes the bolt hard forward, sending the bolt carrier rearward. The other thing it does is force the cam pin all the way forward before the bolt starts its movement rearward. This fully aligns the cam pin behind the gas key for its rearward travel. In a piston gun, the op rod drives the carrier rearward. As the carrier is pushed rearward, the cam pin rides in its groove in the bolt carrier, turning the lugs to unlock the bolt. The second the bolt lugs clear the chamber lugs, the bolt begins its travel rearward. Depending on your guns design, the cam pin may or may not be fully aligned behind the gas key. When it is not fully aligned, this is the upper gouge occurs. An alternate solution to the roller cam would be to cut the grove in the bolt carrier precisely so the cam pin was fully behind the gas key when the lugs are freed but this would decrease reliability and require much tighter controls on where the chamber lugs wind up.
If you have been running the gun without a roller cam pin, your upper is probably already gouged. Once it reaches a certain wear point, it won't gouge it any more. However, the video brings up another point that the carrier key does use the inside track of the upper to keep the bolt unlocked while it strips the round. This really isn't a big deal if it is lubed. Look inside a DI gun that has been properly maintained and you won't see much wear in the upper groove where the cam pin has been putting pressure through thousands of rounds.
With that said, I have POF roller pins in all my AR's.
Actually, the bolt in a DI and a piston gun start moving rearward at exactly the same rotation; when the lugs on the bolt line up with the slots in the barrel extension. Neither can move at all until they line up.
Joe
Actually, in a DI gun, the gas is pushing on the bolt and extends it fully. This does not occur in a piston gun until the pin gouges into the upper and eventually lines up inside the upper groove.
5/16/2012 9:27:23 PM
Originally Posted By Swat_dude:
Actually, in a DI gun, the gas is pushing on the bolt and extends it fully. This does not occur in a piston gun until the pin gouges into the upper and eventually lines up inside the upper groove.
Originally Posted By scudzuki:
Actually, the bolt in a DI and a piston gun start moving rearward at exactly the same rotation; when the lugs on the bolt line up with the slots in the barrel extension. Neither can move at all until they line up.
Joe
Originally Posted By Swat_dude:
Actually, the video misses the point of the roller cam pin and you need to know its purpose. In a DI gun, gas is directed inside the bolt carrier (it shits where it eats) and pushes on the bolt (the bolt rings trap the gas and this is in effect the piston-inside the bolt carrier!!). The gas pushes the bolt hard forward, sending the bolt carrier rearward. The other thing it does is force the cam pin all the way forward before the bolt starts its movement rearward. This fully aligns the cam pin behind the gas key for its rearward travel. In a piston gun, the op rod drives the carrier rearward. As the carrier is pushed rearward, the cam pin rides in its groove in the bolt carrier, turning the lugs to unlock the bolt. The second the bolt lugs clear the chamber lugs, the bolt begins its travel rearward. Depending on your guns design, the cam pin may or may not be fully aligned behind the gas key. When it is not fully aligned, this is the upper gouge occurs. An alternate solution to the roller cam would be to cut the grove in the bolt carrier precisely so the cam pin was fully behind the gas key when the lugs are freed but this would decrease reliability and require much tighter controls on where the chamber lugs wind up.
If you have been running the gun without a roller cam pin, your upper is probably already gouged. Once it reaches a certain wear point, it won't gouge it any more. However, the video brings up another point that the carrier key does use the inside track of the upper to keep the bolt unlocked while it strips the round. This really isn't a big deal if it is lubed. Look inside a DI gun that has been properly maintained and you won't see much wear in the upper groove where the cam pin has been putting pressure through thousands of rounds.
With that said, I have POF roller pins in all my AR's.
Actually, the video misses the point of the roller cam pin and you need to know its purpose. In a DI gun, gas is directed inside the bolt carrier (it shits where it eats) and pushes on the bolt (the bolt rings trap the gas and this is in effect the piston-inside the bolt carrier!!). The gas pushes the bolt hard forward, sending the bolt carrier rearward. The other thing it does is force the cam pin all the way forward before the bolt starts its movement rearward. This fully aligns the cam pin behind the gas key for its rearward travel. In a piston gun, the op rod drives the carrier rearward. As the carrier is pushed rearward, the cam pin rides in its groove in the bolt carrier, turning the lugs to unlock the bolt. The second the bolt lugs clear the chamber lugs, the bolt begins its travel rearward. Depending on your guns design, the cam pin may or may not be fully aligned behind the gas key. When it is not fully aligned, this is the upper gouge occurs. An alternate solution to the roller cam would be to cut the grove in the bolt carrier precisely so the cam pin was fully behind the gas key when the lugs are freed but this would decrease reliability and require much tighter controls on where the chamber lugs wind up.
If you have been running the gun without a roller cam pin, your upper is probably already gouged. Once it reaches a certain wear point, it won't gouge it any more. However, the video brings up another point that the carrier key does use the inside track of the upper to keep the bolt unlocked while it strips the round. This really isn't a big deal if it is lubed. Look inside a DI gun that has been properly maintained and you won't see much wear in the upper groove where the cam pin has been putting pressure through thousands of rounds.
With that said, I have POF roller pins in all my AR's.
Actually, the bolt in a DI and a piston gun start moving rearward at exactly the same rotation; when the lugs on the bolt line up with the slots in the barrel extension. Neither can move at all until they line up.
Joe
Actually, in a DI gun, the gas is pushing on the bolt and extends it fully. This does not occur in a piston gun until the pin gouges into the upper and eventually lines up inside the upper groove.
The point of rotation where the bolt disengages from the barrel extension on my piston gun (Osprey conversion/BC) is exactly the limit of rotation imposed by the barrel cam slot in the BC.
Although the cam pin has not bottomed in the slot, it cannot rotate any further.
Also, I have the witness mark on the upper receiver in one of my DI guns.
It seems to be as much a factor of tolerance stackup as anything else.
Joe
5/17/2012 2:59:15 AM
Originally Posted By scudzuki:
The point of rotation where the bolt disengages from the barrel extension on my piston gun (Osprey conversion/BC) is exactly the limit of rotation imposed by the barrel cam slot in the BC.
Although the cam pin has not bottomed in the slot, it cannot rotate any further.
Also, I have the witness mark on the upper receiver in one of my DI guns.
It seems to be as much a factor of tolerance stackup as anything else.
Joe
Originally Posted By Swat_dude:
Actually, in a DI gun, the gas is pushing on the bolt and extends it fully. This does not occur in a piston gun until the pin gouges into the upper and eventually lines up inside the upper groove.
Originally Posted By scudzuki:
Actually, the bolt in a DI and a piston gun start moving rearward at exactly the same rotation; when the lugs on the bolt line up with the slots in the barrel extension. Neither can move at all until they line up.
Joe
Originally Posted By Swat_dude:
Actually, the video misses the point of the roller cam pin and you need to know its purpose. In a DI gun, gas is directed inside the bolt carrier (it shits where it eats) and pushes on the bolt (the bolt rings trap the gas and this is in effect the piston-inside the bolt carrier!!). The gas pushes the bolt hard forward, sending the bolt carrier rearward. The other thing it does is force the cam pin all the way forward before the bolt starts its movement rearward. This fully aligns the cam pin behind the gas key for its rearward travel. In a piston gun, the op rod drives the carrier rearward. As the carrier is pushed rearward, the cam pin rides in its groove in the bolt carrier, turning the lugs to unlock the bolt. The second the bolt lugs clear the chamber lugs, the bolt begins its travel rearward. Depending on your guns design, the cam pin may or may not be fully aligned behind the gas key. When it is not fully aligned, this is the upper gouge occurs. An alternate solution to the roller cam would be to cut the grove in the bolt carrier precisely so the cam pin was fully behind the gas key when the lugs are freed but this would decrease reliability and require much tighter controls on where the chamber lugs wind up.
If you have been running the gun without a roller cam pin, your upper is probably already gouged. Once it reaches a certain wear point, it won't gouge it any more. However, the video brings up another point that the carrier key does use the inside track of the upper to keep the bolt unlocked while it strips the round. This really isn't a big deal if it is lubed. Look inside a DI gun that has been properly maintained and you won't see much wear in the upper groove where the cam pin has been putting pressure through thousands of rounds.
With that said, I have POF roller pins in all my AR's.
Actually, the video misses the point of the roller cam pin and you need to know its purpose. In a DI gun, gas is directed inside the bolt carrier (it shits where it eats) and pushes on the bolt (the bolt rings trap the gas and this is in effect the piston-inside the bolt carrier!!). The gas pushes the bolt hard forward, sending the bolt carrier rearward. The other thing it does is force the cam pin all the way forward before the bolt starts its movement rearward. This fully aligns the cam pin behind the gas key for its rearward travel. In a piston gun, the op rod drives the carrier rearward. As the carrier is pushed rearward, the cam pin rides in its groove in the bolt carrier, turning the lugs to unlock the bolt. The second the bolt lugs clear the chamber lugs, the bolt begins its travel rearward. Depending on your guns design, the cam pin may or may not be fully aligned behind the gas key. When it is not fully aligned, this is the upper gouge occurs. An alternate solution to the roller cam would be to cut the grove in the bolt carrier precisely so the cam pin was fully behind the gas key when the lugs are freed but this would decrease reliability and require much tighter controls on where the chamber lugs wind up.
If you have been running the gun without a roller cam pin, your upper is probably already gouged. Once it reaches a certain wear point, it won't gouge it any more. However, the video brings up another point that the carrier key does use the inside track of the upper to keep the bolt unlocked while it strips the round. This really isn't a big deal if it is lubed. Look inside a DI gun that has been properly maintained and you won't see much wear in the upper groove where the cam pin has been putting pressure through thousands of rounds.
With that said, I have POF roller pins in all my AR's.
Actually, the bolt in a DI and a piston gun start moving rearward at exactly the same rotation; when the lugs on the bolt line up with the slots in the barrel extension. Neither can move at all until they line up.
Joe
Actually, in a DI gun, the gas is pushing on the bolt and extends it fully. This does not occur in a piston gun until the pin gouges into the upper and eventually lines up inside the upper groove.
The point of rotation where the bolt disengages from the barrel extension on my piston gun (Osprey conversion/BC) is exactly the limit of rotation imposed by the barrel cam slot in the BC.
Although the cam pin has not bottomed in the slot, it cannot rotate any further.
Also, I have the witness mark on the upper receiver in one of my DI guns.
It seems to be as much a factor of tolerance stackup as anything else.
Joe
I'm not saying it can't happen in a DI gun, but the problem is exasperated by piston op rod operation. I have 3 different piston AR's and all have it to some degree.
5/17/2012 1:48:02 PM
5/19/2012 1:50:00 AM
To SWAT dude I use a roller cam pin in my Osprey416 short stroke piston and that was on a new upper it left the same gouge on the inside of the upper the cam pin would also tried the DI carrier roller cam pin did the same thing,once you get the dent its worn in and wont go any further also you can radius the top of the cam pin more rounded than square and get the same dent as the roller cam,in my tests on new upper DI or piston rod with a roller pin and you still get the gouge although a smoother gouge with the roller and also a smoothe gouge with modified standard pin...yea I tried that too..easy mod at 1/4 the cost of the roller cam pin.
5/19/2012 11:43:35 AM
Originally Posted By Swat_dude:
I'm not saying it can't happen in a DI gun, but the problem is exasperated by piston op rod operation. I have 3 different piston AR's and all have it to some degree.
Originally Posted By scudzuki:
The point of rotation where the bolt disengages from the barrel extension on my piston gun (Osprey conversion/BC) is exactly the limit of rotation imposed by the barrel cam slot in the BC.
Although the cam pin has not bottomed in the slot, it cannot rotate any further.
Also, I have the witness mark on the upper receiver in one of my DI guns.
It seems to be as much a factor of tolerance stackup as anything else.
Joe
Originally Posted By Swat_dude:
Actually, in a DI gun, the gas is pushing on the bolt and extends it fully. This does not occur in a piston gun until the pin gouges into the upper and eventually lines up inside the upper groove.
Originally Posted By scudzuki:
Actually, the bolt in a DI and a piston gun start moving rearward at exactly the same rotation; when the lugs on the bolt line up with the slots in the barrel extension. Neither can move at all until they line up.
Joe
Originally Posted By Swat_dude:
Actually, the video misses the point of the roller cam pin and you need to know its purpose. In a DI gun, gas is directed inside the bolt carrier (it shits where it eats) and pushes on the bolt (the bolt rings trap the gas and this is in effect the piston-inside the bolt carrier!!). The gas pushes the bolt hard forward, sending the bolt carrier rearward. The other thing it does is force the cam pin all the way forward before the bolt starts its movement rearward. This fully aligns the cam pin behind the gas key for its rearward travel. In a piston gun, the op rod drives the carrier rearward. As the carrier is pushed rearward, the cam pin rides in its groove in the bolt carrier, turning the lugs to unlock the bolt. The second the bolt lugs clear the chamber lugs, the bolt begins its travel rearward. Depending on your guns design, the cam pin may or may not be fully aligned behind the gas key. When it is not fully aligned, this is the upper gouge occurs. An alternate solution to the roller cam would be to cut the grove in the bolt carrier precisely so the cam pin was fully behind the gas key when the lugs are freed but this would decrease reliability and require much tighter controls on where the chamber lugs wind up.
If you have been running the gun without a roller cam pin, your upper is probably already gouged. Once it reaches a certain wear point, it won't gouge it any more. However, the video brings up another point that the carrier key does use the inside track of the upper to keep the bolt unlocked while it strips the round. This really isn't a big deal if it is lubed. Look inside a DI gun that has been properly maintained and you won't see much wear in the upper groove where the cam pin has been putting pressure through thousands of rounds.
With that said, I have POF roller pins in all my AR's.
Actually, the video misses the point of the roller cam pin and you need to know its purpose. In a DI gun, gas is directed inside the bolt carrier (it shits where it eats) and pushes on the bolt (the bolt rings trap the gas and this is in effect the piston-inside the bolt carrier!!). The gas pushes the bolt hard forward, sending the bolt carrier rearward. The other thing it does is force the cam pin all the way forward before the bolt starts its movement rearward. This fully aligns the cam pin behind the gas key for its rearward travel. In a piston gun, the op rod drives the carrier rearward. As the carrier is pushed rearward, the cam pin rides in its groove in the bolt carrier, turning the lugs to unlock the bolt. The second the bolt lugs clear the chamber lugs, the bolt begins its travel rearward. Depending on your guns design, the cam pin may or may not be fully aligned behind the gas key. When it is not fully aligned, this is the upper gouge occurs. An alternate solution to the roller cam would be to cut the grove in the bolt carrier precisely so the cam pin was fully behind the gas key when the lugs are freed but this would decrease reliability and require much tighter controls on where the chamber lugs wind up.
If you have been running the gun without a roller cam pin, your upper is probably already gouged. Once it reaches a certain wear point, it won't gouge it any more. However, the video brings up another point that the carrier key does use the inside track of the upper to keep the bolt unlocked while it strips the round. This really isn't a big deal if it is lubed. Look inside a DI gun that has been properly maintained and you won't see much wear in the upper groove where the cam pin has been putting pressure through thousands of rounds.
With that said, I have POF roller pins in all my AR's.
Actually, the bolt in a DI and a piston gun start moving rearward at exactly the same rotation; when the lugs on the bolt line up with the slots in the barrel extension. Neither can move at all until they line up.
Joe
Actually, in a DI gun, the gas is pushing on the bolt and extends it fully. This does not occur in a piston gun until the pin gouges into the upper and eventually lines up inside the upper groove.
The point of rotation where the bolt disengages from the barrel extension on my piston gun (Osprey conversion/BC) is exactly the limit of rotation imposed by the barrel cam slot in the BC.
Although the cam pin has not bottomed in the slot, it cannot rotate any further.
Also, I have the witness mark on the upper receiver in one of my DI guns.
It seems to be as much a factor of tolerance stackup as anything else.
Joe
I'm not saying it can't happen in a DI gun, but the problem is exasperated by piston op rod operation. I have 3 different piston AR's and all have it to some degree.
Interesting.
I suspect that the force required to extract the round effectively bottoms the cam pin in the BC cam slot on a piston gun, just like it is bottomed on a DI gun.
I don't see it as a problem regardless, as others have pointed out, it wears to a point then stops.
Just like carrier tilt, it's not an issue unless you are hyper sensitive to how much aluminum is exposed by witness marks inside your AR receivers.
Joe
5/19/2012 1:11:34 PM
Originally Posted By scudzuki:
Interesting.
I suspect that the force required to extract the round effectively bottoms the cam pin in the BC cam slot on a piston gun, just like it is bottomed on a DI gun.
I don't see it as a problem regardless, as others have pointed out, it wears to a point then stops.
Just like carrier tilt, it's not an issue unless you are hyper sensitive to how much aluminum is exposed by witness marks inside your AR receivers.
Joe
Originally Posted By Swat_dude:
I'm not saying it can't happen in a DI gun, but the problem is exasperated by piston op rod operation. I have 3 different piston AR's and all have it to some degree.
Originally Posted By scudzuki:
The point of rotation where the bolt disengages from the barrel extension on my piston gun (Osprey conversion/BC) is exactly the limit of rotation imposed by the barrel cam slot in the BC.
Although the cam pin has not bottomed in the slot, it cannot rotate any further.
Also, I have the witness mark on the upper receiver in one of my DI guns.
It seems to be as much a factor of tolerance stackup as anything else.
Joe
Originally Posted By Swat_dude:
Actually, in a DI gun, the gas is pushing on the bolt and extends it fully. This does not occur in a piston gun until the pin gouges into the upper and eventually lines up inside the upper groove.
Originally Posted By scudzuki:
Actually, the bolt in a DI and a piston gun start moving rearward at exactly the same rotation; when the lugs on the bolt line up with the slots in the barrel extension. Neither can move at all until they line up.
Joe
Originally Posted By Swat_dude:
Actually, the video misses the point of the roller cam pin and you need to know its purpose. In a DI gun, gas is directed inside the bolt carrier (it shits where it eats) and pushes on the bolt (the bolt rings trap the gas and this is in effect the piston-inside the bolt carrier!!). The gas pushes the bolt hard forward, sending the bolt carrier rearward. The other thing it does is force the cam pin all the way forward before the bolt starts its movement rearward. This fully aligns the cam pin behind the gas key for its rearward travel. In a piston gun, the op rod drives the carrier rearward. As the carrier is pushed rearward, the cam pin rides in its groove in the bolt carrier, turning the lugs to unlock the bolt. The second the bolt lugs clear the chamber lugs, the bolt begins its travel rearward. Depending on your guns design, the cam pin may or may not be fully aligned behind the gas key. When it is not fully aligned, this is the upper gouge occurs. An alternate solution to the roller cam would be to cut the grove in the bolt carrier precisely so the cam pin was fully behind the gas key when the lugs are freed but this would decrease reliability and require much tighter controls on where the chamber lugs wind up.
If you have been running the gun without a roller cam pin, your upper is probably already gouged. Once it reaches a certain wear point, it won't gouge it any more. However, the video brings up another point that the carrier key does use the inside track of the upper to keep the bolt unlocked while it strips the round. This really isn't a big deal if it is lubed. Look inside a DI gun that has been properly maintained and you won't see much wear in the upper groove where the cam pin has been putting pressure through thousands of rounds.
With that said, I have POF roller pins in all my AR's.
Actually, the video misses the point of the roller cam pin and you need to know its purpose. In a DI gun, gas is directed inside the bolt carrier (it shits where it eats) and pushes on the bolt (the bolt rings trap the gas and this is in effect the piston-inside the bolt carrier!!). The gas pushes the bolt hard forward, sending the bolt carrier rearward. The other thing it does is force the cam pin all the way forward before the bolt starts its movement rearward. This fully aligns the cam pin behind the gas key for its rearward travel. In a piston gun, the op rod drives the carrier rearward. As the carrier is pushed rearward, the cam pin rides in its groove in the bolt carrier, turning the lugs to unlock the bolt. The second the bolt lugs clear the chamber lugs, the bolt begins its travel rearward. Depending on your guns design, the cam pin may or may not be fully aligned behind the gas key. When it is not fully aligned, this is the upper gouge occurs. An alternate solution to the roller cam would be to cut the grove in the bolt carrier precisely so the cam pin was fully behind the gas key when the lugs are freed but this would decrease reliability and require much tighter controls on where the chamber lugs wind up.
If you have been running the gun without a roller cam pin, your upper is probably already gouged. Once it reaches a certain wear point, it won't gouge it any more. However, the video brings up another point that the carrier key does use the inside track of the upper to keep the bolt unlocked while it strips the round. This really isn't a big deal if it is lubed. Look inside a DI gun that has been properly maintained and you won't see much wear in the upper groove where the cam pin has been putting pressure through thousands of rounds.
With that said, I have POF roller pins in all my AR's.
Actually, the bolt in a DI and a piston gun start moving rearward at exactly the same rotation; when the lugs on the bolt line up with the slots in the barrel extension. Neither can move at all until they line up.
Joe
Actually, in a DI gun, the gas is pushing on the bolt and extends it fully. This does not occur in a piston gun until the pin gouges into the upper and eventually lines up inside the upper groove.
The point of rotation where the bolt disengages from the barrel extension on my piston gun (Osprey conversion/BC) is exactly the limit of rotation imposed by the barrel cam slot in the BC.
Although the cam pin has not bottomed in the slot, it cannot rotate any further.
Also, I have the witness mark on the upper receiver in one of my DI guns.
It seems to be as much a factor of tolerance stackup as anything else.
Joe
I'm not saying it can't happen in a DI gun, but the problem is exasperated by piston op rod operation. I have 3 different piston AR's and all have it to some degree.
Interesting.
I suspect that the force required to extract the round effectively bottoms the cam pin in the BC cam slot on a piston gun, just like it is bottomed on a DI gun.
I don't see it as a problem regardless, as others have pointed out, it wears to a point then stops.
Just like carrier tilt, it's not an issue unless you are hyper sensitive to how much aluminum is exposed by witness marks inside your AR receivers.
Joe
for the most part it does wear to a point then stop.
the reason for the roller cam pin was because in certain Piston rifles that used a standard bolt without the gas rings when going to strip a round from the magazine the bolt would be shoved back and the cam pin would grind the upper.
on these rifles after a few thousand rounds the upper would start to be gouged and eventually ruin the upper, so POF made the roller cam pin to fix this.
now in rifles that have springs and specifically made bolts this is not an issue
