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SERPENT5XX · 08-07-2005, 20:57

Gene,

The breaks both occurred on the previously installed conventional direct gas uppers.

If I remember correctly they both occurred while at Mid-South Institute of Self-defense Shooting (MISS). There are several ranges at MISS where the potential to fire many rounds of ammo exists while completing the course of fire. I have also seen several M4's break in comparable ways over the years in Kuwait while doing CQB flat range training. This mostly happened in the summer months due to the ambient air temperature along with the high round count drills. This high rate of fire was often more than the conventional M4 type gas system could endure. (We tried to fix this by going with the heavier profile M4 barrel)

Anyway when you fire a conventional M4 type upper hot gases are funneled from the barrel through the gas tube and into the gas key on the bolt carrier group. This is what causes the gun to cycle. These hot gasses make the bolt and bolt carrier very hot. Heat, or more importantly the constant heating and cooling of metal causes it to fail long before it would if it was not subject to that abusive environment.

Next time you go to the range shoot a couple of mags through your M4, then pull out the bolt carrier group and hold it in your hand....ouch!! Now do it with a piston driven upper. I have fired 3-4 mags as fast as I could pull the trigger on my POF gun and then pulled the bolt carrier out....barely warm. I could hold it to my face. Also there was a significant lack of carbon crud on the POF bolt for the same reason.

This lack of carbon and heat in the POF gun is because the piston system does not spray hot gas directly into the chamber to run the gun.

Are you familiar with the FN FAL? It uses a similar method. I believe that this lack of hot gas being sent directly into the chamber will lead to an extended weapon life as well as added reliability in the piston systems. POF, HK, what ever M4 type weapon with this system will have this benefit inherently due to the system of operation, brand name aside.

I hope this clarifies my post for you.

Thanks,

SERPENT5XX

08-07-2005, 20:57	#14
SERPENT5XX Quiet Professional Join Date: Apr 2004 Location: On the road Posts: 105	Gene, The breaks both occurred on the previously installed conventional direct gas uppers. If I remember correctly they both occurred while at Mid-South Institute of Self-defense Shooting (MISS). There are several ranges at MISS where the potential to fire many rounds of ammo exists while completing the course of fire. I have also seen several M4's break in comparable ways over the years in Kuwait while doing CQB flat range training. This mostly happened in the summer months due to the ambient air temperature along with the high round count drills. This high rate of fire was often more than the conventional M4 type gas system could endure. (We tried to fix this by going with the heavier profile M4 barrel) Anyway when you fire a conventional M4 type upper hot gases are funneled from the barrel through the gas tube and into the gas key on the bolt carrier group. This is what causes the gun to cycle. These hot gasses make the bolt and bolt carrier very hot. Heat, or more importantly the constant heating and cooling of metal causes it to fail long before it would if it was not subject to that abusive environment. Next time you go to the range shoot a couple of mags through your M4, then pull out the bolt carrier group and hold it in your hand....ouch!! Now do it with a piston driven upper. I have fired 3-4 mags as fast as I could pull the trigger on my POF gun and then pulled the bolt carrier out....barely warm. I could hold it to my face. Also there was a significant lack of carbon crud on the POF bolt for the same reason. This lack of carbon and heat in the POF gun is because the piston system does not spray hot gas directly into the chamber to run the gun. Are you familiar with the FN FAL? It uses a similar method. I believe that this lack of hot gas being sent directly into the chamber will lead to an extended weapon life as well as added reliability in the piston systems. POF, HK, what ever M4 type weapon with this system will have this benefit inherently due to the system of operation, brand name aside. I hope this clarifies my post for you. Thanks, SERPENT5XX
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