Not saying your wrong, just never heard of it.
Printable View
I bet it's negligible... but I could see how a full profiled barrel would absorb more heat and have the potential for a slight reduction in port errosion.
I've always been curious about this too.
What wears faster?
.625" @ gas port or .750" @ gas port?
Assuming same ammo, rate of fire, etc...
Given that the gas port and gas block functional assembly is the same for each barrel profile, they should have similar erosion rates. It should be noted that not all gas ports are the same size and smaller ports should exhibit higher gas velocities and thus slightly faster erosion. Even though the material removal rates may be similar, a gov't profile barrel has a .0625" wear advantage on a pencil barrel, so it will last longer.
There would probably be less erosion if the port was finished with a slight countersink or radius, but that would add an extra machining operation.
-Hold the phone- are we talking erosion within the bore or at the gas block to barrel interface?
I appeciate the thoughtful replies and discussion. SMT85 has me right...and I was mainly wondering about any erosion difference on the bore side of the port between .625" barrels and .750" barrels of the same length. It sounds like it should be negligible in the grand scheme, with throat erosion maybe even negating the concern at that high of a round count.
Also, anyone know if port diameters vary between .625" and .750" barrels with the same length and port location?
ETA: I sincerely apologize to the board and to MistWolf for my behavior...we have enough enemies lately without fighting amongst ourselves over the trivial stuff, and I'm sorry I engaged on that level.
Being in the profession I Was in,,,how much erosion will cause a failure and what will erosion cause? Higher operating [bolt] pressure or will the erosion cause accuracy problems from barrel wear in the area? Guns are a machine and machines wear out and "hopefully not" break.
SteveS - Check out the video link in this thread that Magic referred to:
http://m4carbine.net/showthread.php?...light=40%2C000
Although this was more indicative of a torture-test case than a long-term use case, I was pretty surprised by the visible amount of gas port erosion that these 10K barrels exhibited.
Your question is a really good one though, if I understand it - would gas port erosion start to affect reliability before throat erosion ever would? We know throat erosion can ruin barrel accuracy, but how long will the weapon keep firing reliably until gas port erosion gets the best of it, and reliability is affected?