
Originally Posted by
K.L. Davis
Okay... this is how it happened.
In 1986, I started playing with different barrel/gas system lengths... finally, about 10 years or so ago, I took several barrels and started drilling and welding gas ports... cutting barrels back... opening gas ports... and measuring pressure at the gas port in every configuration I could - I ended up with pressures and lock times for 22, 20, 18, 17, 16, 15.7, 15.5, 15, 14.5, 13, 12.5, 12, 11.5, 11.5, 10.5, 10.3, 10, 9, 8, 7.5 and 7 inch barrels with gas ports on each barrel starting at ~2" from the muzzle and every inch back to ~5" from the chamber.
During this testing, the freeze test was done on a lot of the guns that seemed to work good... of course a great many of the test configurations were not even worth trying to get to run.
The 16" Middy is the ideal carbine (my opinion), when properly built from good parts, it runs like a clock.
Systems that fail are pretty predictable... I wrote this in another thread - but it is to the point:
The only real important pressure is the max/operating pressure inside of the BCG - that pressure is a function of the following:
Gas Pressure at the port
Port Size
Barrel diameter
Time the pressure stays high (dwell)
Lock Time - the time the BCG remains locked, while pressure is allowed to build
But yes, dwell time is one of the most contributing factors.
Eric D nailed it pretty well... if you have a proven configuration that runs well at 70* - I would not worry about temps dropping to the teens... the only time I would even factor that in would be making a cold rifle/ammo shot at long range...
The bottom line is this: systems that work are the ones people stick with, but often you get some weird or even retarded designs from the "can't make it better, make it different" crowd - if you are looking at a barrel and gas system combination that you have never heard of... it might be worth asking around to see what others think. M4C has more than a few folks that are able to tell chicken shit from chicken salad.
Bookmarks