The ULTIMATE just got even better! My 18" GI profile CHF FN barrel has arrived and cold weather testing has completed! You're getting the same ballistic performance with the 18" barrel, same sight radius, etc in a lighter and more maneuverable package! The 20" barrel assembly will be going up for sale soon! Check it out!
COLD WEATHER TESTING RANGE REPORT
Photo of the completed rifle (clamp on FSB used temporarily for testing)
My 18" GI profile, CHF FN 1-7 twist barrel finally arrived at my gunsmith's yesterday, just in time for some cold weather testing.
The weather was very cooperative with my concerns for testing, even though we are heading towards spring and things are gradually getting warmer, there was a recent swell of arctic cold weather air this past week and temps have been in the single digits. Temps actually went down to -11 last night and are still single digits today. The upper was assembled with the barrel yesterday after it arrived. After all of my research I wanted Braceman (my smith) to start off with a .1015 gas port (Irwin drill bit size #38), see if it would cycle tula and herters steel cased ammo (the worst crap we could find) in the cold and then go from there. Good thing we drilled out the gas port, because the barrel actually arrived with an undersized port! Port size was .089, and standard for a 20" barrel is .093, and even that is too small for an all purpose 18" barreled rifle gassed gun!
The gas port was drilled out to .1015, the barrel was installed, and then it was left to sit out in the barn all night in -11 degree F temperature along with the tula and herters steel cased test ammo! It was a cold rifle!!
Upper was installed on a standard A2 lower with standard rifle buffer / spring and was test fired in the morning shortly after day break. Actual temperature during test fire was only 2 degrees! A crappy tapco polymer mag was used for testing, as was an old dirty M16 full auto BCG. The BCG and gun were completely dry and unlubed. Braceman fired 10 rounds of steel cased herters .223 and 10 rounds of steel cased tula .223 consecutively. The gun cycled flawlessly and locked the bolt back after the last round, the steel casings were ejected around 6 ft away at 3 o'clock.
The recoil was light and the cycle was smooth due to the low powered ammo.
Braceman informed me that as things in the rifle "carboned up" over time through firing, they would only get a better gas seal and cycle even more positively. At this point, I am going to call testing complete. If a newly assembled gun can cycle the worst steel case ammo around reliably and smoothly with NO LUBE after sitting in -11 degree weather, I don't see the need to open up the gas port anymore. I don't see this rifle NOT cycling reliably with any ammo under any conditions, esp after it carbons up and breaks in.
.102 is, in my opinion, optimal gas port size for my purposes with an 18" rifled gas barrel.