Originally Posted by
E-man930
I agree with you motoduck, I'm not trying to bash KAC either but it they did enlarge their gas ports on the current SR-15 offerings compared to the original SR-15 carbines they originally released. I'm not sure how that translates to the SBR uppers but I was disappointed to say the least. I guess they got tired of fielding calls from folks saying their new rifle won't cycle .223 reliably...
My SBR's recoil impulse with the H2 KAC buffer and Colt carbine spring was really violent and created brass ejection issues where the brass would not get clear of the ejection port and tumble back in locking the gun up. I have since tried a Tubbs CS FW spring and the H2 combo (same result), and an H&K 416 "red stripe" spring and the H2 combo which resulted in no malfunctions but the brass ejection pattern was slightly erratic around 1:30-2:00. Yesterday, I tested a BCM H3 buffer along with the H&K spring and I think I found a sweet spot with my setup. The H3 buffer helped the rifle eject the brass another few feet further than the H2 and all of it was dead on at 2:00. You could probably have caught most of it with a cup so I am happy my ejection issues are solved. The combo also shoots incredibly soft and smooth, and combined with my LMT enhanced carrier, functions 100% with and without the can. I loaded about 10 rounds (I know it's a small sample for now) of XM193 one at a time in a Pmag and tested for the bolt to lock back, which it did every time both with and without the can. I also tested some random .223 ammo and it locked the bolt back with the can but not without; although it would cycle and feed without it. I put about 180-190 rounds through the current setup suppressed and had zero issues. I have decided to just keep it setup this way and put another 800-850 rounds (want to hit 1000 round mark suppressed) through it without cleaning it to see how reliable it will be going forward.
My buddy has since ordered an H3 and BCM carbine spring for his SR15 and he intends to test his setup with a Tubbs CS spring, H&K 416 red stripe spring, and an H&K 416 tungsten buffer in addition to the H3 and BCM spring to see what works best. He is not running an enhanced LMT carrier so it will be interesting to see what works 100% in his gun. Thanks again everyone for the advice, I may break down and pickup an A5 setup / LMT SOPMOD stock one day just to see how tangible the difference is over my current franken-setup.