Just wanted to report success in making my first 300 Whisper barrel. I picked up a .30 cal blank from Midway and called up PTG and purchased a chamber reamer and a set of headspace gauges. I turned a 7.5" barrel for my M16. My goal was to get a heavy-hitting subgun-class round with a low cyclic rate in the '16. Well, 200 grain Sierra MatchKings in the 300 Whisper platform certainly fits the bill, with a muzzle velocity of 1040 fps and an IPSC power factor of 208.
I used a JP adjustable gas block for this first one but it turns out I got the gas port dimension just right, so I don't think I'll need an adjustable block anymore unless I decide to go supersonic with this upper.
So far (about 100 rounds) the package is very reliable in both semi and FA modes.
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