My 4th 300 Whisper attempt

[ikorman]

Folks,

I have been trying (successfully and unsuccessfully) to setup a 300 Whisper platform. First one was some parts thrown together by Model1Sales for an AR upper. None of it worked. Second was a partial success story, using a switch-barrel Remington 700 also chambered in 223 and 17Mach4. I did not need the other two barrels and didn't want to keep 2 more scopes so I sold the whole thing.

Third attempt was a good one, albeit somewhat expensive: a local smith botched up a Rem700 rebarreling to 300 Whisper and I had to bring it to another smith that made it perfect. The gun came out sweet but I paid twice. Whatever! I am getting 1/2 minute groups with 220gr subsonic load and my YHM 30-cal can.

The last one: I had a couple of questions about it. I bought a used SSK Industries AR15 upper, 20-inch, A1 carry handle with the special adjustible gas thingie. I shot it today and had some mixed results: at first, it would not cycle so I cranked the the gas port all the wat up and it would eject brass but would not load the next round with 220gr subsonic load. I guess this was a short-stroke?

When I finally thought I should try it with a silencer for more gas pressure, it started behaving slightly better but not 100%. It would sometimes short-stroke and sometimes would do everything right, intermittenly.

Finally, I tried a 150gr 2100fps load and it worked pretty well. With the can and the gas port, it would cycle almost every time.

I really want to use the 220gr subsonic load. Otherwise, whats the point of 300 Whisper?

What am I missing? What should I do here? This setup seems to work much better than my first AR attempt and I don't want to write it off. AR15 in 300 whisper is too much fun to pass up.