Guys, anyone that might help, please, I have an AR15 with a .300 Whisper upper. I have played around with various powders and trying to get the gun to both cycle as it should and also stay subsonic.

Anyone wioth advice on loads??

Presently the latest load is 9.5 grains of H110 and 180 and 190 grain bullets.
This load is subsonic however, the bolt will cycle enough to eject but not far enough back to pick up another round.

i will keep playing with it but hope perhaps someone may have experience with this same thing/round.

Thanks

Where is the gas port?

at the end of the barrel. just a standard ar design.

I would suggest a heavier bullet. Please correct me If I am wrong, aren't they designed to work with really heavy bullets? Isn't there like a 300 gr bullet made specially for these things?

i was going to try that later today...same charge but with 200 and 220 grain bullets.

Check your PMs...

It was designed around the 240 gr Sierra Match King. You can probably find a lot of help on AR15.com. The intent acording to conversation I had with Jones many years ago was to have the twist rate just so that the 240 SMK was just stable enough to fly straight but unstable enough to tumble on impact. The long bullet causes a lot of tissue damage tumbling through an animal. And it won't fly fast enough to mushroom. So twist rate is important for the subsonics.

But then I guess a lot could have evolved since that conversation.

Brownells sells a gas tube with a valve on top of it. You may need to drill a hole through the top of your free float tube or hand guard. You can adjust the amount of gas flow with an Allen head wrench.

Noveske, via Brownells sells a gas block with an easy to turn dial for adjusting flow. You need a 1:8" twist to stabilize the 240-grain bullets.

Kind of the idea with the round in a military setting is to shut the gas off, turn the sentry's head into a bird bath, and then cycle the action by hand (i.e. quietly). The other method of employment for relatively close in work with a bunch of "us" versus a bunch of "them" is to give 'er the gas, go to full auto on the happy switch and use the suppressor to mitigate the boom, boom part. "Them" do not even hear a sonic crack, just an action going clackety-clack; somewhere. As they say, "it doesn't make you silent, it makes you invisible."

Cutting down the spring an inch can help, so can taking weight out of the buffer. I do this for my subsonic 458 socom.

My SSK 300 whisper upper has the gas port located much closer to the action then the typical carbine setup. It cycles with any subsonic load 150 grains and heavier.

Ranb