Low pressure cycling of the AR10

Donald ........

You've received a lot of very good information in these replies. Using subsonic loads in a 308 will leave you with MAJOR disadvantages compared to building a 300 Whisper on an AR-15.

However, if you're determined to make your 308 subsonic anyway, forget about using 220 grain bullets. At subsonic velocity, they won't shoot well at all without at least 1-8 twist rifling, and if you're shooting lightweight bullets (and staying subsonic), you're loosing way too much power.

Weakening the recoil spring not an option, because you'll need the same force to feed rounds from your magazine. You'll need to open up the gas port quite a bit, and add an adjustable gas block (like the one J.D. Jones builds). It's an easy project, but I'd never waste a good AR-10 on such a poor performing rifle.

- Innovative
 
The case being used in this AR10 is the full sized 308. It is loaded to less than 1100 fps by using about 8 grains of Trailboss powder with the 170 grain bullet. I broke one of the rounds down and weighed the components. The load of Trailboss comes about 2/3 up in the case. Therefore there is no sonic crack from the bullet and the suppressor takes care of the muzzle blast. He may just have to use it as is and cycle it my hand. Thanks anyway guys. I have put him in touch with SSK Industries that builds the Whisper line of cartridges.

Donald

The rifle in question does not belong to me. It belongs to a friend and he already has a load ( see above ). It does shoot, how accurate I don't know but he is satisfied with it except the cycling. I have put him in touch with eveyone I can think of, so it is out of my hands now. Thanks for all the suggestions.

Donald
 
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