I finally got my 308 back from the smith where it was getting treaded for the QD flash hider for the YHM Phantom 762 sound suppressor.  The can is still with the dealer, but I got the rifle to the range Friday night to test for any accuracy change due to threaded/recrowned barrel and/or addition of the flash hider.  It was grouping in the 1/2-3/4 MOA range with and without the flash hider, which is consistent with pre-threading groups.  There seemed to be about a 3/4 MOA shift right and 1/2 down with the flash hider installed.

On Saturday I met up with my SOT for a conjugal visit.  We didn't get to print groups on paper, but we fired several rounds through the 700.  I haven't heard very many 308 cans and we didn't have any other to test side-by-side with, but he felt it was one of the better ones he'd heard.  He named a couple that he thought it outperformed, but I'd prefer to hear them side by side before I publicly repeat his claim.

Next I attached it to an M16 w/ 11.5" barrel and ran through a mag, then did the same with the YHM 556 can for comparison.  They sounded roughly the same, but for some strange reason the rate of fire seemed much slower with the 762 can than with the 556 can.  I never would have expected that.

I'm hoping to have the F4 back in the next week or so.  Hopefully I will have more to report then.

Consider the silencer a restriction to the exit of gas causing backpressure.

.223 much restriction more gas forced into the gas operated recoil system faster rate of fire.

.308 less restriction less gas forced into the gas operated recoil system slower rate of fire.

If you shoot the gun left handed you should also notice less gas in the faces since blowback is not as much with the looser higher volume silencer.

Makes perfect sense.  I'd just never really thought about it.  It actually seemed slower than it does unsupressed, though, which surprised me (though I didn't run a mag through it unsurpressed that day to compare).  I'll have to check that out next time.  If that's the case, maybe it's a case of increased pressure causing the bolt to want to unlock while the case is still pressurized againse the chamber wall, causing the bolt to slow down.  Pressure curves can do crazy things.