So, I sent a few rounds over the Pact Professional just for kicks.  

Gun 1: AR-15 Colt 16" 1/7 with Phantom FH.
Gun 2: Ruger 6" Mark II semi-auto handgun.

Ammo 1: 40gr Winchester Dynapoint bulk pack from Wally Mart
Ammo 2: 36gr Federal HV bulk 550 pack from Wally Mart

Results:
Dynapoint in AR-15 ==== 1080 fps
Dynapoint in Ruger ===== 980 fps
Federal in AR-15 ====== 1180 fps
Federal in Ruger ======= 1100 fps

Environment:
40*F air temp
4750' Elevation

Discussion:
So, the Dynapoint in the AR-15 is averaging just under the speed of sound in the test conditions (SoS at 40*F = 1096 fps).  Some will be breaking it and others will definitely be subsonic.  Accuracy of the Dynapoint at 100yds in the 1/7 barrel was exceptional, staying well within an 8.5x11" sheet of paper using only an Eotech for sighting.  It would hit soda cans at 50yds every time.

Thanks for the great info - how is cycling reliability with these rounds?

Do you also have any tips for tweaking the M261 kit, as I'm having cycling problems with standard and high-velocity ammo.  The only ammo that functions more or less reliably is the hypervelocity CCI Velocitor, which is quite a bit more expensive than "regular" .22 LR ammo.

Quoted: Thanks for the great info - how is cycling reliability with these rounds? Do you also have any tips for tweaking the M261 kit, as I'm having cycling problems with standard and high-velocity ammo.  The only ammo that functions more or less reliably is the hypervelocity CCI Velocitor, which is quite a bit more expensive than "regular" .22 LR ammo.

Gabe,

Maybe I'm just lucky because  I have used all kinds of ammo on my  2 M261 kits and I never had any problems.  Try using the Winchester Dynapoints since almost everybody here have good results with them.  I can send you pics of my set up if you want.

I've now shot three or four thousand rounds of Dynapoints in temperatures from the 40s to the 90s, and in barrels from 16" to 26" and I can tell you that they are normally subsonic. Every now and then, one cracks, though. I've had maybe somewhere around a dozen or so make the supersonic crack. Oddly enough, these don't seem to produce flyers--at least I've never been able to look at a target and say, "Oh, yeah, THAT must have been that loud one."

Other kinds of ammo are normally supersonic but will occasionally throw one that isn't. And then there is ammo that will make three or even four different kinds of sounds from the same box. I don't buy more than one box of anything that does THAT.

Quoted: Thanks for the great info - how is cycling reliability with these rounds? Do you also have any tips for tweaking the M261 kit, as I'm having cycling problems with standard and high-velocity ammo.  The only ammo that functions more or less reliably is the hypervelocity CCI Velocitor, which is quite a bit more expensive than "regular" .22 LR ammo.

Great reliability.  Went through 500rds last week and got 2 malfunctions.  You have to keep all sliding surfaces wet with oil/lube.  Once you get it running, I wouldn't put any more "hot" or high velocity ammo through it, just because the mechanism was not designed for it, and will certainly hasten a part breakage.  Make sure the mag inserts are properly seated --- it's easy to "jam" them in and get the wrong angle for feeding.