Umm..no.
Umm..no.
For a subsonic round, 9mm will almost always carry more kinetic energy than a 5.56 projectile. Under Newtonian physics, the equation for kinetic energy is
E(k) = (mv^2)/2
where m = mass, v = velocity. At standard temp, pressure, and elevation, an object can move no faster than 1125 ft/s before it creates a sonic boom, but the exact speed we decide on here is really irrelevant, because in the experiment and the equation, it is a constant when considering both rounds. On any given day, fired under the same conditions, both a 9mm projectile and a .223 projectile will have to reach the same minimum speed in order to create a sonic boom, which for the sake of the experiment, is something we wish to avoid.
popular subsonic 9mm ammo seems to be at weights of 147gr and 158gr. Most of the weights I am seeing for subsonic 5.56 seem to float around 100gr.
Could a person theoretically manufacture a much lighter subsonic 9mm cartridge or a much heavier sub sonic 5.56 cartridge? Absolutely, but what's the point? When you have an upper boundary you must stay under such as the sound barrier, the only other option that exists for moving more energy with a projectile is increasing the mass of the projectile itself.
If you were running a can, would you not need to be using subsonic ammo to be effective?
Either way it supresses. I'm sure it is far from quiet using standard ammo. I'll leave someone that has one to more fully answer that. I know at least a couple of people on here have them. I think I read a thread on it in the NFA section.
OK here we go...
Being loud isn't always a negative, in fact its the main reason I built mine. Pure, unadulterated awesomeness.
None. 10.5" is typically the shortest you'd want to go on a true battle rifle. I've heard of quite a few SWAT guys running 7.5", but they're only shooting across rooms, so they're not as hindered by the short barrel as an Army Ranger would be.
Your logic seems absurd to me. Have you priced MP5's lately? Nobody runs a can on a 7.5" barrel, the massive pressure coming out the barrel can damage the baffles.
When I put my can on my 16" AR, its as quiet as a .22. I've never ran subsonic through it.
Supersonic suppressed 5.56 is amazingly quiet. So you get a sonic crack....who cares? It pretty much sounds like unsuppressed .22LR. Much better than touching off an unsuppressed 5.56 indoors with no ears on.
I don't know of any suppressor manufacturer that will warrant their cans on barrels under 10". Even if the can works fine on the 7.5", it's life will be reduced considerably.
I could post some new pics of my NT4 since I took those. That can now has about 3,000 rounds on my ten inch gun, and about 1,000 through my 14.5 gun, and I can't say that I notice any change in sound. The blast baffle still looks like the surface of the moon, but it's still a Knight's can, not to mention The 5.56 caliber rifle Silencer, so it's blast baffle is thicker than probably all others on the market. Plus, it's all inconel, so while it weighs a ton, if I haven't broken it by now, it's probably good to go for a while. I have had it glowing red, quenched it in cold water, and done it again. It's still my favorite AR silencer. I will say that the finish looks a lot nastier, but I'm still impressed that it has put up with temps that set a picnic table on fire.
Rob
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