Doc, have you chronographed AR pistols or SBR's at shorter barrel lengths? I have heard there is a dramatic reduction in velocities.
Thanks,
Cody
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Shooting a firearm in a confined space will assault the ears, whether it's a handgun, shotgun or rifle. But if I ever find myself in a life or death struggle inside my home, I figure I'll be too involved with keeping me and mine alive to worry about hearing damage. Death or deaf, I know what my choice will be. But that doesn't mean protecting our hearing should be ignored. I feel a 11.5 inch AR in 5.56 with a short suppressor is one of the best choices for house defense. Minimal wall penetration, good terminal ballistics, low recoil, handy length, easy to use & shoot accurately and while the report is still loud, it's not nearly as unpleasant as shooting unsuppressed.
Hearing damage is cumulative. I don't know where on the spectrum a couple rounds from a rifle or shotgun compares to a 8-10 pistol rounds, but I bet it's close to even.
Personally I feel that the platform that will end the fight in the least number of rounds fired is your best choice, and given the options I would take the 10.5" AR.
txdpd--when tested in aggregate, 10.5" 5.56 mm AR15's are substantially less reliable than those with barrels in the 11.5"-12.5" range.
cclaxton--yes, we have extensively tested 10.5" Mk18's, 11.5" Colt Commando's, and 12.5" configurations.
Outside the box option: Styer AUG and a can?
Found this great table showing velocity results of various length AR barrels. They made a long barrel, ran a bunch of different brands of ammo through it and put the results in this chart. Based on this I estimate my 10.5in muzzle velocity with HQ ammo would be about 2500FPS,more than enough to yaw and break.
The quote from this article stood out to me: "Every bullet has a minimum velocity at which it will expand. In the case of most bullets for the AR, the method of terminal effectiveness isn’t expansion but yaw and breakup. For instance, the typical 55 grain FMJ, used in bazillions of .223/5.56 rounds, needs to be going faster than 2,300 fps in order for it to yaw and break. Slower than that, and it is basically a high-speed knitting needle. If your barrel is so short that you can’t generate that kind of speed, even at the muzzle, you are not shooting a .223 anymore."
Read more: http://www.gunsandammo.com/gunsmithi...#ixzz5BQGLE7tI
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@cclaxton
Checkout this thread on ar15.com; Suppressed 5.56 SBR Velocity Tests--41 Factory Loads from 10.5", 11.5", 12.5" & 14.5"