Originally Posted by ChattanoogaPhil
Using .22LR High Velocity ammo in 4.5in barrel will result in a velocity that's close to Standard Velocity ammo in a typical 16in barrel. About 1050fps +/-.
100yds no problemo. Example: With sight over bore of 2.5in and 50yd zero, will be about 7in low at 100yds. Adjust optic accordingly.
Not with an AR platform, but I shoot .22LR SV at 300yds. As mentioned above, the limiting factor is mounting and sighting system, not barrel length.
To add to this info I shoot a standard barrel 15-22 .22lr long range fairly accurately say under a half dollar at 100 yards.
I zero at 50 yards with a 3-9x40 Berska CQB scope with no riser and im one mil dot under at 75 and two at 100. This is important because as the poster I quoted mentioned thu bullet drop is 7 inches at 100 yards well each mil dot is 3.6" at 100 yards so a 7" drop is almost two full mil dots or atleastclose enough where the .2 of an inch wont matter as much as your shooting skills will.
A 50 yard zero makes 25 yards one dot over, 50 yards is on the cross hares, 75 yards is one dot under the cross hares and 100 yards is two dots under the cross hares. Out past this my groupings fall apart too much to deliver an accurate shot on an animal so I dont shoot past this with a .22lr. Not to say you cant.
However since your asking about an SBR AR-15 Conversion a lot of this is going to be dependent on the quality of the ammo, the conversion and how it all works with the barrel you have. The length of the barrel is going to hurt accuracy as will the difference in twist rate also I believe a .223 or 5.56 barrel does have a slightly larger bore then the .22lr add to that the velocity difference and you can see why its possible but probably wont be a tack driver.