Where are your optics zeroed in terms of total elevation travel and are you using a canted mount on an AR15/AR308?
A few months back I sent a Leupold Mark 4 3.5-10x40mm M1 FFP scope to Leupold to have the vastly superior M5 adjustments installed. Once I got it back I mounted the scope on a POF P308 rifle using Nightforce Ti rings that came with a Nightforce scope I bought in 2013. The center of the scope sits 2-7/8" above the center of the bore. It was easy to zero the scope and all was good. Earlier in the week I ordered/received a Vortex Viper PST 4-16x50mm FFP scope with the idea that I would use it on the POF and move the Leupold to another rifle. Before removing the Leupold it occurred to me to see where the zero was in terms of total elevation travel. It turns out that a 100 yard zero only left me with 5.2 mils of vertical adjustment which means that I would run out of adjustment beyond 600 yards. That particular Mark 4 has 20 mils of total vertical adjustment so the zero is at 3/4 of the total travel i.e. only 1/4 of the total vertical range is useful. I have the new Vortex mounted but haven't zeroed the scope yet. I'm hoping that it zeros much closer to the center of the vertical adjustment range giving me something closer to 8 mils of vertical adjustment but somehow I think I'll be back where I was with the Leupold.
Most AR mounts that I've seen/used including LaRue and GG&G don't have any cant built in. Some companies do make canted one-piece mounts but most seem to be for bolt action rifles rather than AR15/AR308 rifles. Back to the original question ... where are your optics zeroed in terms of total elevation travel and are you using a canted mount? Here's the rifle with the Leupold scope. POFs forend and integral rail add about 1/2" to the top of the receiver, hence the medium rings which put the scope where it needs to be.
A few months back I sent a Leupold Mark 4 3.5-10x40mm M1 FFP scope to Leupold to have the vastly superior M5 adjustments installed. Once I got it back I mounted the scope on a POF P308 rifle using Nightforce Ti rings that came with a Nightforce scope I bought in 2013. The center of the scope sits 2-7/8" above the center of the bore. It was easy to zero the scope and all was good. Earlier in the week I ordered/received a Vortex Viper PST 4-16x50mm FFP scope with the idea that I would use it on the POF and move the Leupold to another rifle. Before removing the Leupold it occurred to me to see where the zero was in terms of total elevation travel. It turns out that a 100 yard zero only left me with 5.2 mils of vertical adjustment which means that I would run out of adjustment beyond 600 yards. That particular Mark 4 has 20 mils of total vertical adjustment so the zero is at 3/4 of the total travel i.e. only 1/4 of the total vertical range is useful. I have the new Vortex mounted but haven't zeroed the scope yet. I'm hoping that it zeros much closer to the center of the vertical adjustment range giving me something closer to 8 mils of vertical adjustment but somehow I think I'll be back where I was with the Leupold.
Most AR mounts that I've seen/used including LaRue and GG&G don't have any cant built in. Some companies do make canted one-piece mounts but most seem to be for bolt action rifles rather than AR15/AR308 rifles. Back to the original question ... where are your optics zeroed in terms of total elevation travel and are you using a canted mount? Here's the rifle with the Leupold scope. POFs forend and integral rail add about 1/2" to the top of the receiver, hence the medium rings which put the scope where it needs to be.
