OBR and S&B scope zeroing question

[DeltaOneSix]

Running a Larue OBR 308 18" with a S&B 5-25x56 PMII MTC LT H59 CCW. Now the OBR has a 20 MOA cant built in, plus the scope is mounted in the Larue 34mm OBR LT111 mount. So initial read when zeroing at 100 yards was that the rounds were hitting high. So the question comes in that by the time I have brought the scope cross hairs up to where the round is impacting to get POA/POI I have churned through one full turn of elevation adjustment on this double turn scope. Cap on top of elevation turret has popped up and shows black. Seems I am zeroed right in the middle of the scopes full elevation range.

Anyone else have a similar experience? Is this normal.

Thanks.

 

[HogBoss]

I've got the same rifle / same configuration on order and have almost the exact same scope (only difference... I've got DT dials). I'll let you know once I get my rifle.

For now, I've been running my PM II on a 20MOA base on my Remington 700 .30-06 (~22" bbl). I also have the LT 111 mount like yours. I zeroed at 100 yards and had about ~20 clicks till I bottomed out, I believe. I can verify later tonight. My loads are 168gr A-Max chron'ed at 2750 fps. That may be a bit fast compared to .308 loads of the same weight.

 

[Lowlight]

The scopes are designed to use 45MOA base to get a 100 yard zero and full elevation.

With a 20MOA base you should have more than enough, but will still be 25MOA short of reaching it's full potential

Once zeroed, you have to loosen the turret screws, then spin the cap free backwards to rotate the second turn indicator down. Once it is down you can then set the cap to 0 and move on... you'll more than likely still have 2 turns on the cap, and more than enough elevation for an OBR but it's not optimal in terms of the design. but it will work 100% for you.

Where it is in the adjustments range really doesn't matter, where you end up after zeroing does. I bet you have to close to 20MILS of adjustment. Just not the 26.

 

[RonboF117]

I believe I have the data you are looking for. I will get them out of my data book tomorrow and post them here for you.


Sent from my iPad using Tapatalk HD

 

[RonboF117]

Sorry it took so long to get you your reply but life got in the way. The following is the data I have compiled. Using an 18" OBR-7.62 w/ S&B PSR optic (same as yours), shooting SW Ammo 175g. Average muzzle velocity over two separate trials using a magnetopspeed chrono was 2540-2550 fps.

1. In a Spurh 0 MOA mount, 100 yd zero was 6.8 mils up from factory zero. Conditions 3870' density altitude, temp 83F, sta press 28.13

2. Using Bobro 20 MOA mount, 100 yd zero was .7 mils up from factory zero. Conditions 4250' density altitude, temp 87F, sta press 28.17

Hope this helps.