Scope Height in Relation to Usage?

[lizard]

Every time I'm trying to match a scope to a rifle seems I always have to wrestle with scope height from barrel. Or more clearly distance between center of bore and center of scope. Can't seem to start off with the rite height of rings. My biggest worry is if the scope sits too high does it effect the accuracy. When I try to think it out seems like you are just changeing the point of impact past your zeroed distance. Of coarse holding the rifle and scope in near perfect verticle position would come into play to as the scope height gets higher.

I have such a issue currently and would like to have your advise or input. I have a same as brand new Savage 12-BVSS in 243 caliber. Just mounted a Night Force 12-42X56 Benchrest scope. Under advise from the scope manufacture I should use the NF 1.125 rings and NF 20 moa one piece base for my application. I did and after mounting the components I have a full 3/8" space between bottom of scope and top of barrel. This translates to aroud 2 and 1/4", (I think), (I have already disasembled it) between center of bore and center of scope. My question is is this measurement of any revelance to support accuracy or usage of the rifle in any way. I intend to zero at 200 yds. and probably not shoot out past 300 yds. very often. Am I worrying about something that really don't matter?

Looks like I have a couple of options if I choose to lower the scope. A 1.00" set of NF rings that would bring it down 1/8" or a .885 set of NF rings that will bring it down almost 1/4". The .885 seems like the rite ticket if lowering it is of any bennifit other than looks.

I'm open to comments, Thanks, Mike

[scope eye]

You always want the scope as low as possible, no exceptions.

Tanks Dean

[rgburrill]

For maximum point blank range you actually want the scope high, not low, especially on a 243. Using the Winchester Ballistics calculator, for a 95 gr Silvertip and a 200 yard zero crossing with a 1.5 inch high scope the bullet drops to -6.4 inches at 300 yards. With a 3 inch high scope it drops to only -5.6 inches. Furthermore, by properly adjusting zero crossing, a 1.5 inch high scope height only gives you around 290 yards MPBR while 3 inch gives you around 320 yards.

[pitsnipe]

For maximum point blank range you actually want the scope high, not low, especially on a 243. Using the Winchester Ballistics calculator, for a 95 gr Silvertip and a 200 yard zero crossing with a 1.5 inch high scope the bullet drops to -6.4 inches at 300 yards. With a 3 inch high scope it drops to only -5.6 inches. Furthermore, by properly adjusting zero crossing, a 1.5 inch high scope height only gives you around 290 yards MPBR while 3 inch gives you around 320 yards.

I would follow scope eye and put the scope as low as you can for NOT only asthetics but ALSO for the ability to get a 100 yard (if you wanted it) POA/POI. AND, to have all the scope can give you in "up" adjustment IN CASE you ever wish to stretch yours or your guns "legs" and go out to 600 and beyond. That said Im confused by rgburrill's answer. The drop of a bullet at distance is directly related to its ballistics. Not how high off the barrel the scope is sitting. I would get the same drop in inches of a bullet at 200 yards (with lets say a 100 yd zero i.e. POA/POI) If I used a scope to aim at that 200 yd target as much as I had used open sights. The cant error (as the OP pointed out) would be exponentially greater (all other factors i.e. wind, bullet BC, being equal) the higher the scope sits. This is basic geometry. Bottom line..... GO LOW
Good shootin!

[scope eye]

That's why there's that notch in the bell of the Leupold VX series.

Tanks Dean

[rgburrill]

I would follow scope eye and put the scope as low as you can for NOT only asthetics but ALSO for the ability to get a 100 yard (if you wanted it) POA/POI. AND, to have all the scope can give you in "up" adjustment IN CASE you ever wish to stretch yours or your guns "legs" and go out to 600 and beyond. That said Im confused by rgburrill's answer. The drop of a bullet at distance is directly related to its ballistics. Not how high off the barrel the scope is sitting. I would get the same drop in inches of a bullet at 200 yards (with lets say a 100 yd zero i.e. POA/POI) If I used a scope to aim at that 200 yd target as much as I had used open sights. The cant error (as the OP pointed out) would be exponentially greater (all other factors i.e. wind, bullet BC, being equal) the higher the scope sits. This is basic geometry. Bottom line..... GO LOW
Good shootin!

The drop I talk about is the drop below the aimpoint. When first fired the bullet obviously climbs above the aimpoint - how high it climbs is dependent on how high the sight is above the barrel. When you are shooting for MPBR you are concerned about how far you can shoot and stay within 3 inches above and below the zero line of sight to target. That gives maximum kill zone on medium game like deer without worrying about the true distance to the target.
If you don't believe my numbers run the calculator yourself. Just remember on the MPBR calculation to adjust the second zero crossing to give a miximum rise above zero of just under 3 inches.

[CJnWy]

Lowering the scope with the .885 rings will also help with cheek weld.

[lizard]

Thank all of you for your responces. Now I am really confused. Does the 20 MOA Nightforce base have anything to do with the different answers that we are getting. I am taking into account each and everyones point of view. I just have not got it sorted out exactly yet. I have emailed back to the tech support at Nightforce a few days ago but no responce yet. Was going to ask them if their reccomendations were based on the 20 MOA base, the NP-R2 reticle, heavy varmint barrel and or the caliber. On their previous advise I had specified all of the factors about the rifle and the 200 yd. zero range and possible 300 yd. occasional shots. Maybe because I sent a picture their system kicked the email out or something.

I have never used a 20 MOA base before and it actually cants the scope front end down making it look a bit odd to me. I'll probably get used to that soon and not notice it. I did order the .885 rings and when they arrive I will let you know how they work out.

Thanks again and keep the comments coming, I am learning from this, Mike

[rgburrill]

Yes it cants the front end down 20MOA - the same as canting the barrel up 20 MOA. At 200 yards thats about 40 inches which is way too much for 243. Again using the Winchester Ballistics calculator (super easy to use online) a typical 243 with a scope zeroed at 100 yards (0 MOA mount) will only drop less than 3 inches at 200 yards. With a 20 MOA mount you will have to RAISE your reticle almost 18.5 MOA to get a zero at 200 yards. To put it another way, assuming everything was dead on factory settings (zeroed at 100 yards with a 0 MOA base) when you first test it after mounting with that 20 MOA base you will be about 37 inches high at 200 yards. Without using a ballistics calculator you will scratch your head forever to figure out where your bullets are going. I love the 243 simplly because it fires such a low profile shot - just like a 270 without all the shoulder damage ;<)

FWIW, a 20 MOA base for a 243 would allow you to zero the scope at 500 yards.

[rgburrill]

BTW, you never said what you are using it for. If you are looking at shooting holes in paper at fixed distances and have a few minutes available to read a chart and adjust clicks then a low mounted scope "might" work best. OTOH if you are walking through the woods and need to bring down a deer at any range from 25 yards to 300 yards then the high mounted sight gives more maximum point blank range for the kill zone. One problem with a high mount, however, is calculating hold over or clicks - you really need a ballistics calcultor for that or a lot of shooting at the range. And for target type of shooting cheek weld is very important and that will depend on your face - that's why is said "might" above.

[CJnWy]

I just put a 20moa EGW base on the 7mag BVSS and an IOR 6-24x50 with a 35mm tube. Even with low rings the scope is dang near 1/2" off the barrel. Trying to site it in I had to dial all the way down and use the the 10moa hash mark above the x hairs to hit what I was aiming at. Well with wanting to be 10moa from the bottom and holding 10moa high a 0moa base would be just perfect=WRONG With the 0moa base I was just a couple moa from dead center WTF???
So I put the 20moa base back on and put a small wire under the front between the screws and snuged it back down a little,put the scope back on and WALLA It boresited 10moa from the bottom. Took everything back apart,sprayed the action with Pam and JB welded the base back on with the wire still in place.
I sure hope it works this time? I'll get out tomorrow to shot it again for effect to find out. The plan is to have a total of 65 moa of up so I can get to a mile with it???
The whole idea behind a 20moa base it to be able to set the scope 20moa lower than center so you end up with more room for adjustment up for longer range...To 300 yards it dont matter as long as it zeros