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TrueBlue711
June 28, 2017, 09:46 AM
My SCAR 17 has the GG&G QD scope mount, but it puts the scope about 3.5" over the barrel. I'm debating about looking for a new scope mount that mounts the scope closer to the barrel. What are the advantages/disadvantages of having a scope higher above the barrel vs hugging the barrel as much as possible? I'm sure it's different for different calibers (flatter shooting bullets for example), but I'm wondering specifically for the .308.

EDIT: I think I just answered my own question. Played with a ballistic calculator and plugged in different scope heights. It seems the lower scope heights will have less variance between you and your zero, but drops faster after the zero than the higher scope heights. So if you're looking for less drop from zero at longer distance, stick with a higher scope height. That sound right?

emcon5
June 28, 2017, 11:02 AM
Pretty much. Generally speaking, a lower scope will give you the perception of less drop before your zero range, and higher scope will give you less perceived drop beyond your zero range.

If past experience is any indication (https://thefiringline.com/forums/showthread.php?t=400143) then stating that rather simple concept will bring out folks who have never heard of it, refuse to believe it, won't bother to run the numbers, and strongly proclaim that as low is possible is the ONLY way to go, and if you think otherwise you are a moron.

If your stock gives you a good cheek weld with the scope that high, then I wouldn't mess with it.

Art Eatman
June 28, 2017, 11:10 AM
If you know the trajectory of your load, what does the height matter, once you've sighted in?

E.g., my '06 with a 200-yard zero drops about two feet at 400 yards. So, I hold two feet above the desired point of impact. What matters is what you see for an "air gap" between the cross hairs and the desired POI.

FrankenMauser
June 28, 2017, 12:31 PM
Is it even possible to go much lower without cutting the stock off the rifle?

The SCARs look, to me, like you're almost universally stuck with a high scope, since the mounting rail and stock are so high in relation to the barrel.
Even if you want a scope mounted really low, it becomes nearly impossible to actually get your eye low enough to use the scope.

TrueBlue711
June 28, 2017, 12:58 PM
If you know the trajectory of your load, what does the height matter, once you've sighted in?

You're right, with trajectory knowledge, it really doesn't matter. Just a thought that crossed my mind.


The SCARs look, to me, like you're almost universally stuck with a high scope, since the mounting rail and stock are so high in relation to the barrel.

Absolutely true. Even with the lowest scope rings possible, I think it would put the scope at 2.5" or somewhere around that above the barrel. Definitely won't get the same "closeness" a bolt gun would get with it's scope.

emcon5
June 28, 2017, 01:28 PM
If you know the trajectory of your load, what does the height matter, once you've sighted in?

For known distance target shooting, no real difference. For hunting it can give you a little more margin for error if you estimate the range wrong. Depending on the load, you will get a little longer MPBR with a higher scope. Not a huge difference, but it is there.

With a .150gr .308 @ 2800 fps between with 1.5" and 3.5" sight heights, your MPBR is 329 and 345 yards respectively.

For a 200 yard zero, your drop at 250 and 300 yards is 3.3" and 8.4" for a 1.5" sight height, and 2.8" and 7.4" for 3.5".

Again, not a huge improvement, but it is there.

On edit: Much more important is getting a good cheek weld, which is really the determining factor in scope height. If the stock is adjustable, you have some options, if not, you are kind of stuck with what the stock allows.

JoeSixpack
June 28, 2017, 01:32 PM
depends on what you're using, scopes for distance less of an issue, if it's something like a red dot you'll have to compensate at close range for the offset.

I don't do much shooting beyond 200 yards so I prefer low mounts.

cw308
June 28, 2017, 04:11 PM
Scope height should be as low as possible without touching the barrel , cheekweld is important for accuracy.

TrueBlue711
June 28, 2017, 04:24 PM
cheekweld is important for accuracy
Agreed, but the SCAR stock has adjustable cheek riser. I have a good cheekweld even when the scope is 3.5" above the barrel

std7mag
June 28, 2017, 06:48 PM
Just be aware, Strelok determines scope height from the objective lens, not the middle of the scope...

Just found this out the other week... :rolleyes:

jmr40
June 29, 2017, 05:59 AM
If you know the trajectory of your load, what does the height matter, once you've sighted in?

At closer ranges (under 200 yards) a scope mounted high can result in the bullet being WAY above point of aim. Enough to easily miss high on shots unless you remember to hold low. This is certainly possible, but not natural. Everyone naturally will hold high on long shots, but will often never think to hold low on close range shots..

Scopes on hunting rifles are generally 1-1.5" above the bore. With a 100 yard zero most bullets will not be more than 1/2" high or low from 50 yards to nearly 150 yards. You don't have start worrying about bullet drop until 200 yards and NEVER have to think about holding low.

With a scope mounted extremely high and a 100 yard zero you'll be 2-3" low at 50 yards and could be 5-6" high at 200 yards with the bullet coming back to zero again around 300 yards. If you only plan on shooting 300+ yards having a scope mounted very high is actually an advantage. But it just complicates matters at common ranges.

Mobuck
June 29, 2017, 09:20 AM
"Scope height should be as low as possible without touching the barrel , cheekweld is important for accuracy."

Sort of. Scope height should be determined by how you "cheek the stock". When the rifle is mounted, your eye should align with the center of the scope's lens plane w/o head bobbing or searching. My pet peeve is watching hunters "hunt and peck" for their crosshairs while the game walks away unscathed.
We went through a rather frustrating session with Grandson last year. He complained that he couldn't see the cross hairs and/or his shots hit in a here and there random pattern. I finally determined that his eye wasn't lining up with the center of the scope. We fixed that and his shooting and attitude improved.

cw308
June 29, 2017, 11:02 AM
TrueBlue711
Sorry I'm a built action guy , as long as your cheek riser puts you in line with your scope & shoulder position that's fine. Why was it set up with high rings ? Flat top AR's scopes are set up pretty low. Bolt actions bolt lift could be a problem in getting the scope low , stock shape for cheekweld. I shoot a Rem. 700 308 cal with a HS Percision stock, still had to install a cheekweld. Every hold position should be the same with every shot. My scope is 1/4" above the barrel.