Scope Height. Is higher better?

[Texas Sheepdawg]

This topic could easily apply to just about any firearm including the 450 Bushmaster, but right now, let's discuss my current build, the 6.5 Grendel. This is what I have so far. I assembled the upper just to make sure I had clearance between the scope and the hand gaurd. the clearance right now is approximately .300". The distance between the center of the bore from the crosshairs is approximately 3".
With a Grendel, is this plenty of height, or should I go higher?
As I previously pointed out, this is only a preliminary fitting and I know that I am going to have to install the barrel first before installing the hand guard and other goodies. I haven't tightened anything down. The Barrel has not arrived yet, but will be an AA 24" Stainless with a threaded muzzle.

grendel upper 100611.JPG (33.81 KiB) Viewed 15452 times

[Hoot]

Everyone has a personal opinion on this and here's mine.

The closer the scope is to the barrel, the better.

Limiting factor(s):
My experience with ARs has been that unfortunately, when the scope is as close to the barrel as possible, it is not high enough to see through with proper cheek weld. It amazes me to see folks at the range shooting through a scope with their head bobbing above the stock. Anyway, whenever possible, I mount the scope as low as I can and still see through it with my cheek welded to the top of the stock and feeling as ergonomically comfortable as possible. If the stock has an adjustable comb, all the better, as you can set it to agree with your body's dimensions within it's range of adjustability.

Don't set the comb to agree with the scope. Set it with your eyes closed and settled down into it to where it feels the most natural. Lock it there and then adjust the scope through different height rings to work with that comb setup.

That's my humble opinion.

Hoot

[Texas Sheepdawg]

Stock will be Gunnys' A2.

[Hoot]

Stock will be Gunnys' A2.

Where does that scope in the image above line up for you when you have the gun mounted? If it matches you eyes, leave it there. Though it's not like you can do much if it doesn't. That's why I don't like one piece solutions like the PEPR. I use a set of YHM risers and a set of rings on top of them. If the scope is the wrong height, I can use a different set of rings. Some brands of rings have an XX-High model for ARs that eliminates the need for risers. I have never tried them as I'd rather use regular rings and a set of risers for the reason already mentioned. I'm at work, but IIRC, using the YHMs, it takes a set of high height rings to line my scope up with my eyes. Folks who have a tighter cheek weld or different head geometry may get by with a medium high set.

Hoot

[BD1]

It is my understanding that the original M-16 configuration was designed with no drop in the stock to allow proper eye position using the rear aperture sight mounted in the carry handle @ 2.5" above the line of the bore. For most folks keeping that sight height allows the A-2 stock to properly align your eye with your optic in most situations. Average height, average mount, average eye. I think that is the reasoning behind the one piece mounts maintaining that 2.5" above the bore. The trouble starts when you get into magnifications over 7x or 9x, and your pupil alignment becomes more critical, then you may need to adjust either the mount height or the comb height to insure that you don't have to hunt for the ocular image when you shoulder the rifle. It will also make a difference whether you're setting up primarily to shoot from a rest, off hand, or slung up tight, as your head position will vary with shooting position. I've hunted with more than one guy who was an ace off the bench, but then couldn't find the deer in his scope in time to make a shot in real time. Unfortunately there's no real way to set this up in advance of putting the whole works together.

My "varmint rig" is my old high power rifle, and it's set up so I can use the same head position I used to shoot high power with my cheek tight and my nose right on the charging handle. If I tried that with my .450B I'd have a permanent blood streak down the right side of my face, so that rifle has a recoil pad which puts my face back an inch and brings my nose up a hair. To compensate I glued a piece of 1/4" neoprene on the comb where my cheek rides which restores a good cheek weld with my eye right back on the ocular image. You just need play around with it a bit until you get it right.
BD

[Hoot]

If like me, you use a slip on Limbsaver recoil pad, that changes the LOP and does get your head a little further back. As in not needing to use a mount that has a forward rake like the PEPR. In my case, with my particular geometry, my nose is nowhere near the charging handle and it likes it that way.

YMMV.

Hoot

[bushmeister]

I'm with Hoot, closer is better. Much less math required for close shots.

[BillytheKid]

This is an over simplification, since projectiles travel in arcs and not perfectly straight lines, but, here we go:

If you mounted a "scope" laser to be level in your scope rings, and inserted a "bullet" laser bore sight level into your barrel, you would see two parallel laser beams that do not meet on a target at any distance.

The way to make the "scope" laser meet the same spot as your "bullet" laser is to angle your "scope" laser down a bit.

But, your meeting of the lasers will only occur at a specific distance, after which, the "scope" laser will descend below your barrel laser.

The higher your "scope" laser is away from your "bullet" laser to start with, the farther apart they are for most of beam length.

The closer your "scope" laser is to your "bullet" laser to start with, the closer they are over a longer distance of beam length.

[MOUNTIN DU]

...not to mention that canting in either direction amplifies your windage error as well
nice analogies... if more people understood how important cheek weld is when related to recoil there'd be fewer scope eyes as well
for me, length of pull & eye relief; with winter hunting clothes on, and scope height make proper cheek weld possible. jm2c

[Texas Sheepdawg]

I am very comfortable with the PEPR and this scope. I guess what I am really looking for is, not so much fit, rather if there are ballistic advantages using the .264 bullet with the Grendel ballistics with a scope mount higher than what the PEPR already offers. Would higher positioning give me more or less range or is what I've already got perfect for the cartridge? To be honest, I really like where it is right now, but if a half inch higher would give me a couple hundred more yards, I'm game. HOWEVER, if the PEPRs height is good enough out to 400 yards, I shouldn't even need to wory about it?