TargetTalk

Hey guys, I need some help. I just bought a new Bushnell Banner 6x-18x 50mm scope for my .177 co2 pellet gun I use for target practice. I tried to get ruff centering before my official longer range zero in and I ran into a problem. It will shoot in the centre of the cross hairs at 8 yards but only with FULL elevation dialed. This leaves me with no leeway elevation for longer distances past the second point of intersection with the scope cross hair which isn't too far.
I don't get it.
Am I missing something? Do I need a new scope?

You need to add a shim to the bottom of the rear scope mount.
Use something thin and flexible that's not easily compressed.
A lot of people use thin strips of photographic negative. You will probably only need one or two small pieces, cut so that they are no more than 1/4 of the circumference of the scope body, and laid in the lower mount. Don't glue or tape them in place, just trap them between the mount and scope body.

Ideally, you want to have the whole setup adjusted so that the scope's adjustment is centred in its movement at the range you usually shoot at.

An alternative to shimming (although more $$$$) would be to use Burris Signature rings. These rings have replaceable inserts that allow you to add or subtract elevation as needed - a very handy design. And, they're available in the typical rimfire 3/8" - 11mm rail size. Here's an example - http://www.midwayusa.com/viewProduct/de ... ber=430969

Hope this helps.

Mike

I'm going to try the shim idea, I'm glad I don't have to buy new rings.

I shimmed under the scope in between the back ring with 7 layers of photo film negative and it worked perfectly. Now my scope has 78% elevation to spare. :) Thanks!

at 8 yds, it's probably the fullest elevation you will need, so in that respect, your longer ranges will be ok.

if you are running around 800 fps with .177 you will be dialing up most at 8, least 25-30yds, and somewhere in between for 55yds.

I am running at 5.5 MOA for 55yds, 0 (obviously) for 25-30 and 9 MOA for 8 yds, with 10yds needing 6.5 MOA

Depending on how many MOA you have in a turn on your scope, that range should be covered by about a turn. However it is good practice, if you're dialing a lot to try and keep away from the extremes of the dialing range as you can lock turrets up if you are hamfisted.

It will need more if you run a slower speed, and the flat spot will move further in. It will move further out with higher mounts, and faster speed.

I prefer to use adjustables, as shimming stresses the scope tubes, which can manifest itself in all sorts of ways. Sportsmatch do an excellent range, as do B-square, but the B-squares are a faff to setup, and the elevation only adjustables from sportsmatch take barely more than a few secs in addition to a normal zero. It also allows me to keep optical zero at my prefered range where i need the scope to work at it's best.

Lap the rings first. Zero the scope to it's optical center. Your best scope picture is midway between the bottom and top and also side to side. You will not pick any of the aspherical aberrations and other abnormalities when you are looking through the center of the scope. Wax the bottom of the scope. Apply bedding compound to the bottom rings. Lock your gun in a bench vice.Pull the bolt. Place a target at the distance you prefer to shoot. Look through the barrel and center the target. If it is long distance, figure the drop and place a second target above the first so as to equal the amount of drop. Screw the top rings on so that the crosshairs and the barrel intersect at the target. Let it cure. Hope this helps.
Chris

or buy adjustable mounts and remove the need for lapping ;_)