Question regarding Picatinny rail install

P

piniongear

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Can someone tell me what the difference in bullet impact point is at 100 yds when using a Nightforce 20 MOA rail compared to a 40 MOA rail on a Remington 700?
Thanks......pg
 
1 MOA is approximately equal to 1" at 100. 2" at 200, and 10" at 1,000 yd., so you are looking at a difference of 200" at 1,000 yd. Yes?
 
Let me state my problem.......

My problem is as follows:
I bought a Nightforce 12-42X BR scope.
I bought Nightforce high rings.
Tried to put this on a Sako 6PPC with a heavy Hart barrel and the scope hits the barrel.

I sent the high rings back to exchange for extra high rings.
That worked fine on the Sako after that.

I then bought two Nightforce Picatilly rails for a Remington 700. Both rails are 20MOA.
I installed one rail on a Rem 700 204 Ruger and the other rail on a Remington 221 Fireball.
I bore sight the 204 and take it to the range. No problem. I have no problems with running out of adjustment and that is what I expected.

Now comes the problem:
I moved the scope and rings over to the Remington 700 221 and cannot get it bore sighted. I run out of elevation on the scope. With the elevation knob cranked all the way down, the center of the bore sight is still way below the cross hairs.

I take it to the range anyway and cannot even get the shots on paper. I aimed as much as a 18" high and low but no holes at 100 yards. I walked down to the pistol range and with the bolt removed I looked down the barrel and then the scope. No adjustment available.

I go home and move the rail, scope and rings to a Remington 700 308.
Same result with the bore sight. The cross hairs will not reach the bore sight center by the same amount as before. So I decide it is no use taking it to the range.

Now every one of the rifles mentioned have always shot well using Leupold scopes and no problems with running out of adjustment. The Rem 700 204 shoots well with the new scope.

I had a similar problem recently with installing a Burris Black Diamond scope on a Winchester 22-250.
I ran out of adjustment on the elevation. So I decided it must be the scope, although it worked well on the rifle that the Burris was on before.

I sent it to Burris and they returned it saying there was nothing wrong with the scope.
They said check my mounting.

What is there to check?!!! The rails go down tight and so do the rings.
There must be something I am missing here but I have no idea what it could be.
Any help is certainly welcome.
Sorry for the long tale, but I just wanted to list what I have done and the history of the problem.
Perry
 
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Remount the scope to the rifle using a rail with zero cant. Sight in rifle at 100 yards and see how much verticle adjustment you have left. IF you need more travel to reach the range you want to shoot THEN you can decide how much cant you need in the rail.

For example, I've had a Sightron 36X on my F-Class rifle. With it's limited verticle travel I need a canted rail to have enough travel to reach 1000 yards. Truoble is there isn't a wide selection of rails available for a Winchester short action. A 20MOA rail gets me to 1000, the issue is the rifle prints 6" high at 100 yards with the scope adjustment at the bottom of the range. It's still over 3" high at 300 yards which doesn't work for me because we shoot matches from 300 yards out to 1000 yards.

Probably nothing wrong with your scope, the height difference between the front bridge and the rear bridge on your actions aren't the same.
 
Thanks for your reply Al, but I remain completely confused.
As far as I know I can get either 20MOA rails or 40MOA rails for the Remington, not a zero cant. I chose 20MOA.
For the Winchester all that is offered is 20MOA.

So this rail slopes down towards the barrel, correct?
That makes me visualize the scope pointing downward also which means to shoot higher I would raise the end of the barrel by elevating the cross hairs up.
I only shoot at 100 yards.

The guns are all Remington 700 rifles, just different calibers.
The scope works fine on the 204 but does not work on the 221 or the 308.
I cannot see how the top surfaces of these recievers could vary.
When Nightforce says a rail is for a Remington 700 I guess I expect it to fit and work perfectly.
And it does on the 204, but not on either of the other 700 rifles.
I continue to be missing something here.
Perry
 
Perry, factory actions and barrels are not straight, some are not even close. Aftermarket rails usually are. Ken Farrell makes good rails and they come in zero moa for your rem 700. By the sounds of it you need more than 20 minutes to zero at 100. If so, the barrel is likely the worst part of the problem. Burris makes rings with inserts, they should work well for a 221 or 308.
 
"Usually" and "most of the time" a 20 minute mount on a Remington 700 will be just right and what you would expect as normal and will not be an advantage in long range shooting. Yes the top surfaces vary a lot.

When you install the rail tighten the front mounting screws first. I'll make a bet that there will be space under the rear mounting area. A simple shim will work and give you a true 20 minute of look down. Sinclar's sells the shims.
 
Well, I may have to try the shims.
But what puzzles the heck out of me is installing the rail on the 700 204 worked perfect.
Not so on the 221 or the 308.
The rails are all Nightforce 20MOA for a Rem 700, so I consider those rails quality to be top notch.
Also, all the rails fit tightly against the receivers on all three rifles.
I do have a NF Winchester 20MOA rail headed my way this week.
This will go on a Model 70 Varmint and I am very curious to see if it also gives me the same problem.

Do the size of the scope rings have anything to do with the setup, other than give clearance with the barrel and scope lens?
The Rem 204 has a heavy barrel and 1/8 inch clearance between the barrel and lens.
The 221 and 308 each have standard barrels and have a half inch clearance.
pg
 
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