20 MOA Base and Zero


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fractal7
March 9, 2011, 01:37 AM
So I finally got around to getting a Leupold Mark 4 6.5-20 scope for my Remington 700. Since I am planning to try out some 1000 yard shoots, I got a 20 MOA 1-piece canted base.

I took it out to shoot the other day and the scope has roughly 70-75 MOA of elevation travel, so with the base I figured I would be cranking it way down to get sighted in at 100/200, however at 100 yards I'm almost dead center on the adjustments, and have about 42 minutes of elevation adjustment. Now I did a ballistic calculation and I need about 38 MOA to adjust out to 1000, so I have enough but just barely.

So my overall question is has anyone else experienced this with their setup? I figured with 70 MOA of travel and a 20 MOA base I would have been closer to having problems getting on paper at 100 than having just enough to make it out to 1000.

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ghostwriter
March 9, 2011, 05:36 AM
My first question is: Are you sure it's a 20 MOA ramp?
I have a 20 MOA ramp on my Savage 110 BA (300 win mag) and the Nightforce scope is turned almost completely down at my 100 yard zero, like only 1/2 to 3/4 MOA left to go lower. The rest is ALL up. In theory I have about 95 MOA available in the up direction so I'd check that first. Sounds like something isn't quite right.
You didn't say what caliber you were reaching out to the grand with but I assume it's fairly large.
With a 168gr VLD and 65gr of H4350 powder I need roughly 25 MOA to get on the paper. The drop is around 255". I also assume you've run the ballistics calculator on your load and chronographed it to get the correct velocity for the round you're throwing downrange.
Just a few things on my mind as you can see.

USSR
March 9, 2011, 08:11 AM
fractal7,

You're not really that far off. If your scope has 70MOA of total elevation travel, AND (big "and" that seldom happens) you end up in the middle of the elevation travel when you sight in at 100 yards with a non-sloped base, that leaves you with 35MOA of "UP" available. Now, since you have a 20MOA base, you subtract the 20MOA from the 35MOA, giving you 15MOA and leaving you with 55MOA in a "perfect world" where your reticle is centered at 100 yards. So, instead of 55MOA, you have 42MOA. That's plenty with the .30-06, and if you need 38MOA to reach 100 yards, you are definately using the wrong load. I shot mine at 1,000 yards for 3 years, and only needed about 30.5MOA to reach 1k. Oh, and BTW, I used the very same 6.5-20 Leupold scope.

Don

fractal7
March 9, 2011, 09:32 AM
I just think its odd that even with a 20 minute base, I have around 33 minutes of downward travel still at 100 yards, almost dead even in the scope's adjustments. It seems there is a lot of wasted clicks in there. Its a base from Badger Ordnance and did just double check to make sure the package said 20 MOA which it does, and it looks canted, perhaps I need to measure it somehow.

Also I'm shooting .308, with 175 grain SMKs. I chrono'd one coming out at 2633 fps but I think I still have some room to push them a bit harder with my load.

USSR
March 9, 2011, 11:19 AM
...I'm shooting .308, with 175 grain SMKs. I chrono'd one coming out at 2633 fps but I think I still have some room to push them a bit harder with my load.

Yep, 2633fps is JUST making it viable at 1k. If you've got a 24"-26" barrel, you should be up to 2700+ fps. USGI LC M118 LR with the 175SMK runs at 2718fps out of my 26" barreled FN SPR.

Don

Haxby
March 9, 2011, 01:33 PM
What rings are you using?
New gun, or has it been sighted in before?
Measuring the base sounds like a good idea.

fractal7
March 9, 2011, 01:48 PM
So its a Remington 700 5r, with Badger Rings and base. The base appears canted, I can't quite figure out how to measure it without unmounting the scope however.

It is a new gun, and I am just starting to get it sighted in/broken in (I have a total of 11 rounds through it). For my first shot at 25 yards I cranked my elevation down 20 minutes, expecting my shot to be high because of the base but I hit almost exactly 5 inches low and had to undo it.

ghostwriter
March 9, 2011, 02:38 PM
here's a stupid question... was it put on correctly? low side to the front... LoL. Wouldn't be the first time someone did that. It happens. Looks like you need a pair of calipers to get the numbers from each end and compare. Thin side forward... and it ain't much different.
I realize you just got the scope mounted but trying to fix the problem without confirming these basic things will be just throwing good ammo after bad. Double check and confirm. I bet you find the issues and I bet you slap yourself in the firehead and say, "dooh!!"

When I sighted mine in the first time, I took out the bolt, put the target out there at 20-30 yards and looked thru the bore to the target center adjusting the rifle slightly to see the target centered in the bore. Then, without touching anything I looked in the scope and gently adjusted the crosshairs to the center of the target as well... double check again a couple of times just in case something got bumped and then shoot. The result for me was my first shot was high and to the left about 2-3 inches! Maybe I just got lucky. This was first shots at a 100 yards too.

fractal7
March 9, 2011, 03:06 PM
here's a stupid question... was it put on correctly? low side to the front...

Thats one of the first things I checked. It sighted in just fine, I put up a 0.5" 3 shot group at 100 yards, its just I expected with the canted base I would have more runout on my elevation adjustments than I do and I was wondering if anyone else had a similar situation with their setup.

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