10 MOA vs 20 MOA

[keystone112]

Looking to put a one piece rail on a 308 bolt gun. I won’t shoot long range often, but I will occasionally say 600 yards or so. Leaning towards an SHV 4-14.

So what is the best option here? 10 MOA rail or 20 MOA.

 

[mrolen]

20 moa

 

[dieselchessy]

With a 168-ish and 100 yard zero 600 yards is around 17 moa. With that scope you should have 30 to 40 moa up travel off your zero. (90 moa advertised travel, zero just above center of travel)

20 moa gives more up travel but also a higher eyepiece position and lower objective position all things being equal.
10 moa gives a little more up travel, but less of a raised eye piece position.
If your going to be lobbing 175’s or bigger 20 moa rail might be it.
Even with lower BC hunting bullets you shouldnt have issue getting to 600 with no rail.

Everything is a compromise.

Check my math, my assessment is worth what you paid, but should show the thought exercise for you.

 

[Macintosh]

If that scope has 90moa of travel (I did not check, just going off above post), then that leaves 45moa of useable elevation. Call it 40 because your zero might not be perfectly centered.

So if your dope for 600 yards is 15moa you have plenty of travel with no rail. At 700 you are only using HALF of the available travel without any rail at all at about 20moa required, and your 850 yard dope is roughly 30moa (just guesstimating off my 3006)…then with NO rail it’ll be possible to dial that scope PAST 850 yards, although you may be near the extreme amount of travel for the scope. That means the springs in the erector are compressed all the way, and the “common wisdom” (for what thats worth”, maybe not much) is that the extreme ends of erector travel are where youd have any issue.

A 10moa rail would give you an additional 10moa of travel, so 50-ish total (zero would be -10 from where it is without, so you have 10moa to center, plus the full travel from center to top). You arently likely to need the additional travel, so the only benefit would be keeping the portion of the erector travel you use closer to the center of its useful range. In that case you’d never be more than 10moa from the center of elevation travel out to about 700 yards, and you’d only be using about half the up-travel to get to 850 or so.

Based on the above I see no reason to go with more than a 10moa rail unless you will be shooting a bunch PAST 850-ish yards. And if you wanted ypu could easily not use an elevated rail at all.

 

[TaperPin]

I vote for the 20 MOA based on one prairie dog shot years ago. He was a fatty, with the sun in his face and right in front of a pale patch of dirt that showed his form and impacts very well. He was also so far away that the cheap scope was dialed all the way up and he was quite near where the reticle runs into the tube. I would have paid a couple hundred bucks to have 20 more MOA.

Sworn statements of all the parties there that day differ in how many shots were fired at that one dog, but it was more than 50. Lol