Adjustable Scope Mounts
– Eratac & Ivey –
Rifle scope mounts are decisively important – they make you or break you. Adjustable scope mounts like the Eractac or the Ivey Mount take it a step further. Adjustable scope mounts like these enable us to change our base zero by building in further adjustment in the scope base on the fly. In essence we are increasing the angle of the rear part of the base, the reticle moves further down on your target so you will have to point the barrel up higher therefore adding more elevation. For those of you that have been in long range shooting for sometime, we all remember the discussions around the amount of built in angle in MOA/Mils required in our base and the headaches some would have in getting their setup right. Those days are somewhat gone.
However do not underestimate the usefulness of simply bore sighting your rifle and scope. It will already show you whether you will be able to zero your setup way before you head to the range as well as giving you a very good idea of how much scope travel you are going to be left with after zeroing your rifle. If you want to learn more about how to setup your scope head to this article
What do we need Adjustable Scope Mounts for?
Many shooters would have 20,30 or even 40MOA built into their base to enable them to reach the distance they were after. In a nutshell, scopes offer limited amount of travel. This has improved over the years somewhat, however 70-120MOA tends to be where most scopes are. If your scope turrets are mechanically centered as they ideally should be, you would be left with a little over half that elevation travel by the time you zero your rifle. That means you may be left with 35-60MOA of elevation with most scopes today. The traditional bases with built-in MOA would help you offset some of this. Let’s say you had 50MOA left in your scope after zeroing and you add a 20 MOA base, you are now armed with 70MOA of vertical travel. Sufficient? Depends what you’re after and what rifle / cartridge you’re shooting. If you have too much angled built into the base, you may not be able to zero your rifle at 100m/yds.
Not a big deal but good to be aware of it. We have one particular 300NM rifle that is zeroed at 600m. Our near 100m zero is about 10.5MOA high. We then simply input this offset in kestrel which will deduct that amount from the dope it will give us. Out to 600m, it will give us a negative value (hold under).
Enter the adjustable scope mounts.
Adjustable scope mounts enable you to go from 0 MOA to their maximum amount of travel in just a matter of seconds. The Eratac adjustable mount enables you to go from 0-70MOA by turning a knurled wheel which rotates this eight-sided irregular hexagon which in its every movement, adds 10 MOA to your base. Pretty cool isn’t it? Indeed it is and the Eratac works very well. It’s made for various scope tube dimensions including the popular 30mm tube and 34mm tubes. Seen below, we mounted a Vortex razor genii 4.5-27×56 to boost the 78MOA available on this scope. After we zeroed our rifle, we were left with about 50MOA. (sufficient to shoot a 300NM to 2kms in most weather conditions) however if we wanted to shoot even further, we could crank on an additional 70MOA. Remember, past its supersonic range, the drop of the bullet will increase FAST and will eat up your vertical travel easily.
Above: Eratac 34mm. Notice the knurled wheel which is used to adjust the elevation settings with. In this configuration, I had 78MOA on the vortex and 70MOA on the Eratac for a total of 148MOA of vertical travel plus the hold over possibility offered by a reticle such as the EBR7C shown below.
Adjusting the Eratac – video clip
It’s simple, you need to loosen the front and rear screws, takes about 3 turns with a screw driver and then it enables you to turn the knurled wheel. Once you set the amount you are after, simply retighten those front and rear screws again and you’re ready to rock those far away targets. The idea here however perhaps is not that you will be adjusting this in between shots during a match, but rather it enables you to get the setup right where you want it to.
Otherwise adjust it to 70MOA to enable you to reach way out there essentially supplementing your scope with a further 70MOA. To use the example I’ve already mentioned, let’s say I was left with 50MOA after zeroing my rifle at 100m/yds. You may now adjust your Eratac adjustable mount to 50MOA and dial the difference on your scope turret to continue where your scope previously came short. In essence this means you now have 100MOA of available travel.
Above, Ivey adjustable mount (0-200MOA) sporting a March 5-40×56. Beneath the Eratac Adjustable Mount (0-70MOA)
I have setup the Eratac against a tall target at 50m to check that it is repeatable and consistent being very careful not to move my setup. I mounted it onto a rail and mounted the rail in a vice. The base is indeed repeatable and the reticle moved up and down ten times coming back down to my original zero.
I also tried dialing in 70 MOA on my scope turrets to see the reticle move downwards on the tall target to a specific point. Then I had someone mark that point for me on the tall target. I know that point is now 70MOA of travel. At this distance you can do it very accurately on 20x mag. I then adjusted the scope turret back to zero so that the reticle would climb back up to my starting point. I then adjusted the Eratac to 70MOA so that I would see the reticle climb down the tall target test to the same point where it had been when I adjusted my scope turrets. That’s a confidence builder.
The Eratac adjustable scope mount is fairly light, weighing in at 430grams for the version I have, 34mm tube 30mm height. On top of the rings, you will find 4 additional screws that enable you to mount other sights for close range work.
(picture source: https://twobirdsflyingpub.wordpress.com/2014/01/29/shot-sow-2014recknagel/)
Ivey – Eratac on steroids +specs
What would be better than the Eratac? If you want to reach out further and do not want to carry any tools, the Ivey might just fill your ticket if you want a turret adjustable scope mount. It also weighs more than twice the Eratac. (907grams vs 430grams for the eratac) and comes at about twice the cost here in Europe.
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The first impressions unboxing the Ivey, it’s chunky, like a military scope. It feels solid. There is more meat around the rings and the rings are wider. Each ring is secured with 6 screws rather than 4 although I’m pretty sure no scope is moving in any of these setups. Harry from Solid Solution Design in the Netherlands has tried it on his DTA 416Barrett 40inch barrel rifle and he reports no issues. Like me, Harry travels a few hundred miles each way to get shooting these ELR rigs so if it didn’t work for him, it wouldn’t sit there. I wasn’t sure which one would work for me so I got them both at different time intervals.
Below you may see the two mounts as you would sitting behind your rifle. They are almost of the same height, about the height of a 375cheytac case actually shown there. I mounted a March 5-40×56 FFP scope with an FMA-MT reticle illuminated. (review coming) This is basically the same reticle available in the Genesis ELR scope. I am a March scope fan so I wanted to use this FFP scope on my 33XC build. This scope model has 78MOA of internal travel which is why I coupled it to the Ivey. This model was fitted with the FMA-MT on request and so far, i’m very happy about it. It’s a very fine reticle, reminds me of the NPR1 reticle on the Nightforce BR scopes series. For fine holds at ELR distances, it should be fair game.
There is a built in bubble level in the Ivey scope mount too which is always nice to see. So when do you need an Ivey Scope mount with upto 200MOA (60Mils)? Well definitely it’s for ELR shooting. Kestrel numbers indicate that shooting the new 33XC to 2 miles will require a pretty push that would make my math teacher envious. We’re looking at about 190-210MOA depending on the atmospherics. That means we can virtually dial up to 180MOA on the ivey and add 10-20MOA on the scope. The Ivey side turret for elevation is marked in 5 MOA increments with 2.5MOA hashmarks in between.
Ivey Clicks: You can feel that you are going past each 2.5MOA increment. It doesn’t click like a scope turret but you feel a nudge past each hashmark and there is no discernable play. Every turn forward will move the scope 50MOA up. For our 2 mile shot, we need 3 turns plus 30MOA. Ivey suggests that you go past your intended adjustment and come back when dialing in your setting. Then tighten the locking nut again.
Here is a quick video to help you visualize the clicks. I cranked on 70MOA to compare to dialing in on the Eratac.
NEXT – TEST return to Zero.
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