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CAVU

Reticle adjustment and scope mount slope

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The US Optics specs. for the FDN FX10 scope list a total elevation travel of 100.8 MOA. The JBM ballistics calculator says at 1000 yds. the Hornady 6.5CM,147 gr. ELD cartridge would require 30 MOA drop adjustment from a 100 yd. zero. I’m thinking I should use a 30 MOA canted scope mount to position the reticle in the center of the optics glass at 1000 yds. while still allowing a 100 yd zero. Before I potentially make an expensive mistake I felt I should seek some advice. I’m all ears. Thanks. 

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31 minutes ago, CAVU said:

The US Optics specs. for the FDN FX10 scope list a total elevation travel of 100.8 MOA. The JBM ballistics calculator says at 1000 yds. the Hornady 6.5CM,147 gr. ELD cartridge would require 30 MOA drop adjustment from a 100 yd. zero. I’m thinking I should use a 30 MOA canted scope mount to position the reticle in the center of the optics glass at 1000 yds. while still allowing a 100 yd zero. Before I potentially make an expensive mistake I felt I should seek some advice. I’m all ears. Thanks. 

I'll answer this in colors.  #1.MOA sucks.  Let's move beyond that, though.

If it's 100.8 MOA of total elevation travel, that's 50.4 MOA UP and 50.4 MOA DOWN, on a zero-MOA mount.  Should be, anyway.

My .260 Rem with a Hornady 147 ELD-M handload, pushing 2650fps MV, runs a 100 yard zero.  It's 8.5 mils of drop to 1000 yards.  Confirmed, at 1000 yards.  mils to MOA = x 3.4377. 8.5 mils x 3.4377 = 29.22 MOA.  I'd say that your information is pretty damn accurate, and the Hornady 147 6.5CM ammo is pushing 2650fps.  No other way around that data.

Why would you want to do this?  That's setting the very center of your scope up for a 1000-yard ZERO.  And that info isn't even correct.  You have 50 MOA UP and DOWN with the internal travel of that scope, as stated.  You can use a zero-MOA mount, and still make 1000 yards easily.  Just dialing. 

Check it out.  I have a LaRue LT-158 mount on my .260.  That's 10 MOA built into that mount.  MORE than what I'll ever need, with my internal scope adjustments.  My load is supersonic to 1500 yards.  At that distance, I'm 17.2 mils of drop.  For your case, multiply that by 3.4377 to get the MOA equivalent... That's 59.12 MOA, to 1500 yards...   You can almost DIAL 1500 yards with that scope, with a zero-MOA mount...

You don't NEED a 30-MOA mount, not at all.

More on this story...  These 6.5s (both Creedmoor and .260 Rem) have a very similar flight path as a good/great 300 Win Mag round.  I'm rolling some pretty serious 225gr Win Mag loads, through a bolt gun.  I have a 30 MOA mount on that gun.  Different scope, but the internal travel limitations on that scope leave me with nothing less than a 500-yard zero.  So, it has a 500-yard zero. My goal for that load was to keep it supersonic to a mile.  The 30-MOA mount and 500-yard zero keeps that load supersonic to 1800 yards - achieved my goal.

Had to work out a 2-mile solution for a .375 CheyTac bolt gun.  Best I could do was an EIGHTY-MOA (80 MOA) combination for the scope mount, to keep it supersonic to 2300 yards.  It's all holding, after that, to 3520 yards... 

I think you're reading into this scope-travel and MOA-mounts more than you need to... 

Edited by 98Z5V

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6 hours ago, 98Z5V said:

I'll answer this in colors.  #1.MOA sucks.  Let's move beyond that, though.

If it's 100.8 MOA of total elevation travel, that's 50.4 MOA UP and 50.4 MOA DOWN, on a zero-MOA mount.  Should be, anyway.

My .260 Rem with a Hornady 147 ELD-M handload, pushing 2650fps MV, runs a 100 yard zero.  It's 8.5 mils of drop to 1000 yards.  Confirmed, at 1000 yards.  mils to MOA = x 3.4377. 8.5 mils x 3.4377 = 29.22 MOA.  I'd say that your information is pretty damn accurate, and the Hornady 147 6.5CM ammo is pushing 2650fps.  No other way around that data.

Why would you want to do this?  That's setting the very center of your scope up for a 1000-yard ZERO.  And that info isn't even correct.  You have 50 MOA UP and DOWN with the internal travel of that scope, as stated.  You can use a zero-MOA mount, and still make 1000 yards easily.  Just dialing. 

Check it out.  I have a LaRue LT-158 mount on my .260.  That's 10 MOA built into that mount.  MORE than what I'll ever need, with my internal scope adjustments.  My load is supersonic to 1500 yards.  At that distance, I'm 17.2 mils of drop.  For your case, multiply that by 3.4377 to get the MOA equivalent... That's 59.12 MOA, to 1500 yards...   You can almost DIAL 1500 yards with that scope, with a zero-MOA mount...

You don't NEED a 30-MOA mount, not at all.

More on this story...  These 6.5s (both Creedmoor and .260 Rem) have a very similar flight path as a good/great 300 Win Mag round.  I'm rolling some pretty serious 225gr Win Mag loads, through a bolt gun.  I have a 30 MOA mount on that gun.  Different scope, but the internal travel limitations on that scope leave me with nothing less than a 500-yard zero.  So, it has a 500-yard zero. My goal for that load was to keep it supersonic to a mile.  The 30-MOA mount and 500-yard zero keeps that load supersonic to 1800 yards - achieved my goal.

Had to work out a 2-mile solution for a .375 CheyTac bolt gun.  Best I could do was an EIGHTY-MOA (80 MOA) combination for the scope mount, to keep it supersonic to 2300 yards.  It's all holding, after that, to 3520 yards... 

I think you're reading into this scope-travel and MOA-mounts more than you need to... 

ABSOLUTELY!

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Depends on where you want to zero and what that'll cost you in elevation travel, or equally likely you could gain a lot of elevation travel and not need it. The easiest way to figure this out is to find out how much elevation travel you're left with after getting your zero established with a standard set of unadjusted mounts.

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My objective is to be viewing through the center of the optics glass lenses at 1000 meters.  I would then adjust down 10.4 mils for a 100 yd. zero and set the zero-stop there. The 10 mil canted mount would position the reticle in the best location for optical quality at the 1000 meter range allowing for both a 100 yd. zero and a 1300 meter (transonic) adjustment leaving a few mils adjustment available on both sides. Thanks to both of you for the  help. I’m learning this all for the first time. 

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28 minutes ago, CAVU said:

My objective is to be viewing through the center of the optics glass lenses at 1000 meters.  I would then adjust down 10.4 mils for a 100 yd. zero and set the zero-stop there. The 10 mil canted mount would position the reticle in the best location for optical quality at the 1000 meter range allowing for both a 100 yd. zero and a 1300 meter (transonic) adjustment leaving a few mils adjustment available on both sides. Thanks to both of you for the  help. I’m learning this all for the first time. 

You have to crawl before you walk. The 100 yard zero comes first, that's what will tell you how much elevation adjustment will be either consumed or added to your available adjustment. After that, how much you will need to get out to 1000 meters will depend on your actual ballistic performance and environmental factors, not what a calculator spits out for an assumed set of conditions.

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Duly noted. The 10 mil mount should give me a few mils of adjustment above the zero range (100 yds) and on the other side past the transonic range (1350m). Do you think I’m wise to drop several hundred dollars on a 10 mil canted mount (Spuhr, Desert Tactical, LaRue etc) then develop my calc forms and know I’ll have some leeway for environmental conditions and different loads etc. I’m anticipating 2K for the scope and around $300 for the mount and wanted to make sure I’m understanding this “stuff “ correctly. I appreciate your help. 

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I like it!.  I’ll have to check the dimensions of the scope turret mechanism. The website says not compatible with the USO T-PAL scope but I’m interested in the USO FX10 and it may fit. The tritium illuminated anti-cant bubble is neat. Thanks for the info. 

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9 hours ago, CAVU said:

 Do you think I’m wise to drop several hundred dollars on a 10 mil canted mount

I'd just drop $160 on the LaRue mount, and be done.  LT-158 mount, select 30mm (if that's your scope), select "VFZ Mount" and that drops the price from $210 to $160.  You don't "need" the QD levers on this gun, just go with the VFZ mounting option.  They even give you the sweet little wrench to tighten it up.

Now that I cut your mount budget in half - figure out what you're gonna do with all the extra money...  :thumbup:

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12 hours ago, CAVU said:

My objective is to be viewing through the center of the optics glass lenses at 1000 meters.  I would then adjust down 10.4 mils for a 100 yd. zero and set the zero-stop there. The 10 mil canted mount would position the reticle in the best location for optical quality at the 1000 meter range allowing for both a 100 yd. zero and a 1300 meter (transonic) adjustment leaving a few mils adjustment available on both sides. Thanks to both of you for the  help. I’m learning this all for the first time. 

You're going about this completely backwards.  It looks like you're basing everything off a 1000 yard zero.  You'll be doing everything backwards of what most distance shooters do.   You'll only confuse yourself, when you're trying to talk to other people about this, and it'll leave you frustrated as hell, because everyone you talk to about distance shooting will think you're (a) confused as hell, or (b) an idiot.

If you HAVE the travel in the scope, zero for the shortest distance you can - you're WAY more accurate, and "adjustable" at the shortest distance that you can accomplish. Then, later, you get better at distance, and you dial your 1000 yard shot and hit it.  We have ALOT of people here that shoot 850 yards routinely, 1000, 1100, and 1200 yards on occasion.  600 yards is child's play, but at 800 yards, you better start REALLY paying attention to wind.  You have any idea the size of the target you'd need to ZERO a gun at 1000 yards?...  You need a crew of people downrange, at 1k yards, doing THIS for you...

2012-camp-perry-pits1.jpg

I think you're trying to complicate shiit, with complicated shiit here.

You have the travel in the scope.  Just zero the thing at 100 yards, and work yourself up to the distance that you want, 1k yards.

Zeroing my .300 Win Mag at 500 yards SUCKED.  It was a chore.  My mount solution to get me over a mile supersonic left me no other choice.  It SUCKED zeroing at that distance. 

Aim small, miss small.  Your best chance of doing that is the shortest, most common-sense diatance that you can.  100 yards is pretty much the common distance.  You have enough scope to dial this whole thing to 1k yards. 

You can take that FWIW...   :thumbup:

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I don’t think I’ve done a very good job of explaining my objective. More importantly I’m not sure if this should even be an objective of mine. Sorry.

In a nutshell;

Mount the scope and zero at 100 yds.

Use a mount with a tilt as close to my 1000 yd drop calculation (10.2 mils) as possible.

The desired result:

4 mils adjustment remaining after 100 yd. zero in one direction.

3.8 mils adjustment remaining after the 1000 yd. adjustment in the other direction.

Erector tube centered for the 1,000 meter target providing optimal scope clarity (an attempt to get the most from a fixed 10x scope).

Scope: US Optics FDN-FX10, 28 mil total elevation adjustment. I do like the LaRue LT-158 mount. Thank you 98Z5V. I’ve listened to all of you and am thinking “just go buy something and start shooting” I think part of my reluctance in all this is due to the variety of DPMS gotcha’s a first time builder is warned about. Thanks for helping a beginner whose never even looked at a 1,000 meter target let alone shot at one... Yet!

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16 minutes ago, CAVU said:

I don’t think I’ve done a very good job of explaining my objective. More importantly I’m not sure if this should even be an objective of mine. Sorry.

In a nutshell;

Mount the scope and zero at 100 yds.

Use a mount with a tilt as close to my 1000 yd drop calculation (10.2 mils) as possible.

The desired result:

4 mils adjustment remaining after 100 yd. zero in one direction.

3.8 mils adjustment remaining after the 1000 yd. adjustment in the other direction.

Erector tube centered for the 1,000 meter target providing optimal scope clarity (an attempt to get the most from a fixed 10x scope).

I submit the following as my first bullet point:

tenor.gif

 

Having had my fun, let's address the practical aspects of what you want to do.

#1. Optical clarity in a fixed power scope:

U.S. Optics utilizes excellent glass, clarity at any distance shouldn't be an issue, assuming your eye relief is correct and you can adjust parallax.

#2. Total elevation adjustment:

Let's utilize the 100 MOA of available elevation adjustment travel for the sake of example; Let's say your scope shipped to you with the reticle centered in it's range of travel, 50 MOA of available adjustment in either direction. With standard non angle-adjusted mounts, your reticle would theoretically appear 2.5" above the line of sight defined by the centerline of the bore, assuming everything was mounted correctly. Even if we assumed no bullet drop between the muzzle and your 100 yard sight-in target, you just lost 2.4 MOA of available travel to your zero, plus the actual bullet drop.

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I read that having a scope reticle adjusted to at or close to it’s limit is not the optimum setup from a clarity and distortion perspective. I have no idea if it is true or not. That is the genesis to all these questions of mine. I appreciate the humor. 

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25 minutes ago, CAVU said:

I read that having a scope reticle adjusted to at or close to it’s limit is not the optimum setup from a clarity and distortion perspective. I have no idea if it is true or not. That is the genesis to all these questions of mine. I appreciate the humor. 

I appreciate you taking it in stride, a sense of humor goes a long way towards avoiding frustration with long range shooting concepts.

Carrying on from point #2 above:

Let's say just for kicks that after compensating for drop and your 2.5" scope height, your total elevation adjustment for coincidence of point of aim (POA) and point of impact (POI) is 3.5 MOA. Subtract that from your 50 MOA available for adjustment and now you have 46.5 MOA of adjustment left to get you out to the 1k mark. 

Not a problem with the 6.5 Creedmore  to get to 1k with 46.5 MOA available on the dial.

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So now let's assume you bought the 30 MOA mount thinking you couldn't do without it. You decide to laser bore-sight and you put and put an 18" square sight-in target at 100 yards. You put the laser dead on the bullseye and look through the scope only to find out that you're looking at a point ~19" under the bottom of the target and you've got about 28" of adjustment to dial, just to get a bore-sight shot, not to mention the possibility that you might get a low hit and have to adjust even more elevation. 

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11 hours ago, Matt.Cross said:

So now let's assume you bought the 30 MOA mount thinking you couldn't do without it. You decide to laser bore-sight and you put and put an 18" square sight-in target at 100 yards. You put the laser dead on the bullseye and look through the scope only to find out that you're looking at a point ~19" under the bottom of the target and you've got about 28" of adjustment to dial, just to get a bore-sight shot, not to mention the possibility that you might get a low hit and have to adjust even more elevation. 

Your scenario is exactly what I would expect. I would then dial the 29.3 MOA (50.4 available) correction to zero at 100 yds. This should place the center of the erector tube approximately half way (58%) out from the center of the optics lens. Now zeroed at 100 yds. I calculate for a 1000 yds.   (~30 MOA) and dial in; moving the reticle/erector tube to the center of the scope tube allowing the long range shots to be view through the center of the optics lens. I think😟

p.s. Thanks for the link mrmackc I’m getting a little better every day. 

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10 minutes ago, CAVU said:

Your scenario is exactly what I would expect. I would then dial the 29.3 MOA (50.4 available) correction to zero at 100 yds. This should place the center of the erector tube approximately half way (58%) out from the center of the optics lens. Now zeroed at 100 yds. I calculate for a 1000 yds.   (~30 MOA) and dial in; moving the reticle/erector tube to the center of the scope tube allowing the long range shots to be view through the center of the optics lens. I think😟

p.s. Thanks for the link mrmackc I’m getting a little better every day. 

Pardon me for being slow to catch on to your meaning. You're speaking of 'direct dialing' for elevation rather than a reticle holdover, I get that now. You still need to know that your direct dialing will have to be adjusted for your load's real-world performance. The calculator will only get you close. :thumbup:

You still don't need an angle adjusted mount to get from 100 yards to 1000 though.

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34 minutes ago, Matt.Cross said:

Pardon me for being slow to catch on to your meaning. You're speaking of 'direct dialing' for elevation rather than a reticle holdover, I get that now. You still need to know that your direct dialing will have to be adjusted for your load's real-world performance. The calculator will only get you close. :thumbup:

You still don't need an angle adjusted mount to get from 100 yards to 1000 though.

Thank you Matt.  Understood.  I’m thinking it wouldn’t hurt to have the best optical quality at the range I’m hoping to get proficient at.  I sure won’t have the scope to use as an excuse!  This correspondence is literally the first time I’ve ever done anything like this. I’m learning that it’s difficult expressing concepts especially semi-technical subjects. Everyone’s patience and advice is appreciated. 

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17 hours ago, CAVU said:

Scope: US Optics FDN-FX10, 28 mil total elevation adjustment.

So, this is a Mil scope and not an MOA scope that we're talking about here.  Too easy, in my case.

You have 14 mils UP and 14 mils DOWN that you can dial with a zero-MOA (straight) scope mount.  Straight up dial.  You'll change that 50/50 bias in mils by about 3, just going to a 10MOA mount.

My .260 Rem is 8.5 mils of drop at 1000 yards.  Your 6.5 Creedmoor should be pretty close to that.

You could run a straight mount on that, and still be plenty fine at 1000 yards.  A 10MOA mount would give you a little bit more, to go further distance later.

Wind is gonna be your biggest problem at 1000 yards - not that scope.  If I straight dialed 14.2 mils on that .260 Rem gun, that would have me at 1350 yards.  3/4 mile.

You'll be fine with that scope, it's clarity, and the LaRue LT-158 mount.  :thumbup:

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1 hour ago, Cunuckgaucho said:

@CAVU some good reading in this thread  https://forum.308ar.com/topic/18456-long-distance-getting-started/?tab=comments#comment-290032 plus some of the YouTube channels shown have further material.

 

Thank you for the thread. I unfortunately fall in to the bookworm category for now. I’ve watched Rex’s entire Sniper 101 series...twice. My rifle won’t be finished for a while but I’m trying to get prepared as much as possible. It’s been enjoyable learning from all of you. 98Z5V doesn’t need to worry about me walking onto the range a critiquing anyone. My 39 years of commercial flying, instructing and administrating check-rides has exposed me to plenty of bookworms. I’m the greenhorn now. 

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16 hours ago, CAVU said:

Thank you for the thread. I unfortunately fall in to the bookworm category for now. I’ve watched Rex’s entire Sniper 101 series...twice. My rifle won’t be finished for a while but I’m trying to get prepared as much as possible. It’s been enjoyable learning from all of you. 98Z5V doesn’t need to worry about me walking onto the range a critiquing anyone. My 39 years of commercial flying, instructing and administrating check-rides has exposed me to plenty of bookworms. I’m the greenhorn now. 

You'll get it - it just takes time and money.  Seriously.  Lots of time out there shooting, even with wind, and lots of money for ammo to keep practicing.  The important part is just getting the steps in the right order - logical progression.  You jump in too far, too fast, without a grasp on it, and you'll be miserable and give it up in no time.  Going to a course would help, I'm not joking.  That shortens your learning curve with great classroom training backed up immediately with practical experience, of what they're training you on.  Seems expensive when you look at it initially (course prices), but it will easily take twice that course-price in ammo and time to replicate what they're giving you, and retain it in your head.   :thumbup:

Edited by 98Z5V

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