FFP scope owners - What has been your technique in determining holdover?August 12 2017 at 9:57 PM
dave cole (Login tulsaairguns)
I hope this makes sense……
How are you that are using FFP scopes, determining how much hold over to use on a target beyond your zero?
I have been using Hawke Sidewinders for the last several years and they have served me well. Using Chairgun, I’ve been able to create accurate holdover charts for all of my guns.
I have recently purchased an Athlon Optics 6-24x50 Argos BTR Tactical Rifle Scope, FFP Ill. ATMR Reticle, 1/4 MIL wanting to dip my toe into the world of FFP scopes and see what kind of benefits they offer me, if any.
Obviously, the FFP as opposed to the SFP, there’s not graphs you can create (i.e. Chairgun, etc.) to refer to, estimating hold over for a given magnification because of the obvious differences between FFP and SFP.
As a point of reference, I zeroed my gun at 50y, shot at 100y and if it were Sidewinder, it would have been a 4 mildot holdover and with the Athlon, it was a 3 mildot. That said, Chairgun doesn't parallel holdover.
Are you guys testing at various distances for your results or is there an app or program that would allow me to generate holdovers?
I understand the mechanics and functionality of FFP scopes. What I'm needing to know is, how are you determining your holdover?
Thanking you in advance.
I'm not a FFP scope user, but I...
|August 13 2017, 1:54 AM |
know how ChairGun works and how to convert angles.
You can use the Generic Mil-Dot in ChairGun to model any reticle with constant subtension spacing. Let's assume that the ATMR reticle is a true MOA reticle:
A milliradian is 0.0573 degrees
An MOA is 0.01667 degrees
The magnification for a SFP Mil-dot scope is 10X. ChairGun varies the subtensions according to the "Scope Mag" setting.
The magnification for an FFP scope does not matter but you can use the "Scope Mag" setting to make the subtensions whatever you want.
If you want MOA:
10X x 0.0573/0.01667 = 34.4X
In ChairGun, choose the generic Mil-Dot reticle and set the "Scope Mag" to 34.4X.
34.4X should be the correct value for a MOA FFP scope, regardless of the magnification setting on the scope.
|This message has been edited by Scotchmo1957 on Aug 13, 2017 1:56 AM|
Strelok pro has a FFP reticle option
|August 13 2017, 2:57 AM |
And you can set the drag function to the diabolo dome function which is what chairgun uses.
I had a FFP scope and unless using Chairgun, I was not good at estimating with it
|August 13 2017, 8:38 AM |
Therefore, I didn't spend enough time with it, sold it, and went back to what I love most.
The alleged benefits of a FFP scope is the mil markers stay the same no matter the distance or magnification.
Well, I myself prefer the minimums on all scopes, which for me are all either 1.5x, 3x, 4x, or 6x Now, considering that most, (not all by far, Vortex is 14x, others are true at max power, you must ask manufacture, or put up a yard stick, marker at 100 yards) scopes have their true mil dots at 10x, I would (if able) consolidate all scopes for what would be my ideal, say 3x10x44 SWFA, Bushnell, decent glass, mil-quad marks true at 10x.
If all were the same, true at 10X, I could range estimate very precisely on that 10X setting. I'd still want to take my shots on 3x or 6x. If you know the distance to, and height of target from a known TRUE mil marker (3.6"@100yrds) you can do the math to convert what your holdover should be on any other power. Equal #'s are obviously easier, faster.
So, FFP is supposed to be the same 3.6" @ 100 yards at any magnification. I just find knowing my zero on scopes lowest power lets me do an amazingly array of accurate Kentucky windage shots once I know that zero, and the trajectory out to farthest shots made. Thus why I like a plowed field of dirt , a lake, a desert, for a visual report.
The other thing I enjoy about low mag scopes is the huge difference in FOV. At 150-200 yards, you can't even see the pellet hit at bottom of scope if scope is set on 10x on up and zero is what most of us consider normal. Having a near & far zero, knowing your apogee, and then applying mils or clicks. My current set ups are all zeroed at 32 yards, (my target set up) but I know where to set turrets or just use hold over out to 75 by heart.
Interesting example. Shooting a rifle I just sold. Testing it at 70 yards. Zeroed at 32 yards. I knew on 3x that one mil-dot down brought me close to 70-75 yards. I don't have a Chronograph nor did I spend much time with this rifle as it needed some work.
Same rifle, very next shot, set scope on 9X & I must use 4th mil-dot down to hit the same POA I had on 3x.
I honestly wish one could order up a certain reticle, turrets that match their air gun perfectly. As far as I know, a 1/10 mil-rad adjustment turret is nice for air guns. Maybe I should get another FFP scope and give it a try. they're too expensive though for me to just try. You always loose money in this hobby and even if it's mint in box, never mounted at all, one would be lucky to get 3/4 value shipped if sold.
If I found a FFP scope that was say 1.5x4x40, or 3x9x44 and mils were true throughout that entire range, I'd definitely like to unify all my scopes and know them better. If scopes were all equal, only difference would be pellet weight, speed, BC. It would be easier than figuring out all the scope stuff also.
Hawke AMX reticles are nice. If you explained your rig, its' caliber, weight of pellet & speed, farthest shots you'll be taking, we all might be able to explain if a FFP scope is worth the price or if a decent 2nd with a doped out elevation target turret would be easier.. If you're not a good range estimator, a good scope can do that; but a regular Bushnell, or Nikon rangefinder will be more than good enough for most of us.
Hey Dave, I'll be watching the data inflow on this. As you....
|August 13 2017, 12:56 PM |
may recall I had this exact same scope on my Vulcan in May when we were
hunting PD's up in South Dakota. I'm still not real confortable with the
FFP & the ranging peculiarities yet.
With that said, I really like the scope...
|August 13 2017, 2:13 PM |
I have two Athlon FFP scopes. I determine the hold over for each distance, cover the front objective cap with masking tape, draw a reticle, and label the different distance aim points. With FFP, it doesn't matter what power you're on, the aim points are the same.
I made my own side wheels and mark them in yardages based on focus. With the front cap opened I can see my reticle chart. So focus, read yardage, glance at chart, and take aim.
The two scope I have did not focus at 10 yards at high power but a slight loosening of the objective ring brings it into focus.
X-2 what Michael said
|August 13 2017, 2:56 PM |
The fact that subtention does NOT change with magnification changes is the beauty of First Focal Plain
scopes. The only issue is that all the dots,crosshairs and other rangfinding reticle artifacts get thicker with increases in magnification power settings. So for field Target and many other "target" sports a crosshairs with SMALL CIRCLE (DONUT) in the center keeps the actual target visible.
Pray for snow during hunting season!!!
My thoughts (long winded!)
|August 13 2017, 3:56 PM |
I hope I'm not the only one who finds this discussion confusing. So let me ad my experiences into the mix. I use mid-dot scopes so my references will be to mil-dots. 1 1mil-dot at 100 yds measures approx 3.6 inches, 1 MOA at 100 yds measures approx 1 inch. This discussion assumes you are working up a ballistic chart of holdovers using the markings on your reticle (subtentions as Scott said)
For the average shooter there is only one critical thing you have to know about First Focal Plane (FFP) vs Second Focal Plane (SFP) scopes. For FFP Scopes the size of the reticle grows and shrinks with changes to the power setting, but at a given distance regardless of the power your scope is set at 1 mil-dot will measure 3.6 inches at 100 yrds (or 1.8 inches at 50 yds). For SFP scopes the size of the reticle remains constant regardless of the power setting of the scope but the distance measured by one mil-dot at 100 yrds will be different for each power setting. If your SFP Scope is calibrated to measure true mil-dots at 10x then with a 10x setting at 100 yds 1 mil-dot will measure 3.6 inches but at 20x 1 mil-dot will measure 7.2 inches.
So how does this affect your trajectory (it doesn't) and your ballistics charts (significantly). if you use a FFP scope (or a fixed power scope) you will need only ONE trajectory chart for your rifle as one mil-dot measures the same distance at fifty yards whether using 3x or 5x or 50x. So if you know your rifle shoots 1.8 inches low at 50 yds you know you need to hold 1 mil-dot over the target at 50 yards no matter what the power setting. Your mil-dot hold offs are fixed to your inch hold offs at every power level.
With a SFP scope, if you are anal, you would need a trajectory chart for each scope power that you would want to shoot at. Shooting the same rifle as referenced above and using chair gun to illustrate with a Hawke 20x 1/2 mil-dot reticle shooting at a target at 50 yds your SFP hold overs would be 1 ml-dot at 20x, .50 mil-dots at 10x and 1.62 mil-dots at 32x. Depending on the size of your target these are significant differences. Your mil-dot hold offs vary differently from your inch hold offs at each scope power level.
So what does this mean to you as an owner of one of these type scopes? My thoughts are if you are a competitor and must shoot precision shots at varied but measured distances and you need to use your reticle to measure your hold offs, your best choice is a FFP scope or shoot a SFP scope at only one power setting. You will work up one ballistic chart with mil-dot or MOA hold overs which will work at all distances. Once a target is ranged your ballistic chart will tell you the exact subtension to hold on your target.
If you are a hunter or a plinker and you shoot Kentucky windage frequently at varying scope powers then any of them will work given your ballistic chart is set up in inches. Why, because when you shoot the same rifle we mentioned above you know it shoots 1.8 inches low at 50 yds, this remains true regardless of what type of scope or what reticle you are using. So when you look through your scope at a tin can that you ranged or guesstimate to be 50 yds your brain calculates what 1.8 inches is and you hold your cross hairs over that amount. Your ballistic chart will show your holdovers in inches and your mind will calculate where to put the cross hairs based upon what it sees.
One important point about FFP scopes if you shoot a lot at lower powers make sure you check out the scope you intend to buy and look through the reticle at 3x and 4x. With some of the fine cross hair reticles the mil-dot markings are pretty much useless below 8x. Also when working with ChairGun or Strelok remember if you have an FFP scope the scope power settings are meaningless and should be left alone.
So for me the answer is if you want your ballistic chart to decide where you need to hold for a shot then the FFP option is the best. When out hunting with a FFP scope all I have to do is range a target, look at at my holdover chart pick up my rifle and shoot, no matter what power the scope is sitting at. With a SFP scope you would additionally need to dial the scope to your chart power or pull the chart for the power you were on. If you were using KY windage it gets even messier and more time consuming.
So to sum it up, for FFP your reticle changes with power changes but your mil-dot ballistic chart remains the same, SFP your reticle remains a fixed size but your mil-dot ballistic chart is different for every power setting. I have used both in competition and hunting and they both worked well. If I had the option today all my scopes would be FFP.
Hope this helps, I see Mike and Ski added some less winded advice while I was working this up. If you made it this far congratulations.
Jim in Sacramento
OK, I figured out how to utilize the SFP Chairgun app to a FFP scope.
|August 14 2017, 12:34 AM |
OK everyone I got it figured out. And BTW, thank you for all your input it was well received and some of it applied.
Here's what I did......
I used targets found at mytargets.com with 1" grid and 1/4" dots.
Zeroed for 50 yards.
I moved the target out to 100 yards using my range finder to insure the distance.
I shot three times using the 3 mil dot holdover. the difference between the POA and the POI was 2 1/4" low. This distance between the POA and the POI though it may seem small at 100 yards can mean an easy miss at distances beyond the zero (50 yards).
Here is where I applied the Chairgun app........
I had all of my ballistic data plugged with the zero set at 50 yards. I selected the 10x 1/2 mil dot reticle because I wanted to be able to use the half mildots that the Athlon utilizes as well as the Hawkes.
I placed the target at 100 yards and shot three times using a 3 mil dot holdover. I measured the difference between the POA and the POI. The difference was 2 1/4" (about a half a mil dot)
Chairgun showed the 3 mildot holdover to be only 92 yards but I needed it to show 100 yards.
Why not just use the 3 1/2 hold over as my holdover and call it good you might ask?
Because when measured, the POA and the POI was a little over 2" difference and when applying the Chairgun app it would make every POA different from the POI except, of course, zero. And in order for the reticle view to be accurate regardless of of distance to target, POA and POI have to be the same. After all, isn't that the idea?
Here is how I was able to "manipulate the Chairgun app to get the desired results.
Going to the reticles tab on the app, I selected the POI tab (important to do the math) located in the lower right corner of the page. This brings up the drop of the pellet in inches at a given distance. I compared the distance shown of the POA compared to the POI. 2" in this case.
Next, in the same reticle view tab in the upper right hand corner is a "Mag" tab where you can change the magnification, which, when use a SFP scope will change the distance to holdover.
Key factor here:
For FFP scopes this really doesn't matter because as the magnification changes so does the size of the reticle. Ultimately, your holdover will always be the same regardless of the magnification; the very cool feature of a FFP scope and this amplifies the importance of the POA and POI being consistent regardless of distance to target.
I determined that by changing the magnification from 10x to 8.6x (in trial and error) I was able to get the POI to match the POA at the 100 yards. Then, I test shot all mildots and half mildots between the zero and 3 mildots and it was spot on.
Why didn't I go more than 3 mildots you may ask?
That's easy; I don't have but 100 yards at this particular range I was at to do this test.
This may sound like it took all day but in fact, it took longer to type this explanation that it did to achieve the results.
So...The key to getting the Chairgun app which is intended for a SFP scope to work with a FFP scope, you may need to manipulate the magnification of said reticle to match your POA to the POI.
I'm sure that I lost most of you about 3 sentences into this explaination. Unless you have a scope where the POI and the POA aren't the same when using the Chairgun app, this won't make a whole lot of sense.
And for the "scope purist" out there.... relax. 10x or 8.6x it works and at the end of the day that is all that matters....
Only thing you lost me on is Chairgun having 10th's
|August 15 2017, 6:28 AM |
on their magnification settings. You mentioned 8.6 = to 10 power. I did not know you could vary the magnification by 10th's. Is this a pro version you paid for? I only knew of basic #'s like on a scope. They are marked throughout their range. 3,4,5,6, so on. Yes, you can turn that knob 1/2 way between 5 & 6, and basically you know you're at 5.5 power. I didn't know Chairgun had this feature.
JD I have the free phone app. Tap on the mag selection button, enter
|August 15 2017, 2:56 PM |
The desired value with the decimal point.
i.e. 8.3 or 6.1 etc.