GTA

All Springer/NP/PCP Air Gun Discussion General => Air Gun Gate => Optics, Range estimation & related subjects => Topic started by: Cableaddict on June 04, 2021, 09:54:18 PM

Title: Please help me calculate short-range adjustments !
Post by: Cableaddict on June 04, 2021, 09:54:18 PM
Man, I thought I had a handle on this, but my brain sort of took a vacation tonight.    :P

-----------------------------

I'm trying to decide between the two MTC Swat scopes,  10x32 and 12X50.
A huge factor for me,  because I both hunt small game and also do a lot of VERY short-range pesting,   is the amount of adjustments needed when switching from very near to med-far range. That includes both holdover & turret adjustments.   If the 12X50 doesn't require too much more finagling, I'd love to have the extra magnification & light gathering.
 
Obviously, the scope's height above bore is a critical factor.
I managed to get the numbers for these scopes today:  Height above bore is ~  3.00" for the 10x32, and 3.25" for the 12x50.  (Both are unfortunately on the high side, I guess due to the SWAT's adjustable mounts. )

OK, so I wanted to run the numbers, using a ballistics calculator.  I don't have any software so I just use the online calculator at American Airguns.
Thisun' here:
http://airguns.net/trajectory.php (http://airguns.net/trajectory.php)

But I'm stuck.  Something doesn't seem right with the numbers I got, plus I can't figure out how to calculate the holdover.  (I used to know, but my brain has evidently left for Bora Bora.)   I'll post the turret values in a second post, since the picture might be a bit large.   I'm puzzled as to why the bullet drop changed slightly, when the only input-number I changed was the scope height.  Why would that change the PHYSICAL trajectory?  Something seems off, so I don't trust the turret numbers I'm seeing here.

Anyway, the other problem is holdover, and maybe I screwed up the "MOA" parameter?    My current scope has mil dot specs, but the calculator asked for "clicks/MOA."     Thw SWAT scopes have 42 clicks per rotation, so I of course input that,  but their specs say 6 MILS per turret revolution.  Doing a calculation, that equals about 20 mils per rotation.   Is that the correct number to input into this calculator?

And even if it is, how do I then figure out how much holdover I'd need at 6 yards, assuming a 21 yard zero?
Title: Re: Please help me calculate short-range adjustments !
Post by: Cableaddict on June 04, 2021, 09:55:44 PM
Here's the two sets of numbers I got.  Again, it seems odd that the trajectory itself would have changed:

Title: Re: Please help me calculate short-range adjustments !
Post by: Roadworthy on June 04, 2021, 10:56:17 PM
I may be over simplifying the issue but if you want a 21 yard zero, zero the scope at 21 yards.  Then test fire it at a couple of other distances to get a feel for what it's doing.  If you're looking to adjust hold over or hold under by counting clicks, unless you have a REALLY good scope you will probably find that's an inexact method at best.  Repeatability on cheaper scopes may not be that good and movement for a given number of clicks may not be as expected.
Title: Re: Please help me calculate short-range adjustments !
Post by: Cableaddict on June 04, 2021, 10:59:37 PM
I'm not sure you're getting my point, Tom.

I need to make these calculations in order to decide which scope to buy.
Title: Re: Please help me calculate short-range adjustments !
Post by: mobilehomer on June 04, 2021, 11:01:31 PM
First, throw all the calculations in the trash. Forget twirling turrets. Do what Roadworthy suggested. Sight it in for 21 yards, then go shoot about 4 tins of pellets at different unknown ranges. This is the BEST way to learn and get better.

Get the 12 X 50. More light gathering. 4.1 mm exit pupil vs 3.2 mm exit pupil.
Title: Re: Please help me calculate short-range adjustments !
Post by: Cableaddict on June 04, 2021, 11:20:33 PM
First, throw all the calculations in the trash. Forget twirling turrets. Do what Roadworthy suggested. Sight it in for 21 yards .....


Once again:  There's nothing to sight in.  I haven't bought anything yet.     :(
Title: Re: Please help me calculate short-range adjustments !
Post by: mobilehomer on June 04, 2021, 11:42:36 PM
First, throw all the calculations in the trash. Forget twirling turrets. Do what Roadworthy suggested. Sight it in for 21 yards .....


Once again:  There's nothing to sight in.  I haven't bought anything yet.     :(


Read the rest of my post.
Title: Re: Please help me calculate short-range adjustments !
Post by: Cableaddict on June 05, 2021, 01:52:53 AM
Can someone help me figure this out?

I tried to figure holdover in mils, based on the online calculator's bullet drop figures at two distances.  However, again, it makes no sense that the physical bullet drop would be changing just because the scope height changes. There must be something wrong with that calculator.

Is there a verified way to calculate holdover / holdunder,  using inputted data?
Title: Re: Please help me calculate short-range adjustments !
Post by: JungleShooter on June 05, 2021, 03:49:35 AM
Cableaddict,

🔶  you'll need a proper ballistic calculator.
▪Strelok Pro (Android, iOS) ($8 for Pro, the free version is OK)
▪ChairGun Pro for Windows (free, at Hawke scopes website)
▪GPC ballistic suite (free) — this looks like the resurrected ChairGun Pro, but with full functionality on mobile devices, not just on desktops! 👍🏼
https://gpc.fotosoft.co.uk/Home.html


🔶 And you'll need to measure the expected scope height on your rifle, with the rings you're expecting to use.


🔶 Then get the specs of the pellet you're planning on using: weight, BC. Yeah, you'll need to know your gun's power.



🔶 Then do your calcuations:
Taking into account the size of the kill zone of your typical quarry:
Calculate the "optimum" (i.e., largest) point blank range (PBR) (say, from 14y to 28y) — this will also determine where your far zero will be.

The above ballistic calculators have a function to calculate your optimal (= "largest") PBR.


Now you can get your PBR closer to the shooter, but you will give up in PBR lenght (say, now it's from 11y to 22y).
➔ So, if you don't like the "optimum" PBR, play around with different zeros and look at the trajectory: how much the pellet is above or below the line of sight and at what ranges — and see what compromise you can live with. Find the best combination.



🔶 Then, do the same calculations for the other scope.
Compare the PBR of each, and how close the PBR is to the gun.
And make your decision....






Some other things to help you in your "quest": 👍🏼


🔶 Mounting the scope as low as possible allows the PBR to start closer to the gun.
For that, find the right size rings: The differences in actual height are different than what the manufacturer states (they just tell you: Height 1", 1.25", and 1.5" — but only the diagram will you what that means for your scope height).



🔶 I'm not sure I agree with the tradition to mount scopes high on bullpups.
And I'll share the arguments of my ignorance:
(1) For firearms their recoil is usually absorbed by putting the buttstock into the soft tissue of the shoulder.

(2) Holding the gun low (stock on soft tissue) requires a high scope, because the eye can't bend down that far.

(3) But airguns don't have appreciable recoil. Therefore, the buttstock does not need to be pressed into the soft tissue of the shoulder.
In other words, the gun does not have to be held low — requiring a high scope.

(4) The buttstock could go on any part of the shoulder, even on top of the shoulder (if you look at the curvatures of certain bullpups [EDgun, Taipan]) they are actually shaped for exactly that type of buttstock placement.
➔ I'll attach a diagram showing the difference of what I'm talking about.


Happy shooting and scope shopping!

Matthias

❌ Attachment: 
Bullpups:  Buttstock Shapes Determine Placement and Scope Height
Title: Re: Please help me calculate short-range adjustments !
Post by: rsterne on June 05, 2021, 12:34:10 PM
If your calculator asks for clicks/MOA and your scope is 42 clicks per revolution and 6 MOA per revolution, then the number you would input is 42/6 = 7 clicks per MOA.... Most scopes are 1/4" clicks at 100 yards, or if in Mils they are frequently 1/10th Mil clicks (about 3/8" at 100 yds)....

I'm not a turret twiddler, I figure the chances of it returning to zero are slim to none, so once I get my scope zeroed I don't touch it.... I base my far zero on what is required so that the pellet/slug doesn't rise out of my required kill zone, and that gives me a large point blank range for a dead-on hold that is typically 10-40 yards or further.... I then set up targets at 50, 75 and 100 yards and see where my POI ends up and make up a chart for THAT pellet or slug with THAT gun and scope.... and forget all about what the ballistics calculator says after that.... I just use the MilDots for holdover....

Bob
Title: Re: Please help me calculate short-range adjustments !
Post by: Yogi on June 05, 2021, 06:40:08 PM
I'm not sure you're getting my point, Tom.

I need to make these calculations in order to decide which scope to buy.

Unless your eyes are horrible, you would be much better off with open sights.  Much faster target acquisition, much.

If you got to buy one or the other, buy the 10X.  Scope reticles are set up at 10X and anything else you need to adjust.  And it seems adjusting is not your strong suite... :D
But get open sights! ;)

-Y
Title: Re: Please help me calculate short-range adjustments !
Post by: Cableaddict on June 05, 2021, 09:46:57 PM
If your calculator asks for clicks/MOA and your scope is 42 clicks per revolution and 6 MOA per revolution, then the number you would input is 42/6 = 7 clicks per MOA.... Most scopes are 1/4" clicks at 100 yards, or if in Mils they are frequently 1/10th Mil clicks (about 3/8" at 100 yds)....

Thanks !
Title: Re: Please help me calculate short-range adjustments !
Post by: Cableaddict on June 05, 2021, 09:47:54 PM
I'm not sure you're getting my point, Tom.

I need to make these calculations in order to decide which scope to buy.

Unless your eyes are horrible, you would be much better off with open sights.  Much faster target acquisition, much.

That was my original idea.  (A lot less money, too.)   Except I can't figure out how to mount the front iron sight down at the end of my barrel.
Title: Re: Please help me calculate short-range adjustments !
Post by: Cableaddict on June 05, 2021, 09:49:51 PM
Cableaddict,
 you'll need a proper ballistic calculator. .......

Thanks!  That's quite an effort.  I'll try to digest it all.

I didn't know Chairgun could run on a desktop. Everything today seems geared for tablets and smart phones.  (I feel so OLD........   lol.)
Title: Re: Please help me calculate short-range adjustments !
Post by: Cableaddict on June 06, 2021, 10:55:32 PM
If your calculator asks for clicks/MOA and your scope is 42 clicks per revolution and 6 MOA per revolution, then the number you would input is 42/6 = 7 clicks per MOA.... Most scopes are 1/4" clicks at 100 yards, or if in Mils they are frequently 1/10th Mil clicks (about 3/8" at 100 yds)....

Wait -  That didn't help at all.

As I wrote, those scope are 6 MILS per revolution, not 6 MOA.

So how do I calculate clicks per MOA? 
If it helps, on those SWAT scopes,  1 click is 1 cm @ 100 yards. 
Title: Re: Please help me calculate short-range adjustments !
Post by: Yogi on June 07, 2021, 01:07:02 AM
If your calculator asks for clicks/MOA and your scope is 42 clicks per revolution and 6 MOA per revolution, then the number you would input is 42/6 = 7 clicks per MOA.... Most scopes are 1/4" clicks at 100 yards, or if in Mils they are frequently 1/10th Mil clicks (about 3/8" at 100 yds)....

Wait -  That didn't help at all.

As I wrote, those scope are 6 MILS per revolution, not 6 MOA.

So how do I calculate clicks per MOA? 
If it helps, on those SWAT scopes,  1 click is 1 cm @ 100 yards.

So 10 clicks is one mil radian?  One Mil is 10 cm at 100 meters.  This is true only at 10X on a sfp scope.  Does not matter on FFP scopes or fixed scopes.

-Y
Title: Re: Please help me calculate short-range adjustments !
Post by: JungleShooter on June 07, 2021, 01:20:16 AM
If your calculator asks for clicks/MOA and your scope is 42 clicks per revolution and 6 MOA per revolution, then the number you would input is 42/6 = 7 clicks per MOA.... Most scopes are 1/4" clicks at 100 yards, or if in Mils they are frequently 1/10th Mil clicks (about 3/8" at 100 yds)....

Wait -  That didn't help at all.

As I wrote, those scope are 6 MILS per revolution, not 6 MOA.

So how do I calculate clicks per MOA? 
If it helps, on those SWAT scopes,  1 click is 1 cm @ 100 yards.

🔶 I'm not sure why you would want to convert to MOA.
The MTC Prismatic scopes have turrets and reticle both in MIL.

There are plenty of trustworthy ballistic calculators that are a little more global minded that will give you the choice of either MOA or MIL.
❌ If you or anyone else would like a walk-through of how to set up either Strelok Pro or GPC Ballistics Applications and how to use it, send me a PM. I'll send you a Zoom link for a video conference.



🔶 One turret revolution on either scope changes the POI by 4.2 MIL, by doing 42 clicks once around. 

Holdover shooters could care less, sure, but that uneven random number in itself is a sin against any self-respecting scope turret dialer.  >:(
(There are very few scope engineers who have committed this captial offense — the Optisan EVX 4-16x44 comes to mind [4.8 MIL/revolution].)



🔶 Just looking at some photos of the Hatsan Flashpup — you are out of luck — the scope rail is mounted somewhere between the Empire State Building and the Sears Tower. Way high.
Well, you got a whole slate of other options how to work around that and still shoot those critters that are so close you can see the white of their eyes. 💀


Matthias 👍🏼😊
Title: Re: Please help me calculate short-range adjustments !
Post by: Cableaddict on June 07, 2021, 02:10:10 AM
🔶 I'm not sure why you would want to convert to MOA.

Because the calculator I've been using takes that as a parameter,  not click-per-mil.

I downloaded that GPC app suite you told me about, just haven't had time to look at all the options & figure out how calculate holdover.

Any chance you had time to run it in Strelok?

----------------

Oh,  FWIW,  I figured out an easy way to lower my picatinny rail by about 1/8",  so the new bore-to-scope numbers would be  ~ 2 7/8"   and 3 1/8"

If I don't need the MTC mount's angle adjustment, I could hopefully use aftermarket medium high mounts, and get the SWAT scope lower. - But I can't plan on that just yet.
Title: Re: Please help me calculate short-range adjustments !
Post by: Motorhead on June 07, 2021, 02:27:06 AM
LOL .... geez just take the K.I.S.S. route !!!!

Zero your POA and POI at at 28-30 yards.   DONE !!!!  leave turrets alone !!!

Take a sheet of paper and draw a couple side to side lines on it.  Confirm your zero range hits on the line, Perfect now proceed.

Using the scopes paralax or a tape measure or any way to give you the distance to target .... CHANGE YOUR DISTANCE to target and note what it is ?  SHOOT THE LINE again and NOTE WHERE pellet strikes in relation to line ? BEING CLOSER you will hit lower than the line, using scaling on scopes reticle make note how LOW it hit / THAT IS YOUR HOLD OVER for that range.  Change distance in closer and closer doing the same.  Inverting your measured drop below the line to a hold over value.

 easy peezy !!!  all you need to do is refocus your parrilax for a clear view in scope, note distance and hold over the required amount.  No clicking or screwing with turrets !!!!
Title: Re: Please help me calculate short-range adjustments !
Post by: JungleShooter on June 07, 2021, 12:14:16 PM
Motorhead, 😊

the OP doesn't have the scope in hand to do run your shot test — he's trying to decide which of the MTC Prismatic models he should get.
And after this post he might decide to do something totally different.... 🤔




Any chance you had time to run it in Strelok?

➔ Yes, I did. In your other thread, here:
https://www.gatewaytoairguns.org/GTA/index.php?topic=188003.msg156163549#msg156163549 (https://www.gatewaytoairguns.org/GTA/index.php?topic=188003.msg156163549#msg156163549)

And I couldn't get much better numbers for you than those that you already know.

➔ Your scope is just way too high for a point blank range (PBR) starting at 6 yards.
➔ And quite frankly, your desired PBR starting at 6y is just not realistic with normal optical tube-type scopes and normal scope mounts.
I'M SORRY!!  😟😟 


🔶A per your specs, your 36gr slug with a 0.1BC with at 900fps MV — and assuming a killzone of 1" — would need a scope centerline at least as close as 1" to the barrel centerline, for your mentioned 21y zero. Well, that's just not going to happen with regular scopes and mounts. 😟 

🔶You could zero at 10y, and then you can get away with about 1.5" scope height, and still can hold directly onto your quarry's 1" killzone at 6y. But your point blank range (PBR) ends at 14y. Anything farther will require holdovers or clicks.

🔶A scope height of 1.5" — maybe there are some scopes out there that have a 1" tube and both an objective bell and an ocular that are 1" (24mm) or less....  :-\   But your MTC Prismatics have the exact opposite, cf. below....





If I don't need the MTC mount's angle adjustment, I could hopefully use aftermarket medium high mounts, and get the SWAT scope lower. - But I can't plan on that just yet.

I'm sorry to say that your MTC Primatics have huge honking tubes:
10x30:  34mm tube.

12x50:  42mm tube. Good luck finding scope rings for that.... Prices will be through the roof.





Oh,  FWIW,  I figured out an easy way to lower my picatinny rail by about 1/8", so the new bore-to-scope numbers would be  ~2 7/8"   and 3 1/8"


Running the numbers for a 2⅞" scope height — and a 1" kill zone:
ZERO   PBR     
10y       8-12y
13y     10-16y
15y     12-18y




❌ Cableaddict, I appreciate what you're trying to do. 
 
Sometimes physics gets in the way of what we're trying to do....  >:(    And I don't appreciate that.

But without physics we wouldn't be shooting, we wouldn't even be able to discuss this topic.... 😄


As with many issues in shooting (and life) — list your priorities and search your soul for which priorities you are willing to make a compromise, and which ones are the deal breakers.




🔶 Some final thoughts: 🔶 

🔶(1) 
Your extreme short ranges are extreme. ➔ Can you get farther away from your quarry, say 10y? ➔ If you want to use a regular scope, you could probably get away with a minimum parallax of 10y — if you dial the magnification low (say 2x, 3x, or 4x). It also helps if the scope has a small objective diameter (say 32mm, 24mm, 40mm — and not 50mm).
Or you get one with a shorter minimum parallax: The UTG bug busters have a min. parallax of 6y. The SWFA 3-15x42 FFP has 7y (but price around $600). 


🔶(2)
Using two different sights would make things a lot easier. For extreme close ranges: A laser ($50) or a red dot ($100), side mounted ($30). And a regular scope for "regular" ranges — now you have a much larger selection, better prices, without the constraints of a 6 yard PBR.


🔶(3)
We're all enabler at GTA, so... — Just get a second gun! A multishot Artemis PP750 in .177, with open sights, for your extreme close range shots.
Tell  your significant other: "I had to buy it — I didn't want to — but physics made me do it."


Matthias
Title: Re: Please help me calculate short-range adjustments !
Post by: Cableaddict on June 07, 2021, 02:39:30 PM
"physics made me do it! "

LOL.  that might just be my new motto.  Gotta' get some tee shirts printed up.    :D


Mathias, I can't thank you enough for all that work & the thoughts you put into this.  It's also good to know that I wasn't far off with my own calculations.

As for my 6 yard kill zone, that's cast in stone, unless I move to another house.  It's the only area I have where I can be completely hidden from the neighbors.

---------------------------

So here's a different question:

Assuming I have to mount an offset red dot of some kind (which one, I have no idea)   in your opinion, will it matter much if I go with the 12x50 instead of the 10x30?    They both have the same (very wide) FOV, so the 12X seems like a better choice to me, except for the height issue.
Title: Re: Please help me calculate short-range adjustments !
Post by: Motorhead on June 07, 2021, 03:54:15 PM
Shooting THAT CLOSE ... variable power with 2 or 3X on the low end.  Mil dot reticle most useful and speedy
Title: Re: Please help me calculate short-range adjustments !
Post by: Bayman on June 07, 2021, 06:56:12 PM
Six to twenty one yards??? Open sights at that range is best. Peep sights if you vision doesn't work well with buckhorns.

I have a small yard and pest at similar distances. I've botched more shots with scoped rifles than my peep sighted guns. My scopes are mounted half as high as yours and the hold under hold over is problematic. With 3 inches over the barrel you're going to have real problems calculating hold over/under. With my peeps it's point and shoot from 5 yards to the back fence at 20 yards.

High magnification scopes are just terrible for close work. Straight 4 power or 2-7 is more than enough to 30-35 yards depending on the size of the target. Plus mounting them that high compounds the problem. I know this is not the advice you looking for but you're building the wrong tool for the job.
Title: Re: Please help me calculate short-range adjustments !
Post by: JungleShooter on June 07, 2021, 07:32:10 PM
+1

Yupp, the previous posters already said it: ✔️ 

10x (or 12x) is waaay too much magnification for 6y.
Because the field of view at that magnification is very narrow ➔ so you'll have a hard time finding your quarry, and if the quarry doesn't sit still, so much the worse.


I'll attach a Scope Specs Table for variable magnification scopes that are 3-9x and 3-12x — and depending on what your farthest ranges are, you could go even lower to a 2-7x / 2-6x (the 1x scopes tend to get expensive). 😊

Matthias

❌ Attachment:Scope Specs Table 3-12x/ 3-9x/ and short scopes
Title: Re: Please help me calculate short-range adjustments !
Post by: Cableaddict on June 07, 2021, 07:58:47 PM
High magnification scopes are just terrible for close work. Straight 4 power or 2-7 is more than enough to 30-35 yards depending on the size of the target. 

I hear everything else you're saying, but I disagree strongly with this.

Because I'm planning on getting an MTC SWAT, I've been using my Bugbuster always at 9x power, to see if I could get used to it.    Using lots of turret adjustment and shims, I can get it zero'd at 6 yards.   In use,  I find it just fine at 6 yards.  - especially as I've gotten used to shooting with both eyes open. 
For more "mobile" hunting,  the SWAT scopes have a MUCH wider FOV than standard designs,  (33' @ 100 yards)  and so the typical disadvantage of high power is just not there.

And at 30-50 yards, 9X is barely enough for my 63 y-o eyes to guarantee a head or heart shot on some small critter.

Another advantage:  Higher power scopes, if well-calibrated, can serve as a poor man's rangefinder, due to the reach and the short DOF.  These two MTC scopes are reportedly extra good in this regard.

One final advantage:  When I'm hunting, I like to look through the scope as if it were binoculars, and enjoy seeing the other wildlife.  When there's no legal game around, this makes for a peaceful interlude.  For that, the more magnification the better, esp with the extra FOV these scopes provide.
----------------------------

I don't know why these scope aren't more popular with small game hunters. IMO it's the perfect design, except for the height of the MTC mounts.
Title: Re: Please help me calculate short-range adjustments !
Post by: Bayman on June 07, 2021, 09:32:50 PM
My apologies I wasn't aware of the MTC SWAT design characteristics until I read this post and looked them up. The concept looks good.

With it mounted that high the hold over/under calculations are going to be a real bear at close ranges. Probability better off with a standard 30 yard zero and mostly deal with hold over at near and far.

With my guns zeroed at ten yards in my basement, at 5 yards I have around 3/4" to 1" hold over, and at the back fence (20 yards) it's about that of hold under. It's a pain in the butt when you're trying to head shoot a busy squirrel with a kill zone that's only 1/2" in diameter. It's very easy to miss the mark with a scoped gun and have a wounded animal running off in a neighbors yard.
Using my own advice it'd be better for me to zero the guns further away so I only have hold over to deal with. Unfortunately most of the time they're sighted in for the ten yard basement range. With peeps there's no appreciable difference between 5 and 20 yards. It's point and shoot. Past 20 yards outside my yard in the field or woods it's a scoped gun every time. Even then targets sometimes pop up close and the scope becomes a liability.
Title: Re: Please help me calculate short-range adjustments !
Post by: Cableaddict on June 07, 2021, 09:43:35 PM
Past 20 yards outside my yard in the field or woods it's a scoped gun every time. Even then targets sometimes pop up close and the scope becomes a liability.

Yes, exactly.  That's why this is making me nuts.  (Although, again, using an offset red dot will likely be the answer)

With my bugbuster, I can easily adjust the turrets for a 6 yard zero,   but then even at 20 yards it has to be set back.  a LOT.     There's no way to hunt like that and be able to hit both close and far. 

Sadly, I REALLY don't want to own two rifles. - Mostly because of what I wrote about watching the non-game wildlife through the scope.  I'd want that 12x50 SWAT on my yard rifle, so as to watch the song birds up close.  I like to do that while having my morning coffee.  (and waiting for any HOS, Starlings, or blackbirds to show their obnoxious little faces.)

-------------------------

BTW-  is 30 yards really considered the "standard" for small game pcp hunting?    If I can find a decent, cheap red dot reflex, maybe I'll get the big SWAT and set it there.
Title: Re: Please help me calculate short-range adjustments !
Post by: Bayman on June 07, 2021, 09:54:32 PM
I'm not into pcps, but most airguns (and rimfires) shouldn't be "climbing anymore after 30 yards. This is provided your using average height mounts.

So there is no actual standard zero distance but this is about the distance that you'll probably only have one zero so every in front and behind is hold over.
Title: Re: Please help me calculate short-range adjustments !
Post by: JungleShooter on June 07, 2021, 10:03:25 PM
🔶 OK, Allen, you are onto something there! 🔶

The reason I buy scopes with variable magnification is because I need a wide field of view (FoV) for close range shots and moving quarry.
And I also want a high magnification for those longer shots and for target shooting.


So, FIRST I look at the FoV at the bottom end of the magnification (which is the harder one to get). There I'm looking for about a 30-35ft FoV at 100y.
23-29ft is margnial, but OK.
36-41ft is excellent.


SECOND, I look at how much magnification I need for my long shots, maybe 12x, maybe 18x, maybe 24x, just depends on the shooting scenarios.


Then I look at the scope specs and see which scopes qualify.



Now, Allen, your MTC Prismatic throws this whole process under the bus (or in the gutter). 😄 In a good way!

Because these prismatic scopes do NOT have variable magnification. But they still have a very wide FoV. At the same time! 😄


▪MTC Prismatic Atom 10x30
32ft @ 100y

▪MTC Prismatic 12x50
30ft @ 100y


And because these are fixed magnification — the reticle will be calibrated always correctly (unlike SFP scopes that have different subtension at every magnification)!
Very cool! 👍🏼


▪Turrets = MILReticle (SCB2) = MIL

▪The turrets are lockable.
▪Yeah, 4.2mil per revolution makes no sense.
▪Max. elevation adjustment is 17mil = 60moa
▪Side parallax down to 7y.
▪Illuminated reticle (brightness and on-off separately)  ▪Comes with elevation adjustable mounts.

Size: 10x30 
4.8" = 12.3cm short
10.6oz = 300g

Size: 12x50
6.1" = 15.6cm short 
16.2oz = 460g


Thanks, Allen, this is something I totally missed. 👍🏼

Matthias
Title: Re: Please help me calculate short-range adjustments !
Post by: Cableaddict on June 07, 2021, 10:13:23 PM
^  I knew you'd come around!  lol....


BTW, the 12x50 has a FOV of 32.8',  not 30'.     

The only downside to these would be if someone just hates the short (zero) eye relief.   Personally, I consider that to be yet another great feature, as it speeds target aquisition.

Oh, and since you mount these farther back on the rifle, it also means even less weight being supported by your forward arm.

win-win-win.   ;)

---------------------------------



But I still don't know which one to get.  I want that 12x50 BADLY,  but besides the extra 1/4" height, it also has a shorter FOV, and so will require more field adjustments as critters dart out from wherever they might be.   (I have this dream of taking out a Ruffed Grouse in flight, with a .25 slug.  I know it will never actually happen, but one must have goals!  lol....   )
Title: Re: Please help me calculate short-range adjustments !
Post by: JungleShooter on June 10, 2021, 03:42:27 AM
Allan,

let me complicate life and scope shopping for you (and maybe a lot of other shooters), OK?  🤣 


🔶 Again, the marvel of these prismatic scopes is this: 
A 10x scope, but with the FoV of a 3x scope.

And this is how it looks in practice:
● I follow the aim-small-miss-small adage by using 10x magnification — but at the same time with a FoV of "a typical 3x"
—I keep the rapidly moving quarry in the scope,
—I see the effects of wind on grass and wind flags,
—I watch for other quarry, 
etc.



🔶 Now, I have found a whole slew of these cool aiming machines heading our way....
The brand name is Immersive Optics, and they seem to be the same manufacturer that makes the MTC SWAT Prismatic scopes.
The initial info I got from here:
https://www.airgunnation.com/topic/immersive-optics/ (https://www.airgunnation.com/topic/immersive-optics/)


Steve from Airgunology explains on that thread:"Immersive Optics is a new brand of scopes from the same designer as other "popular" scopes you may know of.
These are models that were not taken up by the major boys [like MTC?] and so are being released by the designer under the Immersive Optics brand.
I am a reseller of them in the UK, but unfortunately, due to costs and warranty costs, I will not ship outside Europe.
I believe that there will be a USA reseller coming online very soon."


Here are the specs of the Immersive Optics prismatic scopes (note that they have capped turrets and an even 5 mil per revolution, not the funky uneven number of MTC):

(http://airgunnationforum.s3.us-east-2.amazonaws.com/Scopes.%20Immersive%20Optics.%20Prismatic%20Scopes.%20Specs.%202021.1623306090.jpg)



Some seller in the UK might be shipping to the US already, just haven't searched enough yet.


BTW:   MTC wrote back and told me the SWAT 12x50 has a 30ft FoV @ 100y. 


I'm excited about these new options! 😄

Matthias
Title: Re: Please help me calculate short-range adjustments !
Post by: Cableaddict on June 10, 2021, 03:46:48 AM
Wow,  interesting!

Of course, there's no guarantee these will be of good quality, but I'm in no rush.

The best thing I see is that they have a 10x40.      ;D   ;D   ;D   ;D     

Oh yes.


BTW:   MTC wrote back and told me the SWAT 12x50 has a 30ft FoV @ 100y. 

Hmm.  Well then their own website is wrong, as it says 10 meters.

I wouldn't put too much stock in the MTC techs, BTW.  I had about FIVE back & forth emails with them, just trying to get the bore-to-element height, and they literally never gave me an answer.   Luckily, Airguns of Arizona has both in stock, and salesman Chris was nice enough to meaasure them for me.
Title: Re: Please help me calculate short-range adjustments !
Post by: rsterne on June 10, 2021, 12:59:55 PM
30' field of view at 100 yards is 3' at 10, and less than 2' at 6 yds.... I find that nearly impossible to use, particularly in low light / low contrast situations.... Give me a low power with a much wider field of view (and usually brighter) for close in, please.... As far as holdover vs. turret twiddling, if you have to switch from a close shot to a far one, once again MilDots are the way to go.... It's a LOT faster, and I have never had such a close shot that I couldn't use the dots, even with a Bug-Buster shooting grasshoppers at 2 yards.... Sighted at 20 yards, I can use 5 dots of holdover at 2 yards and it's dead on.... SPLAT!....

Bob