Trail NP 80 yard group and Chairgun Question

[cheerIO]

Well, this is my second Trail NP AW. Although a little inconsistent at times, this one seems to be shooting about a thousand times better than the first one.

I shot this 3 3/4" group rested at 80 yards. I'm pretty happy with it. It was pretty blustery today and I was really stoked to just be hitting the target. I have never shot an airgun this far before. Then the wind all of a sudden stopped and I nailed the last three right in a line off the bull. Those last three were a 3/4" group. 

I'm using ChairGun mobile on my iPhone but it was just not giving me the right hold overs for what I was shooting at. I'm using a CenterPoint 4x16x40 scope at 9x magnification.

FTT's
735 muzzle velocity
1.25 in scope height
15 yard zero
4.000 clicks MOA
9x Cal mag
9x mag

ChairGun is telling me to hold over -5.9 dots at 80 yards. I was only holding over -4.5 to shoot this target. I can't figure out what I have entered wrong. The only thing I am not sure of is the "cal mag" I read the "help document" and I still don't really understand what that setting is and why they have "cal mag" and "mag". So I just ended up putting 9x in both slots. Is this correct?

Anyway. It was a rush to hit what I was aiming at that far away. This week I'll try for a 100 yard group. 

[clashley]

cant help ya with the program but thats pretty good i think for 80 yards

[Bryan Heimann]

Nice shooting!  Might be getting a better BC from your barrel, or might be achieving a higher velocity than you thought (if it's been chronied, perhaps it is shooting faster after breaking in a little as well).  I might be wrong, too.

[cheerIO]

Well I don't know where I got the 735 muzzle velocity. Wishful thinking on my part I guess. 
I just re-chronied it and I got an average of 729.25
But my extreme spread was 12.7 and standard deviation was 4.13
Those are a lot tighter numbers than I was ever getting before.

ChairGun had the weight of the FTT's down as 14.8, my tin says they are 14.66 so I changed that and with my new muzzle velocity all it did was add another -0.1 to my hold over. Now it says 6 dots at 80 yards. Oh well. 

Thanks for the compliments. I don't know how other people shoot, but I was pretty proud to be nailing the target at that range. 

[Bryan Heimann]

I suppose it'sdue to either how tight thechoke is, or the twist rate, maybe both- but some barrels will yield a better BCwith a given pellet than others.

Edit- one other factor is whether the gunvwas zeroed off-hand or rested.  My guns seem to have more of a "bounce" to them when shooting rested vs. off-hand.  Doesn't make much difference untill i stretch it out to 35 yards or so, where i begin noticing the higher impact of the pellets...

[PaperPunch1]

cheerIO,
Are you sure of the 1.25" scope height? (many work out to be 1.5")
Secondly, the chairgun programs "generic mil-dot" isn't as generic as it could be.....in that I mean the centerpoint reticles won't work exactly with the program.
This may be the best time to buy a hawke scope.....then you'd be GOLDEN!!!!!
What I did for 80 yards was look at the chart to the left of the graph, and see the "inches low" for 80yds. (mine says 13.5") so I took a 13.5" cardboard strip out to 80yds, and set it up.
Then I benched the rifle and looked to see how many mil-dots high the cardboard was, from the crosshairs to the bottom of the target.  I use the closest dot to figure holdover for that shot. If it's between dots I just fudge it a bit.
PaperPunch1

[Scotchmo]

The scope height does look a little low. It should be measured from scope center line to bore center line. But that is not your main problem:

A standard mil-dot is calibrated at 10x. Most scopes of 12x power and less use standard mil-dots. Many of the higher power scopes use 12x as the calibration magnification. That is probably what your Centerpoint uses. I have never seen a 9x calibration.

5.9 x 9x/12x = 4.43

4.43 is close to the 4.5 that you are getting in the field. Enter the corrected scope height if needed and change the Cal mag to 12x and you should be good to go.

The Cal mag box contains the constant for your scope. The Mag box can be set to whatever you have the magnification ring set to on your eyepiece.

[cheerIO]

Thanks for all the help guys.

My scope height was low. I measured it to be about 1.75"

Scotchmo, thanks a tonne. Changing the Cal Mag setting did seem to bring the numbers into what I am seeing. I will try some different ranges with the new settings this week and see how it goes.

And I may look into buying a quality scope. I really want to make a decent 100 yard group. I have distances already marked out in 15 yard increments. But I've run out of mil dots on this CenterPoint. It only has four dots in the center and the rest of the reticle is a solid line. 

Chair gun says my hold over for 100 yds would be -6.2 dots. I guess for the moment I could try sighting in 2 dots high at 15 yards and then use the full scale at 100 yds. Is that doable? Would the scope even adjust that much?

Thanks again for help.

[Scotchmo]

Many of the new Leapers and Centerpoint scopes have 9 dots in each quadrant. That is how my Leapers 3-12x44 SWAT Compact is.

[skid9832004]

zero at the most top mill dot then you will have many mills of drop many snipers use this for the extra elevation and simple ease of holds its called the poor man horus.

[z28rod]

These rifles can be very very accurate...

[lillysdad621]

the generic mil dot setting on CGP will work with any scope that has the reticle on the prime focal point. It does not matter the make as the distance between dots (brackets) will increase with the diminishing magnification (that is why you may use aiming points at different magnifications to get chosen target distance aim points. And you are correct about the bracketing used on mil dots at 10X. that is the standard for accurate rangefinding as long as you know the average height of a target. Even people who discount the duplex (30/30) reticle as "not very precise" could benefit from learning how to use it. It brackets 30 inches at 100 yards at 4x from the top thick to the bottom thick. or with quick math you can tell that the distance between the x and the bottom thick at 50 yards is 7.5 inches... or at 8x is only 3.5 inches... So you can use a 30/30 for precise shooting as long as you know the drop of your pellet pass your zero. If you are going to get a hawke, play with the SR series...