4dof and bullet flight off and I am not sure why.

[ssteve]

So my local range only goes to 300 and normally most calculators I have used are spot on with little to no adjustment. Recently switched to copper projectiles and currently testing both Hornady gmx and Barnes ttsx. Both shoot great with 43.8 grains of h4350an both are zero’ed at 100 with no difference between the two even though there is about 40-50fps difference between the two.

Barnes is coming out at 2955 according to my Magnetospeed and gmx are at about 2900.

rifle is a bergara hmr in 6.5cm with about 800 ow the pipe. Easy 3/4 Mona or better gun with both projectiles At 100.

Info into 4dof is:
2910, sea level, 29.92, 60deg, 50%
sight height 1.8, axial rom factor 1.0, angle 2*

info to dial to 300 yards is 1.04 Mils Using the 120 led-m 4dof and 1.09 Mils using the .450 g1 b.c in the basic calculator. dialing 1 mil hits are 2.25” high of poa. So roughly .25 Mils high at only 300.

With the Barnes ttsx most things are the same but I am using the basic calculator in the Hornady app since they dont have data in 4dof on this bullet. Info into the calculator is 2960 and a b.c. Of .412 from Barnes which I assume is a G1 number. Both Hornady and KAC bulletflight put my dial up at 1.1 Mils to 300 yards with a 100 yard zero. If I switch to g7 it drops to .89 Mils. I only had ten rounds and messed up with my first shot and left my elevation set at zero so I just shot a group using the same poa. group was about 8” low. Dialed up to 1 mil and the group was 2.5” high.


So to sum up both caclulators want about 1.1 dialed up and the gun is shooting about .80 Mils.

Loading some more of both up now and plan to go out to some Blum land and try and get out to 600-800 hopefully Wondering what I should be looking for in my data to tue it up?

 

[isofahunter]

Adjust axial form factor so correction produced is what happens on paper. If you adjust to .95 what is correction produced? If you cannot get it to line up with that adjustment you have an error in your input.

 

[Long Range 338]

You have to verify everything and I mean EVERYTHING (velocity, environmental info, distance to targets, etc.) also do not discount the need to verify your scope is adjusting the actual amount dialed. Without doing all of this first you run the high possibility of building error into your system. You shouldn't be seeing more than .1 mil from what is predicted/actual at 300 yards. You need to get to 600-800 to actually start doing your truing. At 300, just document and move on.

 

[ssteve]

Copy that. Going out tomorrow and I’ll true at 300. Just finished making a tall target to test the optic.

 

[isofahunter]

Have you watched the 4 dof video?

 

[ssteve]

Yeah but the problem is there’s no axial form factor unless your using a bullet in their library.

 

[ssteve]

So I wasn’t able to setup a target but there’s a beat up 12x18 steel plate on the hillside where I was hiking and I was able to get some rounds on it. Used the same calculator for both the gmx and the ttsx and shot at 465 yards and 677 yards. Calculator put 465 at 1.89 Mils, I dialed 1.8 and hit 10 out of 10. At 677 calculator gave me 3.72, I dialed 3.6 and hit 9 out of 10 with elevation good on the miss it was just off edge from windage. I’ll go back to the range next week and tall target test the optic but I feel like its tracking pretty well. I was able to get multiple first round hits on a soda can, and a couple clay pigeons at over 500. All the data the calculator gives me I am just rounding down on which leads me to think that maybe my zero is high?