Flatness of trajectory

[Dave King]

Newbie_71

I'll run the same sample info as I did for the 308 for the .223 Rem with the 52 MK at 3240. (About 500 yards out and the slower 308 Win wins in the Danger Space arena.)


223 round at 3240fps, 52 (.225 BC) @ STP. Use a 12 inch kill zone size (two dimensional target) and we have a continuous danger space (MPBR) of 365 yards with a 315 yard zero. (Pretty good so far.) BUT move that critter to 500 yards and you now have a danger space 46 yards deep (474 to 520). Now well head out to 650 yards (my max range) and the danger space is down to 24 yards deep (638 to 662). 1000 yards and we'll have just under 10 yards of danger space (995 to 1005) (for comparison a military sniper would have about 24 yards of danger space for a 36" torso hit).

 

[Brent]

Worth noting -

The "new" Exbal PDA program gives you an option to input the target height in the Ballistic Retical Analysis screen and then will calculate the near and far range in yards that each Tic mark on your specific reticle is actually zeroed for.

The older Exbal program will tell you how many inches high or low you would be if using each of the Tic marks based on the target distance you enter... I actually prefer this way of looking at the solution myself, although as pointed out, the other has its inherant advantage as well.

If you're a little bit limited on elevation dialing, or just prefer to use an R2 reticle or other BDC type reticle, and knowing you've got to dial some oddball number like 20.88 MOA to hold on a target at 1048 yards is made much easier than holding the 20 MOA Tic mark .38 over POA if you instantly know the POI will be just about 8" low if holding right on the Tic itself... Not hard to hold 8" high and just use the 20 MOA Tic mark now. On the other hand, if you think holding on a Tic mark that's kind of close, but not nearly perfect and it may be too far off, then punch it up and see it only amounts to and inch or two at what ever range, that's what I also find very useful about it.

Nice to see on the new program how far off you can be in yards though and still keep the shot within so many predetermined inches of POA (with a rig that shoots one holers that is), especially if you're ranging a bush, rock, or what have you that's just close to the animal or path/area one might show up at.

I'll stick with a high BC bullet myself, I need all the help with cheatin wind way out there that I can get, up closer I'm less concerned with as my rangfinder is spot on and work well all the time... out far's where I run into the major error stacking and wind issues.

My wife seems to think the "Danger Space" is still much, much, too big, at any range, as I still can't convince her to set up a chair and hang out next to my target to relay back to me each POI via walki-talki!