Re: Not sure my PST is tracking right
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: DernHumpus</div><div class="ubbcode-body">I have a 2.5-10x mil/mil PST on a R700 SPSTactical. It is zerod at 50 yards and the scope height is 2.1 inches.
I shot today at 650 yards and had to go up 5 mils. This is not correct from any of the ballistic tables I have found. I had some 168 smks and 175 smks loaded up and both were impacting at about the same height at this distance.
If I do a box test at 100 yards, each mil should be 3.375 inches apart? </div></div>
Hmmm, what do you mean exactly by "this is not correct form any of the ballistics tables I have found"? Are you just looking at ballistics tables with those rounds, and trying to say that you should have a certain amount of drop, or did you actually run the numbers for your own load? You mention you had some rounds loaded up, which might suggest handloads. So have you chronographed how fast these rounds are actually going, or are you just taking a S.W.A.G at their velocity? The velocity of the load makes a big difference. I mean you're shooting a rifle with a 20" barrel, so you may be losing a bit of velocity there. Then I don't know what kind of temperatures and elevation you're shooting in. At this time of year, it's quite probable that you're shooting in colder temperature than standard conditions, so you'll have some difference there. Then there's a chance that you aren't getting the velocity that the tables are using, or that you have a temperature sensitive powder and it's not putting out the velocity in colder temps.
Part of the other problem is that you're using a 50 yard zero. Do you have a particular reason that you zeroed at that yardage? Most of the tables that you're looking at probably have 100 yard zeroes or further. This will also have an effect.I just quickly threw together some quick numbers for normal loads using a .308 and the 168 or 175 SMK, at standard temp and pressure, running those bullets around 2,550-2,600 fps, I was getting something like 4.1-4.3 mils at 650 yards with a 50 yards zero. If you weren't quite pushing that kind of velocity, had different temps, or air density values, I can see how you could easily get in the neighborhood of around 5 mils.
So the question again, did you just look up some tables, or did you run the ACTUAL numbers for your load and see what they should be.
