Ballistics
- Thread starter madluk18
- Start date
sir_springer
Regular
- Location
- East Kootenays
Also www.gunsim.com
alright, now i was wondering if someone could explain this to me.
at 25yrds all of my shots touch or are very close to touching.
now i've been told 0 at 25 is 0 at 200. which has some truth to it,
yesterday I went out and shot my 6.5x55. used Barnes 120gr TTSX with 43.7 grains of RL22.
like i said I was bang on at 25 yrds. moved to 100 yrds. i was at least 7-8 inches high and off to the left about 4 inches, I put 6 rounds on this paper. and it was all the same. way high and to the left. I moved to 200yrds. and i put 3 rounds into it. two were high one inch and to the left 2 and 4 inches. and the last one was centered and 7 inches high.
I was wondering if someone could explain to me what I'm doing wrong?
at 25yrds all of my shots touch or are very close to touching.
now i've been told 0 at 25 is 0 at 200. which has some truth to it,
yesterday I went out and shot my 6.5x55. used Barnes 120gr TTSX with 43.7 grains of RL22.
like i said I was bang on at 25 yrds. moved to 100 yrds. i was at least 7-8 inches high and off to the left about 4 inches, I put 6 rounds on this paper. and it was all the same. way high and to the left. I moved to 200yrds. and i put 3 rounds into it. two were high one inch and to the left 2 and 4 inches. and the last one was centered and 7 inches high.
I was wondering if someone could explain to me what I'm doing wrong?
sir_springer
Regular
- Location
- East Kootenays
I'll do a couple groups at 25 yds to get on paper and save ammo, then move out to 100...even if I've first bore-sighted the rifle.
1" at 25 yds equals 4" at 100, and 8" at 200. So one does not have to be very much off of dead center at 25 yds to see groups land 4" to 8" off of center at 100 to 200 yds. And what appears to be a wonderfully tight cloverleaf group at 25 yds can turn into a 2" to 4" group at 100.
I wouldn't pay much attention to this seemingly big difference between the two ranges. Once generally on center at 25 yds, move out to 100 yds and begin the real process of sight in there.
One thing to note, just in passing, no idea if this applies or not...
If using rear windage adjustable dovetail rings and bases, moving the rear rings east/west to save on internal adjustments of the scope, while a good idea, is almost certainly going to cause torquing of the scope tube, which, if severe enough, can mess up internal workings, or even actually put a permanent bend in the scope that can only be repaired by the factory. The front rings are far too tightly twisted and locked into the front base to compensate. This is precisely why I only use Burris Signature rings, as I can loosen the front rings a tad and allow the scope to pivot within the plastic bearings as I move the rear rings, and then re-tighten for the next group.
1" at 25 yds equals 4" at 100, and 8" at 200. So one does not have to be very much off of dead center at 25 yds to see groups land 4" to 8" off of center at 100 to 200 yds. And what appears to be a wonderfully tight cloverleaf group at 25 yds can turn into a 2" to 4" group at 100.
I wouldn't pay much attention to this seemingly big difference between the two ranges. Once generally on center at 25 yds, move out to 100 yds and begin the real process of sight in there.
One thing to note, just in passing, no idea if this applies or not...
If using rear windage adjustable dovetail rings and bases, moving the rear rings east/west to save on internal adjustments of the scope, while a good idea, is almost certainly going to cause torquing of the scope tube, which, if severe enough, can mess up internal workings, or even actually put a permanent bend in the scope that can only be repaired by the factory. The front rings are far too tightly twisted and locked into the front base to compensate. This is precisely why I only use Burris Signature rings, as I can loosen the front rings a tad and allow the scope to pivot within the plastic bearings as I move the rear rings, and then re-tighten for the next group.
You are doing nothing wrong and in fact you are doing what everyone should do, actually shooting at the distances you would expect to encounter while hunting.
Ballistic charts hold very little meaning in the real world as you have found out.
Sight the rifle in at 100 yds 2-3'' high only use 25 yds to get on paper. this should zero at 225-250 yds but it is only math you should shoot your rifle at 200yids to make sure, ballistics are only mathematical calculations .
Tight groups at 25yds can certainly open up when you get to 200yds. An adjustment of 4 clicks at 25 yds will barely move the point of impact, but at 200 yds will be off by 2 inches. Sight it in where 90% of your shots will be, and compensate for the other 10% when the time comes...
The most important thing is that you are out practicing, and getting to know your rifle and load.
The most important thing is that you are out practicing, and getting to know your rifle and load.
The 25yd / 200yd thing depends on your load, bullet and how high your sights are above the bore. Especially how high the sights are. I would agree with struff55 that 3" high at 100yds will zero somewhere around 225yds, that is around what I found on my 6.5x55 last year. Hot loads with a good bullet will zero on the farther end of that, softer loads with an average bullet will zero a bit over 200yds.
I use the JBM or Big Game Info ballistic calculators to get trajectory charts.
JBM - http://www.jbmballistics.com/ballistics/calculators/calculators.shtml
BGI - http://www.biggameinfo.com/BalCalc.aspx
The two biggest unknowns in these calculations are muzzle velocity and ballistic coefficient of the bullet. BC's are generally published by the bullet manufacturers, but the numbers are all over the place and generally are not super accurate. In addition to that, most companies use the G1 reference projectile for their BC's and that is not the best choice for most streamlined bullets. Unless you have a chronograph, your muzzle velocity is a WAG as well.
All of this leads to trajectory charts that are guesses, at best. With good data, the calculators are pretty accurate. With bad data they are garbage. This means you must test fire at a number of ranges to see how your rifle actually shoots and compare it to the charts for reference.
Mark
