308 trajectory help
09-09-2009, 04:23 AM
#4
Nontypical Buck
Join Date: Mar 2004
Posts: 2,445
Sounds right to me.
Your exact trajectory will depend on your gun, and things such as the height of your scope in relation to the bore. A basic rule of thumb is to sight in dead on at 25 yds. This will place most trajectories on the paper at 100 yds. Verify your trajectory at 100, adjust as necessary, and then verify at longer ranges, and make further adjustments as needed to establish your maximum point blank range (MPBR).
MPBR is the distance to which you do not need to adjust your point of aim. With a 308 that may be 225-250 yds. Within that range you aim dead on and shoot. The bullet will hit anywhere from 2-3" high to 2-3" low of your point of aim. If you hold dead center, that's a dead deer every time.
Your exact trajectory will depend on your gun, and things such as the height of your scope in relation to the bore. A basic rule of thumb is to sight in dead on at 25 yds. This will place most trajectories on the paper at 100 yds. Verify your trajectory at 100, adjust as necessary, and then verify at longer ranges, and make further adjustments as needed to establish your maximum point blank range (MPBR).
MPBR is the distance to which you do not need to adjust your point of aim. With a 308 that may be 225-250 yds. Within that range you aim dead on and shoot. The bullet will hit anywhere from 2-3" high to 2-3" low of your point of aim. If you hold dead center, that's a dead deer every time.
09-09-2009, 06:24 AM
#5
Nontypical Buck
Join Date: Oct 2007
Location: Southeast Alabama
Posts: 1,625
Here is a link to a ballistics calculator you can plug your info into.
http://www.biggameinfo.com/BalCalc.aspx
Remember this rule when you plug in your velocity. Most companies test their ammo with 24" barrels and you need to take about 25fps off the published velocity for every inch shorter your barrel is.
http://www.biggameinfo.com/BalCalc.aspx
Remember this rule when you plug in your velocity. Most companies test their ammo with 24" barrels and you need to take about 25fps off the published velocity for every inch shorter your barrel is.
09-11-2009, 03:54 AM
#8
Spike
Join Date: Sep 2004
Location: Mid Hudson Valley, NY
Posts: 99
Being that I really doubt that a new shooter can hold into anything near 1/8 of an inch, just sight the thing in so that the impact of the bullet is going to be 1 3/4" above the intersection of the crosshairs at whatever range you are thinking about. You may not be shooting MOA, but you should be shooting MOD. (Minute of Deer)
09-11-2009, 05:41 AM
#9
Sounds right to me.
Your exact trajectory will depend on your gun, and things such as the height of your scope in relation to the bore. A basic rule of thumb is to sight in dead on at 25 yds. This will place most trajectories on the paper at 100 yds. Verify your trajectory at 100, adjust as necessary, and then verify at longer ranges, and make further adjustments as needed to establish your maximum point blank range (MPBR).
MPBR is the distance to which you do not need to adjust your point of aim. With a 308 that may be 225-250 yds. Within that range you aim dead on and shoot. The bullet will hit anywhere from 2-3" high to 2-3" low of your point of aim. If you hold dead center, that's a dead deer every time.
Your exact trajectory will depend on your gun, and things such as the height of your scope in relation to the bore. A basic rule of thumb is to sight in dead on at 25 yds. This will place most trajectories on the paper at 100 yds. Verify your trajectory at 100, adjust as necessary, and then verify at longer ranges, and make further adjustments as needed to establish your maximum point blank range (MPBR).
MPBR is the distance to which you do not need to adjust your point of aim. With a 308 that may be 225-250 yds. Within that range you aim dead on and shoot. The bullet will hit anywhere from 2-3" high to 2-3" low of your point of aim. If you hold dead center, that's a dead deer every time.
I have a Savage .308 with a Bushnell 3-9x40 scope and was out yesterday at the outdoor WMA range for the first time in a few months. My .308 is still dead on accurate.
1" high at 100 yards from a solid bench rest. 168 gr BTHP rounds. They all hit 1/2 - 1" of each other (well, I was using a bench rest!
- ain't no way I could shoot that well by myself!)I have heard the 25 yard = 100 yard rule of thumb too, but I have never used it or verified it.
09-12-2009, 08:40 AM
#10
Fork Horn
Join Date: Jan 2009
Location: Kentucky
Posts: 201
When you mount a scope 1.5 inches above the bore, most center fire rifles (except the .30-30, .45-70, pistol cartridges) will place their bullets across the line of sight first between 23 and 27 yards, depending on velocity...this normally gives you a zero at around 200 yards, and puts you 1-2 inches high at 100 yards...and about 3-6 inches low at 250 yards...
When sighting in, I always start at 25 yards point of aim, then back to 100 yards and adjust for +1.825 inches with my 7mm RM, then out to 250 yards, and adjust for zero. This gives you a very precise rifle with a minimum use of ammo.
Another popular method lately is to zero the rifle at 200 yards with a BDC type reticle and use a laser range finder...WARNING...the BDC is terrific but not necessarily precise...the 300 yard dot may be 250-350...you really need to shoot enough to verify the distance for each...and write it down somewhere handy...
When sighting in, I always start at 25 yards point of aim, then back to 100 yards and adjust for +1.825 inches with my 7mm RM, then out to 250 yards, and adjust for zero. This gives you a very precise rifle with a minimum use of ammo.
Another popular method lately is to zero the rifle at 200 yards with a BDC type reticle and use a laser range finder...WARNING...the BDC is terrific but not necessarily precise...the 300 yard dot may be 250-350...you really need to shoot enough to verify the distance for each...and write it down somewhere handy...