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velocity vs accuracy in long range shooting

 
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Old 07-29-2012, 03:03 PM
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velocity vs accuracy in long range shooting

so my question is how accurate do you need to be for shooting long range?(1000-1300yds)

my gun is a remington 700 sps varmint in 308. (1 in 12 twist).

i am shooting 168gr sierra HPBT with RL-15 powder.

shot through my chronograph.

these are at 100yds.

the center group is 42.5gr at 2400fps and is .95".

the bottom left is 43gr at 2450fps and is the best group at .425".

the upper left is 43.5gr at 2500fps and is .815".

the upper right is 44gr at 2550fps and is 1.11". (MAX LOAD IS 44.8gr)

the bottom right 175 SMK at 44gr at 2475fps and is 1.45"(MAX LOAD IS 44.3gr)


If accuracy is the way to go i should go with 43gr of powder but velocity is only 2450.

50fps is about 2 foot difference at 1000yds.

would like to switch to 175gr buy have 300 rounds of 168gr right now.

any suggestions what i should do?

thanks in advance.
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  #2  
Old 07-29-2012, 05:06 PM
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Re: velocity vs accuracy in long range shooting

Best thing I could tell you would be to get off paper at 100 yards and move out to longer ranges doing practical field practice. That is when you go to an area where you can spot shots of opportunity, such as a very small, well defined rock, range it, dial up or hold over your shooting solution, set up for the shot and shoot as you would in the field at a big game animal.

Record your shot placement, hit or miss and if miss, by how far you missed and what direction.

Move to another range target, repeat and again, record your impact.

Do this at varying distances and then take your impact data and compare it to the drop chart to see if you can tweak the drop chart to match up better with your rifles trajectory.

Tweak your drop chart and head back out to the range and retest. Continue until your drop chart matches up perfectly with your rifles actual trajectory.

Again, more of my opinion, groups are fine but they mean very little to the long range big game hunter. They tell us if we have a good consistant load but 100 yard groups tell us very little about a rifles long range performance. I have seen many rifles that shot well at close range that did not perform worth a darn at long range. I have NEVER seen a rifle that shot well at long range NOT perform well at close range!!!

As far as what is more important to long range shooting, velocity or accuracy, simple answer is both. Velocity however is useless without accuracy so you want as much velocity as is safe and your rifle will accurately handle but if it degrades accuracy, a bit more velocity is not worth it.

If you have one load that shoots 1 moa at X fps and another load that shoots 1/2 moa but is 75 fps slower, take the 1/2 moa load, 75 fps means nothing at long range if your consistancy is degraded.

Again, test at long range. I have also seen many rifles that grouped 3/4 to 1 moa groups at 100 yards that shot into the 1/2 to 3/4 moa group size at longer ranges. This is not typical with the lower intenstity chamberings such as the 308 but with any long range bullet, generally they tighten up in moa group size as shooting range increases.

Back to my main point, find a good load and get off paper and onto practical field practice shooting instead of punching paper groups. Your rifles barrel will last much longer and you will have much more fun with your rifle and learn much more about long range shooting as well.
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  #3  
Old 07-29-2012, 10:29 PM
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Re: velocity vs accuracy in long range shooting

I've worked up a very similar load using 168 gr bullets. I use AA2520 instead of RL15. Anyway, I found two distinct accuracy nodes. The first was very near minimum. The second was right at 42.7 gr. The max for this load is 44 grains. As I went higher in the load (closer to max) I lost accuracy. The higher velocity meant nothing if I couldn't group well. So, I went with lower load. It chrono's at about 2660, which is only about 40 fps below the 2700 that factory hornady match will give you.

Go with accuracy and not the highest velocity.
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Old 07-30-2012, 04:35 AM
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Re: velocity vs accuracy in long range shooting

When I first started out ,I was shooting at 100 yards and some guys on this site told me I should move out to 200 Yards. To see what my load was doing @ 200. Once I got a decent load at 200 I checked it at 300 (if your scope will allow). I believe a person could stop at 200 and then go out . but I would shoot at paper as far as I could. Paper tells you exactly whats going on! Then I would do exactly what Kirby has mentioned. Just my opinion.

if you can get a load that shoots 1 1/2 @ 200 then you should be good to go.
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Old 07-30-2012, 06:14 AM
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Re: velocity vs accuracy in long range shooting

A lot have good points have been made. Something else to consider, particularly since you are speaking about 1000+ yards, is the 168 SMK. The bullet design, while sufficient for 700 yard work, is not the best design for the longer ranges due to the bullet profile, particularly the boat tail. This is pointed out in Litz's book. For the longer ranges I think you should go with the 175 SMK, or try one of the VLD designs. Not only will the be more stable/accurate, but as you point out, due to the higher BC, will catch up with the lower BC bullet at long range. Since you have a supply, if need be, they would sell quickly on this site, they are a great mid range bullet. I personally set an accuracy goal of .5 MOA or better, with much of my final testing done at a 500 yard range after initial results at 100/200 yards. I get best results with 43 gr. of Varget with 175's at 2550 FPS out of my MilSpec. 2700 FPS with 44gr of Varget with 168 gr. Both shoot .5 MOA or better with and ES of 5-15 FPS. I have found Varget to be very temperature stable.
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Old 07-31-2012, 07:50 AM
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Re: velocity vs accuracy in long range shooting

Most cartridges shoot most accurate at all ranges with reasonable muzzle velocities; not the highest attainable with some slow powders. And some loads producing the lowest spread in muzzle velocity and peak pressure are horrible in the accuracy department.

I've suggested that one decide what the furthest they want to miss their point of aim at a given range, then find the rifle and ammo that they can shoot groups twice that size. If you max miss from point of aim at 800 yards is 5 inches, then use something you can shoot no worse than 10 inch groups at 800 yards.

Extruded powder's been the favorite of long range competitors; ball powder's never been popular with the winners and record setters. Milder primers often produce better accuracy than the hot ones. And use bullets a few ten thousandths inch larger than your barrel's groove diameter.

Shoot enough shots per group so that the groups are meaningful; one 20-shot group's about 10 times more meaningful than five 4-shot ones, four 5-shot ones or even seven 3-shot ones. Ignore the smallest groups shot; they happen the least often and folks typically wear out their barrels trying to shoot another tiny one they did months earlier. Accuracy you can count on all the time with a given load's best represented by the largest group shot with it.

A favorite load for 24 inch 1:12 twist .308 Win. barrels at long range was 44 grains of IMR4320 under a Sierra 190-gr. HPMK match bullet. If your barrel's groove diameter is .3080" or smaller, it'll probably do well with this load. This assumes the barreled action is properly epoxy bedded and the stock screws are torqued to about 45 inch-pounds. And the barrel's got a good quality bore.

Other successful loads at long range for the .308 round with a 1:12 twist barrel....43 grains of IMR4064 under a 175 or 180 grain match bullet.
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  #7  
Old 07-31-2012, 04:59 PM
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Re: velocity vs accuracy in long range shooting

i personally will always shoot the fastest load that hangs under an inch, even if its not the most accurate. a suggestion is to try different seating depths and see if you cant get a faster, more accurate load. on a different note, i always thought 168 gr. bullets was max for a 1-12'' 308 barrel?
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