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velocity vs accuracy in long range shooting

 
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  #8  
Old 07-31-2012, 05:26 PM
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Re: velocity vs accuracy in long range shooting

I think there are teo important things to consider...

First, talking about speed, the distance where your bullet falls from supersonic to subsonic. Maybe 1k+ is too long for the 2450 Load... I haven't calculate it.

Second, keep in mind the bullet energy and performance at those ranges. You are talking about hunt game, not punching paper or hitting stones. Yor rifle, load, bullet, scope and, of course, you, should be able to hit the animal and kill it as fast as possible. Hitting a deer on the butt and make it hurt and run away is an insane idea.

Hope you can understand my english... Sorry for the mistakes!
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  #9  
Old 07-31-2012, 05:35 PM
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Re: velocity vs accuracy in long range shooting

You'll save time, money and barrel life and be a more consistent shooter if you do what Kirby said.

Keep in mind that a 1.5 MOA system including rifle, shooter and environment places shots only .75 MOA from center. The trick is to know which direction from center.
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  #10  
Old 07-31-2012, 06:04 PM
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Re: velocity vs accuracy in long range shooting

Quote:
Originally Posted by mrbigtexan View Post
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?
with the max wieght for 1 in 12" i've seen that 175 are good and above that are hit and miss with different barrels
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  #11  
Old 07-31-2012, 06:28 PM
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Re: velocity vs accuracy in long range shooting

thinking about testing the 175gr SMK more but before i do, has anyone tried the 155 gr. Palma Match? B.C. is .447 and above 2900fps.

Suppose to be as good as the 175SMK.

Also my bullets are seated just off the lands not sure how much.

how can playing with the seating depth add or decrease fps? i understand the accuracy part of it.




SCOPE IS Mark 4 6.5-20x50mm LR/T 1/4moa.
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  #12  
Old 08-01-2012, 12:31 AM
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Re: velocity vs accuracy in long range shooting

Quote:
Originally Posted by wisdeerkiller View Post
with the max wieght for 1 in 12" i've seen that 175 are good and above that are hit and miss with different barrels
The big difference in barrels is their length. They gotta be long enough to shoot 180-gr. and heavier bullets fast enough to remain supersonic at long ranges.

In the 1960's, the US Army Rifle Team replaced the 172-gr. match bullet in M118 7.62 NATO match ammo with a Western 180 gr. FMJ match bullet or a Sierra 180 HPMK bullet; sometimes adding a half grain of powder to what was already used for the 172 grain ones. They shot it in their M14NM's 22 inch barrel winning lots of matches and setting records, too. That was a stout load but the M14NM's handled it very well.

Folks have shot 200 grain match bullets from 26 inch .308 Win. barrels with a 1:11 twist and 220's with a 1:10 twist; winning matches and setting records doing it. David Tubb used a 28 inch long 1:8 twist barrel shooting Sierra 250-gr. match bullets out at 2150 fps; they were still supersonic through 1000 yards and shot sub MOA test groups at that range.

Last edited by Bart B; 08-01-2012 at 01:03 AM.
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  #13  
Old 08-01-2012, 12:50 AM
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Re: velocity vs accuracy in long range shooting

Quote:
Originally Posted by wisdeerkiller View Post
thinking about testing the 175gr SMK more but before i do, has anyone tried the 155 gr. Palma Match? B.C. is .447 and above 2900fps. Suppose to be as good as the 175SMK.
As one of the Palma Team members who helped develop the first loads for that bullet when prototypes were given to us in early 1991, I can attest to its accuracy as I shot the high 5-day aggregate score in the first match it was used. It quickly became a favorite. 29 inch barrels are about minimum so they can be shot at least 2900 fps to remain supersonic through 1000 yards. After they were first used in a big long range match in late 1991, top long range competitors from around the world shooting them said they'd never shot bullets that accurate. A couple dozen of them told me they shot no worse than 1/2 MOA at 600 yards; not too shabby for new cases, metered powder charges with a 1/3 grain spread and bullet runout of up to 3/1000ths. Soon thereafter, that 155-gr. bullet was set as the standard for all long range matches shot under the International Palma Committee's rules. In the USA, the shooters handload those bullets. In other countries, they aren't allowed handloads and have to use arsenal ammo that's loaded with Sierra 155's in their big matches.

The half dozen of us developing and testing loads were quite pleased with our work and since then, when IMR4895 was the powder of choice, Varget is now a better choice. And now there's a newer version with higher BC that's supposed to be better. I shot one test group in 1992 at 800 yards with the resultant load; 45.3 grains of IMR4895, Sierra 155 seated to touch the lands + .010", Federal 210M primer in a Winchester unprepped case full length sized: here's the 20-shot test group with shots 1 and 2 being the first two from a cold, clean barrel:



Quote:
how can playing with the seating depth add or decrease fps? i understand the accuracy part of it.
The less jump to the rifling there is, the higher the muzzle velocity is. It doesn't change very much and some folks are hard pressed to tell the difference between 50/1000ths jump and zero jump. Pressure's also higher with shorter jumps to the lands. Sometimes one has to cut their charge by a grain if the seat bullets to jam into the lands when loaded, but that's typically what produces the best accuracy.
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  #14  
Old 08-01-2012, 10:00 AM
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Re: velocity vs accuracy in long range shooting

First don't get twisted up about 25 fps or even 50 fps because your muzzle velocity spread if properly done will tell you a lot more and help you a whole lot more than that little bit of velocity.

Lower muzzle velocity deviation means less vertical dispersion FACT do the math on your load and you will see what just 35fps will do high to low. Your group shooting is subject to too many variables to even go into here but we will assume you are set up perfect and your technique is perfect on the bench for you load evaluation.

Groups at 100 yards mean squat at 1k—there is No correlation at all and if anyone tells you different they have never shot long range BR and been successful. To properly evaluate the pills you are using start at 300 or 400 if possible and go from there on development. When shooting LR consistency is the overall key to being successful. Being able to get the rifle and load to shoot the same every time THEN you can work on things like judging condition which is the single most important variable besides set up you will face in your quest.
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