600 yard question

[alessio]

Sorry if this question has been ask before, but I am new to the site. I built a 6BR 1-8 twist, shooting 105 gr Bergers. I have been working on load developement, and due to lack of range space, can only shoot at 300 yards. My question is, in anyone's oppinion, what is an acceptable size 5 shot group at 300 yards that would put me in the nieghborhood for competition at 600 yards? Thanks for your time,....Rob Alessio

 

[Greg Culpepper]

Rob,

300 yds is a good distance for long range load development; far enough to reveal performance and close enough to reduce noise from conditions. Tune for minimum vertical. Don't worry about the width of your groups during development. A moderate crosswind is easiest do deal with. Tail or headwinds will obscure your results.

Half an inch of vertical at 300 is golden. One inch of vertical at three hundred and you have a tool that will be instructive of your technique and get you somewhere in the fat middle of group size distribution at any match. Around 30.3 gn Varget with your setup will probably satisfy. RL 15 is another popular and proven powder for your combo. Seating your bullets a few thou. off the lands will probably work.

Good luck!

Greg

 

[Bill Ohio]

Sorry if this question has been ask before, but I am new to the site. I built a 6BR 1-8 twist, shooting 105 gr Bergers. I have been working on load developement, and due to lack of range space, can only shoot at 300 yards. My question is, in anyone's oppinion, what is an acceptable size 5 shot group at 300 yards that would put me in the nieghborhood for competition at 600 yards?

It doesn't work that way. To be competitive at 600y, you need to shoot at 600y, and find out. It's not just twice as far, i.e. it's not a linear difficulty progression. Decide on what sort of competitive shooting you want to try, and then go watch a match or two. Then gather your gear and try it.

 

[Lynn]

1 inch groups at 300 then take it on out to 600 and shoot a match.
Waterboy aka Lynn

 

[MARKS]

alessio,
I will have disagree with Bill. I started shooting 600 yds IBS when it started in 2004 and I have not fired any load development at 600 yds, and don't know of many guys that do, because of range. All I have is 200yds. I like to see 0.4" or less at 200.

Mark Schronce

 

[mks]

Tune for minimum vertical.

Rob,
Once you get a few matches under your belt, consider this:

To eliminate vertical at 600 yards, you need to tune such that slow bullets strike higher than fast bullets at 300. For example for a 600 yard zero, a 2890 fps bullet will be 28.06" high at 300, and a 2910 fps bullet will be 27.62" high at 300. That is 0.44" of vertical that you want to tune into the rifle at 300 to get zero vertical at 600 for an ES of 20 fps. YMMV with the air density you feed into your external ballistics program.

Cheers,
Keith

 

[Greg Culpepper]

Wow!

Keith,

That is one nuanced tuning program you've got going there! I haven't got the ability to discern the varying demands of 300, 600 and 1000 yd. rifle tuning. In fact, I don't tune until something quits working or I start a new equipment or ammo program with unknown (to me) variables. I think (hope) I can recognize when something has taken a dump. Of course if you don't stay after it you'll find out in a match when it counts. But I think if it works at 300 yd. it will work at 600 and 1K yd. as well.

Greg

 

[mks]

Keith,

That is one nuanced tuning program you've got going there! I haven't got the ability to discern the varying demands of 300, 600 and 1000 yd. rifle tuning. In fact, I don't tune until something quits working or I start a new equipment or ammo program with unknown (to me) variables. I think (hope) I can recognize when something has taken a dump. Of course if you don't stay after it you'll find out in a match when it counts. But I think if it works at 300 yd. it will work at 600 and 1K yd. as well.

Greg

Greg,
I'm no tuning guru, far from it. Just some observations based on plugging numbers into an external ballistics program. Put another way, if you eliminate vertical at 300 yards for ammo with 20 fps ES, you will have over 0.8" of vertical at 600. Again, this depends on air density, and scope height, too. With record agg's now under 2" this is worth worrying about. You can eliminate part of the vertical by reducing ES, but some spread is bound to remain. The rest you can try to tune out by using ammo intentionally loaded with increments in muzzle velocity (ladder test). If your test range is not 600 yards, then you can use a shorter range and look to achieve the amount of vertical at the shorter range that will eliminate vertical at 600.

Cheers,
Keith

 

[Greg Culpepper]

Keith,

Do you believe the optimum load for 300 is different than optimum for 600 which in turn is different for 1k yd?

If it is do you think you can find it?

I know I can't. And I couldn't explain the difference between a 300 yd tune and a 600 yd. tune with a ballistics program either because I can't assume a zero group with a 20 fps es

Notice I didn't write "eliminate" vertical. I wrote "minimize".

If I get vertical down to 1/2" I go home and load for a match. Sometimes I go home before then!

I don't think you're going to get zero vertical at 300, 600 or 1k yd. with a load that shows 20 fps extreme spread or with any load for that matter.

What I do know is that if you get vertical down to 1/2" at three hundred with a long range bench rifle you are ready to go to war (sorry, forgot this was just for fun) at both 600 and 1K.

Greg

 

[Bnhpr]

Rob,
Once you get a few matches under your belt, consider this:

To eliminate vertical at 600 yards, you need to tune such that slow bullets strike higher than fast bullets at 300. For example for a 600 yard zero, a 2890 fps bullet will be 28.06" high at 300, and a 2910 fps bullet will be 27.62" high at 300. That is 0.44" of vertical that you want to tune into the rifle at 300 to get zero vertical at 600 for an ES of 20 fps. YMMV with the air density you feed into your external ballistics program.

Cheers,
Keith

Interesting discussion, but it is impossible for a ballistic spread to improve over distance. e.g. a group with .5" of vertical spread ay 300 yds cannot be less than .5" at 600 yards. In any system, you are bound by the laws of physics. Entropy always increases in simple systems....organization always progresses to chaos.

 

[mks]

Interesting discussion, but it is impossible for a ballistic spread to improve over distance. e.g. a group with .5" of vertical spread ay 300 yds cannot be less than .5" at 600 yards. In any system, you are bound by the laws of physics. Entropy always increases in simple systems....organization always progresses to chaos.

The slow bullet must be launched higher than the fast one to strike the same point on the 600 yard target, thus will strike the 300 yard target higher.

Cheers,
Keith

 

[Bnhpr]

The slow bullet must be launched higher than the fast one to strike the same point on the 600 yard target, thus will strike the 300 yard target higher.

Cheers,
Keith

Ok, I understand your point.

I occasionally run across the urban legend of accuracy and long range, where people claim a load can improve it's moa at longer distances.

 

[mks]

Keith,

Do you believe the optimum load for 300 is different than optimum for 600 which in turn is different for 1k yd?

If it is do you think you can find it?

I know I can't. And I couldn't explain the difference between a 300 yd tune and a 600 yd. tune with a ballistics program either because I can't assume a zero group with a 20 fps es

Notice I didn't write "eliminate" vertical. I wrote "minimize".

If I get vertical down to 1/2" I go home and load for a match. Sometimes I go home before then!

I don't think you're going to get zero vertical at 300, 600 or 1k yd. with a load that shows 20 fps extreme spread or with any load for that matter.

What I do know is that if you get vertical down to 1/2" at three hundred with a long range bench rifle you are ready to go to war (sorry, forgot this was just for fun) at both 600 and 1K.

Greg

Greg,
The external ballistics program is just spitting out the effect of muzzle velocity variations, not all the other factors that cause dispersion. If you are getting vertical down to 0.5", then you are in a good position to recognize the effects of additional vertical caused by intentionally varying muzzle velocity. Measure muzzle velocity of each shot with a chronograph and measure the elevation of each bullet hole on the target. Plot a graph of elevation versus muzzle velocity. This is the ladder test that has been discussed a number of times. What you want to find is a spot of the 300 yard graph where elevation decreases at a rate of 0.44" per 20 fps increase in muzzle velocity to eliminate vertical at 600 due to this one source of vertical dispersion. If the first graph doesn't have such a spot, then there are many ways of changing the shape of the plot, including barrel and stock stiffness, weight distribution of the rifle and how the rifle is supported on the rests.

Yes, the optimum load/tune is different for each yardage. For instance, for a 1000 yard zero and the same bullets with 20 fps ES, the slow bullet must strike about 1.4" higher at 300.

Cheers,
Keith

 

[expiper]

practice-practice-then shoot some more

Hi Rob...you have been given some insight into testing/shooting by some past and current winners/record holders, that should be helpful to your learning curve. I do most of my "load development" here at my bakyard range which is only 100-200 yd capable....dont think that you need a target cam hooked to your laptop puter along with chronograph and weather station...!!...to figger out what your gun likes ...it will tell you...a 3 foot piece of surveyors ribbon tied to a milk weed 1/2 way down range will tell more than one of them pocket humidistat/density/temp gizmos....it your groups (at 300yds) are not much taller than .5-.7" and not much wider than an inch,you are there...but if they are taller than wide then add a lil' powder..grin...and if they are big (over an inch) and round ,fiddle with seating depth and neck tension...generally more jam and more tension will be the cure.....once I get mine to shootin bug holes at 100-200, I am ready to take it to the county fair,,,you do not need a computer or weather station to shoot well,,,spend your money on bbls.-bullets-powder.....Roger

 

[alessio]

Thank you!!!

Thank you for all the great information. I really appreciate all of you time and effort to bringing me up closer to speed. Your responces will be stored for future information and reference.

 

[alessio]

Thank you!!!

Thank you for all the great information. I really appreciate all of your time and effort to bringing me up closer to speed. Your responces will be stored for future information and reference. Thanks again....Rob Alessio

 

[Greg Culpepper]

Greg,
The external ballistics program is just spitting out the effect of muzzle velocity variations, not all the other factors that cause dispersion. If you are getting vertical down to 0.5", then you are in a good position to recognize the effects of additional vertical caused by intentionally varying muzzle velocity. Measure muzzle velocity of each shot with a chronograph and measure the elevation of each bullet hole on the target. Plot a graph of elevation versus muzzle velocity. This is the ladder test that has been discussed a number of times. What you want to find is a spot of the 300 yard graph where elevation decreases at a rate of 0.44" per 20 fps increase in muzzle velocity to eliminate vertical at 600 due to this one source of vertical dispersion. If the first graph doesn't have such a spot, then there are many ways of changing the shape of the plot, including barrel and stock stiffness, weight distribution of the rifle and how the rifle is supported on the rests.

Yes, the optimum load/tune is different for each yardage. For instance, for a 1000 yard zero and the same bullets with 20 fps ES, the slow bullet must strike about 1.4" higher at 300.

Cheers,
Keith

So Keith,

I noticed you had a lot of suggestions for what I should do to improve my tune.

Is this how you tune?

What is the difference among your 300, 600 and 1K yd. loads?

I presume you have gotten "a few matches under your belt" How is this approach working out for you in those matches, or is this more of a theoretical exercise?

Greg

 

[Flykiller]

Good info

I would like to thank you guys for sharing info. I have zero match experience. All the things you have talked about here makes sense to me, but what do i know. I wil be back on here come summer asking for more info. Hopefully that will be when i have the last back stop finished at my range in north central ky.
Presently we have back stops at 100,200,300,400,and 500. I am hopeful i can have 600 finshed by May. Thanks again for sharing because i won"t know where to start. Clint

 

[therifler]

600 yd ?

some sound advice i received from one of the best 3/4 inch at 300yds. and you will have something that will not shame you at 600yd. it can always be better but you can burn barrels up looking for perfection . T.R .

 

[mks]

How is this approach working out for you in those matches, or is this more of a theoretical exercise?

Greg

Greg,
Theoretical for me. You make a good point about just shooting and having fun, but there are some who also have fun analyzing things. VarmintAl shows a graph of the vertical caused at long range by zeroing at short range (http://varmintal.com/aeste.htm), if you are interested. 6mmBR.com had an article recently (Nov 6) on tuning out vertical by adjusting the position of the rifle in the rests ("Joel Kendrick, past IBS 600-yard Shooter of the Year, has observed that by adjusting forearm position on the front rest, he can tune out vertical."), which makes sense to me from a theoretical point of view, too. Whatever way you want to shoot, have fun.

Cheers,
Keith