drop chart versus chrono for load work up

[jasonahull]

i recently developed a drop chart for 130 berger for my 6.5x47
with a mv of 2980 based on the minutes used at different ranges.
one of my buddies has a rifle with same barrel maker and same chamber as mine, only his is an 8 twist mine is a 8.5 twist, both are 3 groove.
with the same load over a chrono, he said his mv's were 2808 averaged.
that did not add up to my drop chart which is pretty close out to 1050 yards.
so i shot over a chrono today and my load matched his mvs, 5 shots averaged 2808.
so at 300 yards i was right on with 3 moa, according to the nightforce program and jbm ballistics at 2980.
drop chart with a 2808 m.v.says 3.5 moa for 300 yards.
dialed 3.5 moa up for 300 yards i was 1.5 inches high.
i found it irritating because at 516 yards my drop chart was dead on, 4 clay pigeons in a row, plus a 2.5 inch group on paper.
any way the mv's chronographed are way off the drop chart mv's, which sucks because at 2980 with no pressure signs shooting, what i tought was pretty flat and accurate, i was happy with that load.
after looking around what i found was that you need to check to see if your scopes clicks are true 1/4 moa.
mine are not.
what i found is that my scope is off by +.029 moa per click, so each click on my scope is .279 not .250 which means at 300 yards, when my dial says 3 moa up, i am actually up 3.5 which matches my drop chart with 2808 muzzel velocity.
so for me,the next time i do load development, i will use a chronograph first, then drop chart later.
id like to say thanks to bryan litz. i figured this out after reading what he wrote about checking the value of your clicks.

 

[ReaperDriver]

Re: drop chart versus chrono for load work up

Maybe the chronograph is wrong.

 

[sobrbiker883]

Re: drop chart versus chrono for load work up

So did you actually check your clicks or adjust what you think you were dialing to match a ballistic program's prediction of where you should be with the velocity the chrono gave you?

I wouldn't blame the scope prior to actually measuring your adjustments on paper at a known distance.

Chrono's and programs never trump actual DOPE.

I'm not saying you are not correct, I'm just suggesting you verify it by shooting group at say a measured 200yds, dialing 10moa on your scope and shooting another group, then measure actual distance CTC of the groups and see what you are dialing.

If something like that is what you did, sorry to question.


-btw, Lindy's been telling folks to check their adjustments here for years!


-also did you check current weather info (like density altitude, pressure changes, temp, etc)?
I'm just trying to bang trusting DOPE in my head rather than chasing variables.......

 

[sobrbiker883]

Re: drop chart versus chrono for load work up

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ReaperDriver</div><div class="ubbcode-body">Maybe the chronograph is wrong. </div></div>
Damnit, you typed that while I was hunting and pecking my long winded spiel???

 

[jasonahull]

Re: drop chart versus chrono for load work up

i thought that too, but he shot across two thinking the same thing.
i shot across one this morning and came up similar.
i was getting mad at him because he kept telling me i was wrong but couldnt explain the difference between the chronograph and the mv's for the drop chart.
but i found out that it is common in most scopes to not have true .250 moa clicks.
my buddy lucas has a nightforce and the clicks on his are less than .250 moa
it tracks fine and box test ok.
apparently the nightforce program even has a feature to change the click value to match what your individual scope may have.
we did the math and figured my scope was more than .250 then applied it to the drop chart and it matched the velocity. so when i dial 3 moa i am actually 3.5
and in some scopes it gets worse as you get close to the end of you adjustable moa's

 

[jasonahull]

Re: drop chart versus chrono for load work up

yes i shot groups on paper and figured it that way,
i dont remember where i read it but bryan litz said to shoot at
100 yards with a tall target and go up in moa till you run out and measure the inches or something.
i have shot it all the way out to 1050. the load is accurate but i doubt 3 different chrono's could be so close in velocities.
i think i will pm bryan and ask him where i read that about testing the scope clicks

 

[matchking]

Re: drop chart versus chrono for load work up

If I had a scope that moved 35 minutes when I dialed 30 (if that is actually the case), I think I would get rid of it. Of course, you could have the flattest shooting 6.5 x 47L around based on your dope card.

 

[jasonahull]

Re: drop chart versus chrono for load work up

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sobrbiker883</div><div class="ubbcode-body">So did you actually check your clicks or adjust what you think you were dialing to match a ballistic program's prediction of where you should be with the velocity the chrono gave you?

I wouldn't blame the scope prior to actually measuring your adjustments on paper at a known distance.

Chrono's and programs never trump actual DOPE.

I'm not saying you are not correct, I'm just suggesting you verify it by shooting group at say a measured 200yds, dialing 10moa on your scope and shooting another group, then measure actual distance CTC of the groups and see what you are dialing.

If something like that is what you did, sorry to question.


-btw, Lindy's been telling folks to check their adjustments here for years!


-also did you check current weather info (like density altitude, pressure changes, temp, etc)?
I'm just trying to bang trusting DOPE in my head rather than chasing variables....... </div></div>

i agree with you on dope if i aim and hit im happy,
in eastern washington i hit targets cold bore at 450, 500, and like 640 so the chart was on.
my point is that i stopped load developing because i thought i was at different velocity.
which i dont know how much it changes energy at longer ranges which may matter if you are developing a load for hunting like i was.
i wanted max velocity without giving up accuracy. just in case i got a shot at longer ranges.
i havent checked what the difference is between the two speeds and retained energy, but when it comes to taking a shot on an animal i want all the info to be as accurate as possible.

 

[jasonahull]

Re: drop chart versus chrono for load work up

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: matchking</div><div class="ubbcode-body">If I had a scope that moved 35 minutes when I dialed 30 (if that is actually the case), I think I would get rid of it. Of course, you could have the flattest shooting 6.5 x 47L around based on your dope card. </div></div>

it is of by .5 at 300
i dont know what it would be at longer ranges. but i quess it is not uncommon for a scope to not be true quarter clicks from what i hear.
2980 isnt beyond belief, other guys are getting 2950 with shorter barrels.
i assumed from my chart and the fact that is a 28 inch barrel, 2980 was reasonable.
when i find the test i read about i will list it here.
my buddy even called nightforce about his scope, they told him it isnt uncommon, that is why their program has a spot to change the click values.

 

[jasonahull]

Re: drop chart versus chrono for load work up

if you develope a load and chrono it, when you are where you want to be, you go shooting right.
then you adjust your drop chart so you have good dope for your rifle. if your dope calls for say 8 minutes at 500 yards and you actually need 8.25, why is that if you have your mvs figured out
or maybe at 500 yards your dope is 7.50 and you need 8 why is that if you have the mv's?
most people shoot different ranges and fine tune their charts so they have good dope all the way out to where they plan to shoot.
what i read some where is those differences can be the clicks in your scope not being true .250 moa.
none of that matters if you have a scope that tracks, know your mvs and have a drop chart that is on for your load and scope.
i developed my load from data from different web sites and shot at 100 and 300 and 500 600 900 1050 with a repeatable drop chart.
i only used a drop chart to determine velocity.
the drop chart says 2980 is the mv. the chrono says 2808 the difference being 172fps
my scope clicks are .279 moa instead of .250 which makes it seem that bullet was going faster, by .5 moa @ 300 yards.
some test loads needed only 2.5 moa for 300 yards with a .552 bc, that would be a laser beam so it has to be off. when in reality it was more like 3 moa which is where i wanted to be. but because i thought that load was "hot" i went with a lower powder charge.
i guess my point is that if you only use a drop chart method for load developing, it may be handy to know what the true adjustments are on your scope.
it doesnt matter if it is off + or - if it tracks correctly and you have repeatable accuracy.
i just dont think without knowing the true value of the clicks, that i would trust the mv's based off of a drop chart only.

 

[Greg Langelius *]

Re: drop chart versus chrono for load work up

The world of numbers is a lot simpler than the world of bullet holes. Calcs accept data and make (very accurate) assumptions about factors that may or may not be consistent with reality, or the totality of real conditons.

Calcs will get you into the ball park, but precise first round hits using calc data are rare enough to be indistiguishable from luck. Close, yes; precise, seldom.

Until you shoot it, adjust it, and confirm it; it's all just a pleasant fiction.

Greg

 

[sobrbiker883]

Re: drop chart versus chrono for load work up

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: h.b.h.l.r</div><div class="ubbcode-body">yes i shot groups on paper and figured it that way,
i dont remember where i read it but bryan litz said to shoot at
100 yards with a tall target and go up in moa till you run out and measure the inches or something.
</div></div>

Don't bother PMing bryan, I understand how and why to check out your scope's clicks.

From the above statement it does not sound like you have tested your scope's adjustment on paper at 100 by dialing a large amount of adjustment and measuring what the scope actually tracked. I mentioned groups, because when I check a scope I measure center to center of groups shot at each end of the adjustment change-better data than taking one shot, dialing, taking one shot.

Chrono's are nice, but load development (for me at least) has nothing to do with a speed number I have in mind. Load development is about finding an accurate load. If you want an accurate fast load, load up in increments until you find pressure signs, then ladder test/OCW test around there to find the accuracy node.

I only chrono a load after I've found a load that runs well, then I tweak the ballistics program to get data that matches my field DOPE at those conditions, just so I have a reference that I can generate data for different environments if I need it.

If you have gotten out the big target and tested your scope and it is indeed off by 11.6% on its adjustments, would you care to share what scope it is?




<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">
Until you shoot it, adjust it, and confirm it; it's all just a pleasant fiction.

Greg </div></div>

 

[jasonahull]

Re: drop chart versus chrono for load work up

http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1447650&#Post1447650
this is where i read it. i havent done a complete test but is is off enough to where i see the importance of it.

 

[jasonahull]

Re: drop chart versus chrono for load work up

the point to this is, i have a good drop chart that i am confident in, but the velocity is way off based on a drop chart.
that is all.
personally i like to know the real numbers on clicks, mv's everything.
the possibility of scope clicks not being true .25moa is something i recently learned.
i agree, load until you have a good one, chrono it, then develope your chart.
i also think if you test your scopes adjustments and have the correct clicks it will make an accurate drop chart easier.

 

[matchking]

Re: drop chart versus chrono for load work up

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: h.b.h.l.r</div><div class="ubbcode-body"> it is of by .5 at 300
i dont know what it would be at longer ranges. but i quess it is not uncommon for a scope to not be true quarter clicks from what i hear.
2980 isnt beyond belief, other guys are getting 2950 with shorter barrels.
</div></div>
If it moves 3.5 MOA when 3 MOA is dialed, then it would move 35 MOA when 30 MOA is dialed - or a bigger problem exists. I realize that without a tracking test, you have no idea how far off it is.

I also don't think 2980 "is beyond belief", but the point I was making is "if" your scope was as off as much as you think, your dope at 1000 would appear to be very flat. You would probably need 24 MOA or less dialed on your scope for a hit.

Of course, until the tracking is confirmed, no one knows. I tested a new scope yesterday and it tracked like a champ and in true MOA. I was pleasantly suprised.

 

[jasonahull]

Re: drop chart versus chrono for load work up

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: matchking</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: h.b.h.l.r</div><div class="ubbcode-body"> it is of by .5 at 300
i dont know what it would be at longer ranges. but i quess it is not uncommon for a scope to not be true quarter clicks from what i hear.
2980 isnt beyond belief, other guys are getting 2950 with shorter barrels.
</div></div>
If it moves 3.5 MOA when 3 MOA is dialed, then it would move 35 MOA when 30 MOA is dialed - or a bigger problem exists. I realize that without a tracking test, you have no idea how far off it is.

I also don't think 2980 "is beyond belief", but the point I was making is "if" your scope was as off as much as you think, your dope at 1000 would appear to be very flat. You would probably need 24 MOA or less dialed on your scope for a hit.

Of course, until the tracking is confirmed, no one knows. I tested a new scope yesterday and it tracked like a champ and in true MOA. I was pleasantly suprised. </div></div>


my scope tracked and even box tested good
and at 1050 the dialed moa was like 26
so i will be testing all of my scopes from now on to see what the actual moa clicks are.

 

[jasonahull]

Re: drop chart versus chrono for load work up

from what i have read a scope can track good and box test good and still not be true moa clicks.

 

[sobrbiker883]

Re: drop chart versus chrono for load work up

When one says "box test good" that usually means that it moved the indicated amount of dialed change, not just that it went up over down and back to original point of aim.

There's no way to definately know how much your adjustments are without shooting it, adjusting a large change and shooting it again, then measuring the movement. Interpolating what the clicks are from adjustment needed at certain distances and MV from a chrono and a ballistics program's projected trajectory have too many individual variables to quantify.

 

[dmgreene]

Re: drop chart versus chrono for load work up

One thing to remember when checking your scope travel at 100 yards-MAKE SURE that it is 100 yards. Some people will step off 100 steps and call it 100 yards and it may be 91 or 96 or whatever. If its only 92 yards then you will be off by 8% when you measure between your groups which will cause problems when trying to make drop charts work out.

David

 

[Lindy]

Re: drop chart versus chrono for load work up

That's good advice. I measure my yardage for such tests using a 100 foot tape.

 

[Sniper1*]

Re: drop chart versus chrono for load work up

I went thru this with my new USO 1.8x10!

I sent it back and they fixed it!

A buddy was doing the same thing with his Bushnell 6500 and found that his was .27x"(inches) per click instead of .262" (inches) per click!

I always run a vertical (and horizontal tracking drill) with my scopes!

Dial 2 shoot 3 rounds
Dial 4 shoot 3 rounds
Dial 8 shoot 3 rounds
Dial 16 shoot 3 rounds
Dial 20 shoot 3 rounds
Dial 24 shoot 3 rounds
all the way until I run out of target or adjustments.

I usually do this by making a perfectly vertical line and horizontal line and put a 1" orange paster right at the intersection of the lines. The orange paster is the POA for all shooting. I use a level to make sure the lines are plumb/level on the target before shooting.

After shooting vertical strings and horizontal strings left and right I rezero and make sure that is one also.

I then take the target back to the office and measure the actual center of the groups for each adjustment. Then do the math to figure out exactly how much each click moved my bullet impact. i.e. Adjusted 20 MOA (IPHY in my case) group is 20.5" up from POA. Divide 20.5 (inches) by the number of clicks 80 (20 MOA x 4 = 80) = .25625" per click!

Good luck!

USO Tracking Issues!

 

[jasonahull]

Re: drop chart versus chrono for load work up

i am not using that scope any more, so it is what it is but the next rifle and scope set up will be fully tested to make sure i know what is what.

so if a scope doesnt have true .250 mao but tracks repeatable, is the scope no good or would adjusting for it in like the exbal program be ok, i am asking cause i dont know.

 

[sobrbiker883]

Re: drop chart versus chrono for load work up

JBM allows you to put out data in .XXX of moa.

 

[Sniper1*]

Re: drop chart versus chrono for load work up

I would say as long as it is not too far off! I would keep it and make my adjustments accordingly.

 

[jasonahull]

Re: drop chart versus chrono for load work up

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sobrbiker883</div><div class="ubbcode-body">JBM allows you to put out data in .XXX of moa. </div></div>

if you do the test and figure out your true clicks i think exbal does too.

 

[jasonahull]

Re: drop chart versus chrono for load work up

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sniper1*</div><div class="ubbcode-body">I went thru this with my new USO 1.8x10!

I sent it back and they fixed it!

A buddy was doing the same thing with his Bushnell 6500 and found that his was .27x"(inches) per click instead of .262" (inches) per click!

I always run a vertical (and horizontal tracking drill) with my scopes!

Dial 2 shoot 3 rounds
Dial 4 shoot 3 rounds
Dial 8 shoot 3 rounds
Dial 16 shoot 3 rounds
Dial 20 shoot 3 rounds
Dial 24 shoot 3 rounds
all the way until I run out of target or adjustments.

I usually do this by making a perfectly vertical line and horizontal line and put a 1" orange paster right at the intersection of the lines. The orange paster is the POA for all shooting. I use a level to make sure the lines are plumb/level on the target before shooting.

After shooting vertical strings and horizontal strings left and right I rezero and make sure that is one also.

I then take the target back to the office and measure the actual center of the groups for each adjustment. Then do the math to figure out exactly how much each click moved my bullet impact. i.e. Adjusted 20 MOA (IPHY in my case) group is 20.5" up from POA. Divide 20.5 (inches) by the number of clicks 80 (20 MOA x 4 = 80) = .25625" per click!

Good luck!

USO Tracking Issues! </div></div>

i looked at your link.
the clicks you had there are similar to my buddy's nightforce, a little less than .250

 

[Sniper1*]

Re: drop chart versus chrono for load work up

My USO worked out to 7/8" per 4 clicks! Or .21875" per click!

 

[jasonahull]

Re: drop chart versus chrono for load work up

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sniper1*</div><div class="ubbcode-body">My USO worked out to 7/8" per 4 clicks! Or .21875" per click! </div></div>

is that what was or is now?

 

[jasonahull]

Re: drop chart versus chrono for load work up

my brother ordered a uso about a week ago.
it will be interesting to see what his works out to.

 

[jasonahull]

Re: drop chart versus chrono for load work up

sniper1 your buddy had a 6200
mine is a 4200 and the clikcs worked out to .279

 

[Sniper1*]

Re: drop chart versus chrono for load work up

It was 7/8 per four clicks! It is now 1" per 4 clicks as it should be in the IPHY format.

Yeah, could be the 6200 (not sure) but yeah, the .279 sounds about right!

 

[jasonahull]

Re: drop chart versus chrono for load work up

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: h.b.h.l.r</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Sniper1*</div><div class="ubbcode-body">I went thru this with my new USO 1.8x10!

I sent it back and they fixed it!

A buddy was doing the same thing with his Bushnell 6500 and found that his was .27x"(inches) per click instead of .262" (inches) per click!

I always run a vertical (and horizontal tracking drill) with my scopes!

Dial 2 shoot 3 rounds
Dial 4 shoot 3 rounds
Dial 8 shoot 3 rounds
Dial 16 shoot 3 rounds
Dial 20 shoot 3 rounds
Dial 24 shoot 3 rounds
all the way until I run out of target or adjustments.

I usually do this by making a perfectly vertical line and horizontal line and put a 1" orange paster right at the intersection of the lines. The orange paster is the POA for all shooting. I use a level to make sure the lines are plumb/level on the target before shooting.

After shooting vertical strings and horizontal strings left and right I rezero and make sure that is one also.

I then take the target back to the office and measure the actual center of the groups for each adjustment. Then do the math to figure out exactly how much each click moved my bullet impact. i.e. Adjusted 20 MOA (IPHY in my case) group is 20.5" up from POA. Divide 20.5 (inches) by the number of clicks 80 (20 MOA x 4 = 80) = .25625" per click!

Good luck!

USO Tracking Issues! </div></div>

i looked at your link.
the clicks you had there are similar to my buddy's nightforce, a little less than .250 </div></div>

i wonder if there is somehing made, or if it would be easy to make one, something that would use like a laser bore sighter that you could move up in one inch adjustments and then check your scope that way without firing a shot?
you could move it up in the same way up 2 up 4 up 8 ect. would that work?

 

[Clark]

Re: drop chart versus chrono for load work up

Everett WA?

When does the wind stop gusting, so you can make such small measurements?

 

[RemingtonSPS]

Re: drop chart versus chrono for load work up

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Clark</div><div class="ubbcode-body">Everett WA?

When does the wind stop gusting, so you can make such small measurements? </div></div>

daybreak and sunset

 

[RemingtonSPS]

Re: drop chart versus chrono for load work up

A friend of mine called NF about his clicks being off and they made an interesting point. They said to measure with a caliper from the bottom of the body to the top of the turret, then come up 1 click and measure again. Then you will see how fine the mechanism is for adjusting. Its an interesting point, you are dealing with a very fine level of adjustment and it would be extremely difficult to get a perfect .250 adjustment. This is why most if not all manufacturers are just a little off. If it is off by a considerable amount obviously they would fix it but it seems like +/- .020" adjustment is considered acceptable tolerances to most manufacturers. Like stated above it matters little as long as (1) It does not change in value as you go up in elevation, and (2) you measure the click value so as to have an accurate drop chart.

When you do the typical box test at 100yds you are changing POI by 4 moa. The impact would be about 3/8" differece on the extremes which would probably be indestinguishable on the POI during the box test.

 

[Lindy]

Re: drop chart versus chrono for load work up

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">When you do the typical box test at 100yds you are changing POI by 4 moa.</div></div>

I never do a box test for elevation on less than what I need to get to 1000 yards. It's a good idea to do intermediate steps, too, so you'll know if the increments are linear.

And you can tell a lot about a scope without shooting. See:

Optically Checking Rifle Scopes

 

[jasonahull]

Re: drop chart versus chrono for load work up

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">When you do the typical box test at 100yds you are changing POI by 4 moa.</div></div>

I never do a box test for elevation on less than what I need to get to 1000 yards. It's a good idea to do intermediate steps, too, so you'll know if the increments are linear.

And you can tell a lot about a scope without shooting. See:

Optically Checking Rifle Scopes

</div></div>
thanks for the link, i will do the yard stick test on my next scope. i like the idea of testing without having to shoot.