loosesniper2000
Well-Known Member
I'm guessing your chronograph is way off. Try this, borrow a buddies chronograph and shoot the same bullet through both chronographs at the same time. It pretty much has to be the only solution
Chrony/Ballistics Software Discrepancies
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Trickymissfit
Well-Known Member
I'd be begging somebody to loan me another chronograph. Then compair the readings. Your showing close to a 7% error.
gary
gary
Chronographs are at BEST a guess at the actual velocity. Every chrony maker always gives a laundry list of disclaimers explaining their inconsistent results (climate, angle of sun, etc). Take them for what they are. In similiar conditions, they are very able to give you variability between loads/reloads. This predicts ES/SD which is very useful. Correlation between chrony's and ballistic software is only useful if you shoot ALOT under many conditions. YES you have to probably adjust velocity (the easiest variable to adjust) to get your rifle to fit a mathematical curve. The space shuttle is launched based on a predicted mathematical curve. Actual velocities and environmental conditions are adjusted for in flight. Additionally, any software is also VERY susceptible to user error (i.e. stacking tolerances) as listed below.
Boomtube suggests you are "just guessing" and to get rid of all this technological "blasphemy". His blunderbuss probably shoots a cloverleaf, but to each his own!
Boomtube suggests you are "just guessing" and to get rid of all this technological "blasphemy". His blunderbuss probably shoots a cloverleaf, but to each his own!
Jay Kyle
Well-Known Member
This is why I put my chrony on the shelf and haven't used it since. At the end of the day where the bullet lands is the actual data. Any ballistic models MUST be validated and corrected against actual testing.
My approach (and most folks) is to shoot at various distances and curve-fit my ballistics software to the actual data. That way when I need to interpolate some distance I have a very high degree of confidence in recommended hold-over. The real trick is to now take that data to the field at a different set of atmospherics and see if your software can compensate for it correctly.
Jay
My approach (and most folks) is to shoot at various distances and curve-fit my ballistics software to the actual data. That way when I need to interpolate some distance I have a very high degree of confidence in recommended hold-over. The real trick is to now take that data to the field at a different set of atmospherics and see if your software can compensate for it correctly.
Jay
I had the same thing happen the other day.
Doing load development and had low velocity and high pressure.
Didn't make sense to me.
The chrono read 3150 but the drops at 565yds and 1000yds corresponded to a speed of 3250.
I bet it's closer to 3250 and my chrono was wrong.
Doing load development and had low velocity and high pressure.
Didn't make sense to me.
The chrono read 3150 but the drops at 565yds and 1000yds corresponded to a speed of 3250.
I bet it's closer to 3250 and my chrono was wrong.
MNbogboy
Well-Known Member
Maybe we have all doubted our software from time to time.....A while back I did some 300 yard shooting with one of my 260s...It is topped with a newer Elite 4200 6-24.....The Berger program told me to dial up +3.64" at 100 for the 2880 fps 130 VLD for the 300 yard zero....It shot a so-so (2+") group strung out mostly horizontal (breezy day)well over 2 inches above the mark.....This stumped me and there was nothing to adjust on the program to even get me close.....back to zero and 100 yards....five shot ragged-holes most of the time in the .3 to .5 range......A second session at the three hundred yard target again produced 2+ inch high group at just under an inch and three quarters.......Turns out after checking the distance to target with both range finders and a tape measure, all program settings, altitude, BC.....even shot over the chrono at 100 yards to see if it was way off (even though it is impossible to get that 260 going fast enough to produce the results I thought I was having)..........The Bushnell scope is advertised as 1/8 MOA clicks....that was my blunder.....My math says a one eigth MOA click has an inch value of about .130" at 100 yards....After extensive testing at 100 yards it turns out each click value is about .158"(average over testing).......Now instead of 28 clicks I tried 23....This time I blew what might have been a nice group with my second shot with a high right flyer but the next 4 hovered all within 3/4 inch of the center ring........Total group was 2 1/4".....
I know that the click value of most scopes is not exact but this one is over 20% higher than advertised.....I didn't expect that from a good mid range scope....Field testing should always be the final solution...and in my case at least the field testing not only verified the ballistic program was correct but also the chrony, and range finders....The only thing in question still is why the scope adjustments aren't even close to their advertised value...Am I missing something?.....Without knowing the internal geometry and thread pitch of the adjustment screw I can't prove it to myself...I am at the lower end of adjustment because of Burris rings and inserts....My theory is that the click value changes the farther you get out from true center but that is only a guess at this point unless somebody out there knows why......
In the mean time I look forward to plugging in the numbers and making up a few dope cards and heading down to the rifle club to try some 400, 500 and 600 yard.....I only have 100, 155 and 297 here at home....
Good Shooting,
Randy
I know that the click value of most scopes is not exact but this one is over 20% higher than advertised.....I didn't expect that from a good mid range scope....Field testing should always be the final solution...and in my case at least the field testing not only verified the ballistic program was correct but also the chrony, and range finders....The only thing in question still is why the scope adjustments aren't even close to their advertised value...Am I missing something?.....Without knowing the internal geometry and thread pitch of the adjustment screw I can't prove it to myself...I am at the lower end of adjustment because of Burris rings and inserts....My theory is that the click value changes the farther you get out from true center but that is only a guess at this point unless somebody out there knows why......
In the mean time I look forward to plugging in the numbers and making up a few dope cards and heading down to the rifle club to try some 400, 500 and 600 yard.....I only have 100, 155 and 297 here at home....
Good Shooting,
Randy
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rscott5028
Well-Known Member
You can test the full range of adjustment at 100 yds with a large sheet of cardboard or butcher paper and mark a vertical line down the center using a level or plumb bob and index the line with a yardstick. Then lock your gun in a vise or lead sled and check your scope adjustments or shoot groups while moving your turrets throughout the full range.
It's not surprising the scope is off. Rather, it's amazing how well low to mid-range scopes work these days.
Many of us remember the good old days when you'd turn your high dollar scope adjustment 4 clicks and it might move an inch or 2 inches or none at all.
-- richard
It's not surprising the scope is off. Rather, it's amazing how well low to mid-range scopes work these days.
Many of us remember the good old days when you'd turn your high dollar scope adjustment 4 clicks and it might move an inch or 2 inches or none at all.
-- richard
MNbogboy
Well-Known Member
Richard that sounds like a lot easier way than I have been doing....I used to check tracking (vertical only) by placing two pieces of masking tape on the corner of the neighbors pole barn about 2 feet apart up and down...We didn't have a gun vise and lead sleds were not invented yet....So I rubber snubbered the rifle down to a "VEE" notched cardboard box on a table and leveled the rifle......I shimmed up the box until the crosshair lined up with the bottom tape...The barn was 150 yards away (paced not measured)...1/4" clicks should cover about 3/8" at that distance.....so if we made 60-70 or so clicks up and the cross hair stayed on the corner of the building all the way up we figured the scope was not canted....That was back in the day looking for scope cant but I believe that is the same method you are talking about now to check for tracking and click value....I probably still would be doing it the old way but there is no buildings in sight of my new place
...
Thanks for the advice I have two more rigs almost ready for "dope tuning", and I am going to use your method...
Thanks again,
Randy
...Thanks for the advice I have two more rigs almost ready for "dope tuning", and I am going to use your method...
Thanks again,
Randy
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Mikecr
Well-Known Member
MNbogboy
Does it really seem like you've gained anything with a cheap scope, cheap chrono, cardboard rest, poor targets, and inaccurate ranging?
Nothing wrong with it if this is the extent of your resources, AND you recognize AND work within your actual capabilities resulting.
Everyone here who doubts their tools, and generalize that chronos are 'a guess', or that 'most scopes are not accurate', have put themselves in this sad position.
They cut corners, shoot beyond understanding, and then discredit their own approach as though it applies everywhere..
But if they had begun with an actual plan, and used the right tools to meet objectives, things would seem a whole lot different to them right now. They would be focused more on why things work, and how they might work better, instead of generalizing about nothing working.
Just sayin,, It all starts with a plan. Is this your plan?
Does it really seem like you've gained anything with a cheap scope, cheap chrono, cardboard rest, poor targets, and inaccurate ranging?
Nothing wrong with it if this is the extent of your resources, AND you recognize AND work within your actual capabilities resulting.
Everyone here who doubts their tools, and generalize that chronos are 'a guess', or that 'most scopes are not accurate', have put themselves in this sad position.
They cut corners, shoot beyond understanding, and then discredit their own approach as though it applies everywhere..
But if they had begun with an actual plan, and used the right tools to meet objectives, things would seem a whole lot different to them right now. They would be focused more on why things work, and how they might work better, instead of generalizing about nothing working.
Just sayin,, It all starts with a plan. Is this your plan?
rscott5028
Well-Known Member
Mikecr makes an excellent point. Cutting corners often ends up far more expensive. ...time, wasted ammo, barrel life...
Either way, checking your turrets doesn't have to be expensive or high tech. You just need an accurate range to the target and accurate measurements on the paper. 1/4" @ 100 yds isn't 1/4 MOA and it isn't the same as 1/4" at 110 or 90 yds either.
In terms of low end scopes, I'd have to pick repeatability over precision if stuck choosing between the two. You may need to develop a procedure for always turning up to your elevation or always from left to right for windage in order to eliminate the internal adjustment backlash that is frequently a problem.
Good luck!
Richard
MNbogboy
Well-Known Member
Mikecr & Richard,
I enjoy reading both of your posts and still am learning a lot from you guys...
Sorry if I misled you....My brain doesn't always type what I am thinking...
Back in 72 or so when I threaded my first Mcgowen barrel (they were still in ILL back then), I didn't even own a chrony yet and never dreamed that I ever would....The cardboard gun vise was my way of checking vertical tracking and I used it religiously for quite a few years just to get a scope mounted plumb (at least as plumb as the barn wall)...paying no attention to the orientation of the cross hairs and believe me the old scopes could be visually way off when they started tracking true to plumb....I was still reading Jack O'Conner back then and my goal was 1 MOA or better for decent rifles and our long range shooting back then was limited to a quarter mile or less....
I think my first post stated that there is no replacement for actual field testing...I guess that my plans and yours are very different....I have never had unlimited resources to run down and buy the latest and greatest equipment...If I spend $300 on a Shilen or Douglas barrel now, I am reasonably sure that I can make it shoot a half an inch or less at a 100 yards and If my "cheap" Chrony gives me a good representation of what my loads are doing I am happy with that (I have developed however an all weather chrony stand with an adjustable sun visor that really helps with day to day consistency)...My 100 yard chrony test will either verify software MV and 100yd velocity to actual chrony results or give you an idea that it is junk, I really believe it is a good test to help people believe their chronys...Printed ballistics were all we had thirty years ago, but today the ballistic programs really can be verified with actual field results....
My original post was just to help you guys point out to the original poster that with all the variables there is..all we can get is close and there is no substitute for field data and practice....
Thanks again and keep "shooting" out those ideas,
Randy
I enjoy reading both of your posts and still am learning a lot from you guys...
Sorry if I misled you....My brain doesn't always type what I am thinking...
Back in 72 or so when I threaded my first Mcgowen barrel (they were still in ILL back then), I didn't even own a chrony yet and never dreamed that I ever would....The cardboard gun vise was my way of checking vertical tracking and I used it religiously for quite a few years just to get a scope mounted plumb (at least as plumb as the barn wall)...paying no attention to the orientation of the cross hairs and believe me the old scopes could be visually way off when they started tracking true to plumb....I was still reading Jack O'Conner back then and my goal was 1 MOA or better for decent rifles and our long range shooting back then was limited to a quarter mile or less....
I think my first post stated that there is no replacement for actual field testing...I guess that my plans and yours are very different....I have never had unlimited resources to run down and buy the latest and greatest equipment...If I spend $300 on a Shilen or Douglas barrel now, I am reasonably sure that I can make it shoot a half an inch or less at a 100 yards and If my "cheap" Chrony gives me a good representation of what my loads are doing I am happy with that (I have developed however an all weather chrony stand with an adjustable sun visor that really helps with day to day consistency)...My 100 yard chrony test will either verify software MV and 100yd velocity to actual chrony results or give you an idea that it is junk, I really believe it is a good test to help people believe their chronys...Printed ballistics were all we had thirty years ago, but today the ballistic programs really can be verified with actual field results....
My original post was just to help you guys point out to the original poster that with all the variables there is..all we can get is close and there is no substitute for field data and practice....
Thanks again and keep "shooting" out those ideas,
Randy
rscott5028
Well-Known Member
No disagreement here.
It's all relative. How picky you get depends on how far you expect to shoot and how big your margin for error is.
Like you said, field testing is the final proof.
