barnesuser28
Well-Known Member
Now Broz, based on you experience, if my chronograph is lying to me will its error be a certain percentage or always be off say 100 fps?
Ballistics Problem
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Broz
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Riley, I wish I had a solid answr for you on that, but it could be like this. I use to line 3 Shooting Chrony's on a 2x6 and shoot through 2 or 3 of them. They were all different on the same bullet. One was 40 to 60 fps faster no matter where you placed it (first or last) one was pretty consistant but slower and one would bounce around either side of the other two...
.. But hey here is what I can tell you for sure. If you use the suggested BC from the bullet mfg. And do actual field drops to 1000 yards. Then using those drops change the muzzle velocity to match the actual dial ups needed to center the groups you shot at a given distance. You will be pretty darn good to 1000 or 1200 yards.
After that you may have to go in and play with BC's.
It is like this. It's all math, and just numbers. I don't care if it says my muzzle velocity is - 250 fps as long as I hit center target. (the -250 is a joke to make my point) This is why you hear me always talking about "Actual Field Tests Rule!!" A guy (and I see this all the time) sets at home on his PC and runs all these bogus numbers and convinces himself that velocity is king. Albeit velocity is important, but if you don't really have it, all those wanna be velocity, drift and drop numbers are just a batch of over sweetened "coolaid". Just shoot your rifle all you can my friend and then make that ballistic program match the rifle. You will then make plenty of your share of one shot kills.
Jeff
.. But hey here is what I can tell you for sure. If you use the suggested BC from the bullet mfg. And do actual field drops to 1000 yards. Then using those drops change the muzzle velocity to match the actual dial ups needed to center the groups you shot at a given distance. You will be pretty darn good to 1000 or 1200 yards. After that you may have to go in and play with BC's.
It is like this. It's all math, and just numbers. I don't care if it says my muzzle velocity is - 250 fps as long as I hit center target. (the -250 is a joke to make my point) This is why you hear me always talking about "Actual Field Tests Rule!!" A guy (and I see this all the time) sets at home on his PC and runs all these bogus numbers and convinces himself that velocity is king. Albeit velocity is important, but if you don't really have it, all those wanna be velocity, drift and drop numbers are just a batch of over sweetened "coolaid". Just shoot your rifle all you can my friend and then make that ballistic program match the rifle. You will then make plenty of your share of one shot kills.
Jeff
barnesuser28
Well-Known Member
Ok Jeff, thanks i really appreciate it!Riley, I wish I had a solid answr for you on that, but it could be like this. I use to line 3 Shooting Chrony's on a 2x6 and shoot through 2 or 3 of them. They were all different on the same bullet. One was 40 to 60 fps faster no matter where you placed it (first or last) one was pretty consistant but slower and one would bounce around either side of the other two...
Jeff
Broz
Well-Known Member
My pleasure Riley. You are getting ready to do some great hunting this coming season. I look forward to your reports. There is a young man your age down the road here. I was with him when he took a perfectly placed shot on his first buck antelope bedded at 650 yards. The young hunter was 12 yrs old then. The buck never stood up and had a hole right through his heart. Thats what it all about man!!
Jeff
barnesuser28
Well-Known Member
Thanks Jeff, i have two doe antelope tags for Wyoming (I think i am going to use my Dads Ruger M77 257 Roberts), a any elk tag for Wyoming (Going to use my 7mm-08), a deer tag for rifle in ND (My 7mm-08), a deer bow tag in ND (Probably going to use my bow ), and a cow elk tag in Colorado (My 7mm-08). And my Dad has all the same tags as me except for the cow elk tag in Colorado. Should be a fun year!
), and a cow elk tag in Colorado (My 7mm-08). And my Dad has all the same tags as me except for the cow elk tag in Colorado. Should be a fun year!For what it's worth, there's more error in scope internal adjustment movement per click that most folks realize. One reason is the focal length of all the lens elements aren't exact to specs; they can easily vary 5%. Add them all up and 'tis easy to get more than a 5% error per click. The other reason's the mechanics are made close to exact specs stated, but they ain't exact for the distance between the adjustment contact point and where the lens tube pivots in the scope.
One needs to see exactly what their scope moves the reticule per click for reliable adjustments for range changes. And moving a few-shot group around a target ain't all that accurate unless you can shoot your rifle and its ammo into sub 1/10th MOA at 100 yards. Instead, put up a ruler at a known distance then clamp the scoped rifle in something to hold it scope steady on the ruler. Move the scope 10 major units (MOA, mils, etc) and see how far the reticule moves in inches on the ruler. Then use grade school math to figure out exactly how much per click the reticule moved.
The only scopes that are exact are the old Lyman, Fecker, Litchert, Unertl, El Monte and Remington externally adjusted ones. With bases exactly 7.200 inches apart, their 40 tpi threaded adjustments with 50 clicks per turn moved the scope tube exactly .000500" per click at the adjustment flat; exactly 1/4 inch per hundred yards or 1/4 traditional MOA per click. Folks wanting the adjustments in trig MOA (1.0472 inch at 100 yds) would have the bases spaced at 6.875 inches.
One needs to see exactly what their scope moves the reticule per click for reliable adjustments for range changes. And moving a few-shot group around a target ain't all that accurate unless you can shoot your rifle and its ammo into sub 1/10th MOA at 100 yards. Instead, put up a ruler at a known distance then clamp the scoped rifle in something to hold it scope steady on the ruler. Move the scope 10 major units (MOA, mils, etc) and see how far the reticule moves in inches on the ruler. Then use grade school math to figure out exactly how much per click the reticule moved.
The only scopes that are exact are the old Lyman, Fecker, Litchert, Unertl, El Monte and Remington externally adjusted ones. With bases exactly 7.200 inches apart, their 40 tpi threaded adjustments with 50 clicks per turn moved the scope tube exactly .000500" per click at the adjustment flat; exactly 1/4 inch per hundred yards or 1/4 traditional MOA per click. Folks wanting the adjustments in trig MOA (1.0472 inch at 100 yds) would have the bases spaced at 6.875 inches.
Broz
Well-Known Member
Bart I think I read in a previous post where Riley had already done this.
Jeff
Jeff
Well then, he's got other issues to resolve.
Adjusting for ballistics is a nightmare. Especially when the data you have doesn't end up making the end result what you want. Finding the one error in a long list of variables can be frustrating. Been there. Done that.
Broz
Well-Known Member
I hear that. Here lately I have done several and all with their own little quirk. But my first time set up average is much better since I bought my Oehler 35.
Jeff
barnesuser28
Well-Known Member
I did check the adjustments on my scope however i dont think i did it accuratly so i am going to try it again and see what results i get. Thanks for your help you guys, i really appreciate it.
Broz is exactly right on the money for doing your own field tests and then fudging with your velocity and BC. I took my 25-06 out and field tested the 115 gr bergers. My velocity was off by about 60 fps from what my chrono said.
I wouldn't even care if it was 100 fps off if getting it right will allow me to hit the bullseye on my steel plate.
I have also moved to heavy for caliber bullets with the high BC because like Broz I believe in it and the targets showing the wind drift differences is proof enough for me.
Good luck Riley!
I wouldn't even care if it was 100 fps off if getting it right will allow me to hit the bullseye on my steel plate.
I have also moved to heavy for caliber bullets with the high BC because like Broz I believe in it and the targets showing the wind drift differences is proof enough for me.
Good luck Riley!
How'd you figure the velocity was about 60 fps off?
My chrono was reading around 3050 to 3060 fps but when I put that velocity into Shooter it wasn't giving me the right amount of drop out to the ranges that I was shooting. I had to lower the velocity in shooter to I believe it was 3000 fps to match the drop in elevation that I was getting from the field testing.I can't prove that the chrono was wrong but when I changed the velocity in shooter it got me right on all the way out to 700 yds. Maybe Im working with shooter in the wrong way but who knows.
Differences in atmospheric conditions between what Shooter used and what existed where you shot could easily have made that difference.
Most chronographs set up properly are typically accurate to within 5 fps of reality. But ones shooting position can easily give a 60 fps spread across different ones.
