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What Variable to change Wen truing my Weapon at Extended Ranges

 
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  #1  
Old 12-23-2013, 11:42 PM
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What Variable to change Wen truing my Weapon at Extended Ranges

When doing the truing process I have heard different opinions. Some say after sighting the gun in at 100y then shooting out at 900-1300y or whatever range you can consistently hit targets at, if the group is high or low to adjust the MV. Some say if I have Chronograph the gun and feel confident in the MV that I should change the BC. By the way Iím shooting the 230 Target Hybrids. Some people lean toward changing the MV over the BC when truing a weapon or vice versa. So my question is, if I do a good chrono of a weapon and take as many variables as I can out of the inputs I put into my Kestrel Atrag, which one should I change when truing the weapon to match the scope value?

Thanks,
Joden
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Old 12-24-2013, 03:10 AM
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Re: What Variable to change Wen truing my Weapon at Extended Ranges

It may well take a little of both.

If you are fine tuning, which is clay birds to beyond 1K, you'll find your muzzle velocity will not be what your chony says it is and your bc will not be what is published.

Different barrels have slightly different bc values so if you and your buddy are shooting the same bullet in the same cartridge using the same bc will get you close but is that close enough?

Another input to be concerned with is the difference between line of bore and line of sight that is, sight height. If your scope base isn't canted this can be measured. If canted, measure then calculate the fudge factor.

Bringing at least these things into alignment will get you where you want to be.
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  #3  
Old 12-24-2013, 10:00 AM
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Re: What Variable to change Wen truing my Weapon at Extended Ranges

Great, thanks for the clarity Roy. I mess around with both.
Joden
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Old 12-24-2013, 10:03 AM
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Re: What Variable to change Wen truing my Weapon at Extended Ranges

I have seen folks tweak their systems trying to make sense of the trajectory and their programing so that the adjustments and point of impacts actually work. But they either end up with a velocity that is not true or they think the BC is better than what it’s rated at.

Just something I check on any new scope, doesn’t matter what mfg. before or while mounted on the rifle.

I have an area that has been marked with a true measured 100 yards, using a 100’ tape not a laser. Then I hang a 72” carpenter’s rule that has been checked with a caliper for true readings. Sounds dumb but you would be surprised how some rules of this type are off a bunch by the time you get to 72” kinda like some scope travels as fallows.

Make sure the rule is hung or mounted true vertical with a level.
You can also take a fine point Sharpie and mark all the mil settings using your caliper, so you’re ready for moa or mil reticles for testing.
The most time consuming part is setting up the first time.

Now that you have the range measured and the carpenters rule checked, marked and hung true vertical, you can either take a piece of steel square stock equipped with a picatinny rail held in a vise solid ready to mount the rings and scope on or a solid gun vise of some sort for securing the complete rifle. I like the solid piece of steel stock for clamping down tight in the vise to eliminate any chance of movement with the scope.

Whatever method used, secure the scope or rifle equipped with the scope while having the scope reticle aiming at the top edge of the rule while set at zero.

Now turn your elevation turret and make notes as to how much every click of the turret moves on the rule. (In some cases another person with a pointer down by the rule and using radios will be helpful)l. As you adjust your scope’s elevation turret pay attention to the error. Try this a few times to make sure your still at zero when dialing back up to the top of the rule in case your scope or gun may have moved while testing – it’s all about good info

You will see any amount of error really start to add up as you get to your max travel or 72” on the rule. Take the info you have and check with your ballistics program to change the value of your clicks in your scope info you entered into the program,

Cause for all this is the tolerances in the machining of the threads and or wear in the turret travel.
I have seen some dumbfounded looks while doing this quick exercise, it’s nice to know that when you dial in 10 or 25 mils that you really do have 10 or 25 mils not 11.5 or 28. Same goes for folks with moa adjustments a 1/4 moa is a true 1/4 moa or 10 moa's when dialed.

This simple test cleans up questionable speeds and BCs and helps with making drop charts that are true as far as corrections needed.

Another thing as long as the level bubble on the scope or rifle is true, you should be able to dial the full vertical travel adjustment and travel down the rule without veering off course some, if it does move your turret/scope reticle is not plumb with gravity.

It’s all the little things that add up and make a big difference in time.

I do get a little long winded at times

Cheers
oneshot.onehit
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  #5  
Old 12-24-2013, 12:36 PM
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Re: What Variable to change Wen truing my Weapon at Extended Ranges

All great info, thanks for the tips
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  #6  
Old 04-27-2014, 01:17 PM
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Re: What Variable to change Wen truing my Weapon at Extended Ranges

Quote:
Originally Posted by royinidaho View Post
It may well take a little of both.

If you are fine tuning, which is clay birds to beyond 1K, you'll find your muzzle velocity will not be what your chony says it is and your bc will not be what is published.

Different barrels have slightly different bc values so if you and your buddy are shooting the same bullet in the same cartridge using the same bc will get you close but is that close enough?

Another input to be concerned with is the difference between line of bore and line of sight that is, sight height. If your scope base isn't canted this can be measured. If canted, measure then calculate the fudge factor.

Bringing at least these things into alignment will get you where you want to be.
Roy-

I know that this is an old post, but I hope you could still answer a question. If the scope base is canted, which part do you measure to, and what is the fudge factor you refer to?
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  #7  
Old 04-27-2014, 08:17 PM
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Re: What Variable to change Wen truing my Weapon at Extended Ranges

Another input to be concerned with is the difference between line of bore and line of sight that is, sight height. If your scope base isn't canted this can be measured. If canted, measure then calculate the fudge factor.

Bringing at least these things into alignment will get you where you want to be.[/QUOTE]



Im curious about this too. For example, I have a 20MOA base, are you saying that I need to measure from the front of the scope for proper scope height or from the middle of the scope. I would think the front but could be wrong.

Joden
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