Home Forums Hunting & Shooting Hunting Optics Informative Post

This was posted by JonA here, http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1714859&page=all



I won't press you too hard for the brands, but in case you're wondering that is pretty bad. The high end scopes I've measured have all fallen within +/-1% error. In fact, when they're that close they rival the accuracy of your measurement methods, so I figure that's about as good as one can expect. But with the amount of money the top end scopes cost, I do expect that accuracy from them. I paid for it dammit! With mid-level scopes I figure +/- 2% is about all you can expect. There's a reason they're cheaper. For cheap stuff, it's anybody's guess.

In other words, I hope you didn't pay too much for those scopes. If you did, I'd be sending some back.

Regardless, thanks for posting and bringing awareness to the issue. As a technical-type person, it sometimes confounds me why so many shooters do anything to avoid doing anything so technical such as measuring. A couple years ago I posted here how I measured my Falcon and found it was around 2% off IIRC. It's like I was from Mars or speaking a different language or something.

Originally Posted By: Switchblade
I do need to ask:
Why are you measuring 36" at 100M? You should only need 6MOA or 6" at 100M to test on a 1" circle or a 1/2" circle.

Because your rifle isn't accurate enough to discern a small percentage error in the click value by measuring over such a small distance. If your clicks were 2% off, that would put them less than 1/8" off over 6" so your rifle would need to be insanely accurate to even notice such a deviation, much less measure it accurately. Over 36", the same error will be 3/4" which is pretty easily seen with a good rifle.

10 Mils is a good standard as most scopes have that much adjustment and the math is easy. If it takes 105 clicks to go 10 mils, you're 5% off. If it takes 98 clicks, you're 2% off. You can then enter that value in programs such as JBM and adjust your drop charts accordingly. You'll find this gives much better results than what most people do--screw with the BC of the bullet in the program until it matches the incorrect adjustment of their scope such that two wrongs is making a right. Change distances or conditions significantly and the two wrongs don't make a right anymore, leading people to blame the ballistics program can't be trusted when the problem really is with their equipment.

For scopes with enough adjustment, going 15 or 20 mils is great and makes it easier to see any error. At the very least one can measure 10 mils at different spots in the range of adjustment to make sure it's consistent.

My preference is to remove the rifle's accuracy from the equation all together by using a collimator to do the measurements. Not only can you measure click value and reticle subtension that way, but also find things like dead clicks at the end of the adjustment range, reticles canted with respect to the erector's adjustments, reticles that stick and jump instead of moving smoothly, etc. You can know more about a new scope before you ever fire a shot than most people will ever know about their scopes as long as they own them as far as the precision of their adjustments go.

I say zero it and go hunt. In the Army, we called this "Pole vaulting over Rat turds..."

That is a fine idea as long as one is not useing the turrets to adjust for trajectory compensation at long range in the field. If one is using the turrets for elevation correction then JonA's post is extremely informative

The only turrets I need are between my ears.

I am not what is currently defined as a "long range" shooter or hunter....but if I decided to be one,I would be pretty darn fussy about the accuracy, precision,and repeatability of my turrets.

This makes sense to me because margins of error can compound at distance.So I would want things as tight as I could get them.

This is why an old timer I knew always recommended that folks begin testing at 200 yards. This is where you can just begin to deconvolute scope from rifle and rifle from bullet stability. 400 yards is better if its a calm day or a steady breeze.

I like it.

The one thing I do is zero my rifle at 250 yards instead of 100 yards and call it good. I'm a hunter and not a long range marksman either. No twisting and fiddling for me.

It is good solid info in the post though.

fish head