proper sight hight with tapered bases

Russ M · #1 01-21-2009, 01:08 AM

when you have tapered bases what is the proper way of measureing sight hight with tapered bases. i am using the leupold bore sighter, at first i had strait bases on my gun and the leupold bore sighter put me with in a couple of inches of bulls eye then after in stalling my tapered bases i used the same procedure (1/2 out side of objective + hight above bore + 1/2 barrel directly under objective), what i am wondering is if i should use thous numbers and knowing my bases are 20 moa to take the hight above the bore at the center of the scope ?
thank you for your input
p.s. i wasn't sure were to start this thread so i thought this is were most people look, for the future were should a thread like this go?

jmason · #2 01-21-2009, 10:52 AM

Russ I'm far from an expert but I think your procedure is sound.

Buffalobob · #3 01-21-2009, 06:38 PM

Depending on whether it is a long action or a short action it takes about 0.001 inches to give 1 MOA, IIRC. So if you have a 20 MOA base you would have a difference of 0.02inches between the front and rear of the base. In my way of thinking, I am not going to lose any sleep over this trivial of a number

Somewhere back in the far crevices of this forum, I have exactly calculated this number as has a guy named ABINOK.

A good place to put optics questions is the Optics forum or in the case of this question it could have been the Ballistics part.

Russ M · #4 01-22-2009, 01:06 AM

yes that is true that over the action it is a small amount but then when you take that same angle and go over the distance of the barrel i have a 26" so lets use that number the difference now becomes .145" and because of the bore siter i am using that is enuf to put me out at 100 yards by 7 " atleast that was my result

Buffalobob · #5 01-22-2009, 06:36 AM

Well, that's true. I did not understand the real question you were asking.

In general terms, 1.0 MOA is 0.000278 inches per inch so at 26 inches with a 20 MOA base you would have been off by 0.145 inches at the end of the barrel.

Russ M · #6 01-22-2009, 04:36 PM

yes i seem to have that problem of not being able to put things in to words so that other can compeletly under stand what i am trying to say and i guess i answered my own question while i was at it. thank you for your input, do you think that that little bit might afect how much a ballistic computer will tell you to adjust or in that case is it just a minute amount not to worry about

Buffalobob · #7 01-22-2009, 04:50 PM

Depending upon many things such as velocity and BC, but just as a reference point--- 0.1 inch error in scope height gives you a 1 inch error in bullet impact at 1000 yards. If you use real drop data to calibrate your ballistic computation then the error becomes smaller and may be at a different point. In other words, I try to fit my drops more carefully at the longer ranges than the short ranges, so I would tend to make the problem even smaller just by using real data.