40yd zero for 100yd

demolition101 · #1 05-16-2011, 07:41 PM

If I want my rifle zero'd at 100yd but only have access to a 40yd range how high does it need to be? I shoot a .308 Norinco M305 and I put 180gr federal powershock through it. Thanks

demolition101 · #2 05-16-2011, 07:50 PM

If I am correct in assuming so, ballistic charts say I should be -1.1'' at 40yd if zero'd at 100yd. So am I correct in assuming then that if I zero the round 1.1'' above the bullseye at 40yd I should be relatively zero'd at 100yd?

Lefty-Canuck · #3 05-16-2011, 07:53 PM

Not necessarily....you actually have to measure and account for the height above bore of the crosshairs inorder to calculate this as well AND you need to know the muzzle velocity...measured...not approximate.

Lefty

demolition101 · #4 05-16-2011, 07:55 PM

ruining my night lefty lol. Don't suppose you can explain how to do that over this? Thinking of using the phoenix gun range but they only have a 40yd range.

Lefty-Canuck · #5 05-16-2011, 07:57 PM

Send me approximate muzzle velocity and I will try to calc it for you...then you can let me know how I did! lol

Lefty

demolition101 · #6 05-16-2011, 07:59 PM

Quote:

Originally Posted by Lefty-Canuck

Send me approximate muzzle velocity and I will try to calc it for you...then you can let me know how I did! lol

Lefty

It's saying 2570fps

demolition101 · #7 05-16-2011, 08:00 PM

How do you calculate it? I am curious as to the method.

Lefty-Canuck · #8 05-16-2011, 08:01 PM

Using a bullet BC of 0.400, muzzle velocity of 2600, scope height from bore of 1.50 inches, temp of 70 deg C, and altitude of 2000.

I get 0.25 inches low at 40 yards for a 100 yrd zero....

Lefty

demolition101 · #9 05-16-2011, 08:03 PM

My scope height is 3'' from bore center to scope center. Why is there such a big difference between the -1.1'' and the .25'' you explained?

Lefty-Canuck · #10 05-16-2011, 08:24 PM

Well with a 3 inch difference instead of a 1.5 inch one the 40 yards zero is just as you calc'd at -1.14 inch. As you can see at close distances the scope height over bore makes a difference.

So at a dead center aim at 40 yrds your POI should be -1.1 inches from aim point, if you want a 100yrds zero....asuming we have the BC and velocity values correct.

Lefty

demolition101 · #11 05-16-2011, 08:26 PM

Great thanks for the help. Ill let you know if We're right. Know any good 100m-300m ranges near Edmonton?

Lefty-Canuck · #12 05-16-2011, 08:27 PM

I used to..... but now I shoot at a friends farm, can't go wrong with Sherwood Park from what I understand.

Lefty

300savage · #13 05-16-2011, 09:05 PM

180's are hard on the m305/m14 action. If you put alot of the heavy pills through it, your action will take an awful beating. 165's are what is recommended.

Okotokian · #14 05-17-2011, 03:49 PM

Take it to a field, pace off a hundred years, have an enjoyable time, get some practice in too.

hal53 · #15 05-17-2011, 04:09 PM

Quote:

Originally Posted by Okotokian

Take it to a field, pace off a hundred years, have an enjoyable time, get some practice in too.

I gotta walk 100 years ???...just to sight in my rifle!!!!???....LOL!!!!!!

Okotokian · #16 05-17-2011, 04:14 PM

Quote:

Originally Posted by hal53

I gotta walk 100 years ???...just to sight in my rifle!!!!???....LOL!!!!!!

LOL oh boy.... it only seems like a 100 years sometimes

100 YARDS.... thank you.

ACKLEY ABE · #17 05-17-2011, 04:22 PM

FYI Phoenix is shorter than 40 yards

solocam · #18 05-17-2011, 05:15 PM

308. is about -0.24 to -0.26 at 40 yards 100 yards zero. in your 180gr.

savage shooter · #19 05-17-2011, 05:38 PM

Quote:

Originally Posted by ACKLEY ABE

FYI Phoenix is shorter than 40 yards

Phoenix claims it's 40 yards. I go there all the time. What do you base your assertion on? I'd love to know.

Tundra Monkey · #20 05-17-2011, 06:17 PM

Quote:

Originally Posted by Okotokian

LOL oh boy.... it only seems like a 100 years sometimes

There is some truth in that Oko for sure!!!!!!!

tm

ACKLEY ABE · #21 05-18-2011, 07:46 AM

Quote:

Originally Posted by savage shooter

Phoenix claims it's 40 yards. I go there all the time. What do you base your assertion on? I'd love to know.

My ASSeration is based on working there part time years ago when Bob Prestash owned it and shooting in it several hundred times while I was there. Measure it. If you are trying to do calcs. you need to know the exact length which is why I ended up measuring it. It was common knowledge at the time that it wasn't 40. By the way the overpass on 50th is 293 yards from the front door. I think the range is 37 if I remember correctly but it might even be shorter, unless the have moved the shooting positions back through the door or moved the butts back to the overhead door behind them. Three yards difference isn't much but it does make a difference.

Get back to me, they may have changed it, but even back then everbody "thought" it was fourty.

Sorta like Spruce Grove Gun Club. The Hundred yard butt on Rifle 2 is not, nor is it a hundred metres.

ACKLEY ABE · #22 05-18-2011, 07:50 AM

Quote:

Originally Posted by Lefty-Canuck

Using a bullet BC of 0.400, muzzle velocity of 2600, scope height from bore of 1.50 inches, temp of 70 deg C, and altitude of 2000.

I get 0.25 inches low at 40 yards for a 100 yrd zero....

Lefty

Yo Lefty, I'm pretty sure you mean 70 deg F. 70C is 158F.

savage shooter · #23 05-18-2011, 08:30 AM

Quote:

Originally Posted by ACKLEY ABE

My ASSeration is based on working there part time years ago when Bob Prestash owned it and shooting in it several hundred times while I was there. Measure it. If you are trying to do calcs. you need to know the exact length which is why I ended up measuring it. It was common knowledge at the time that it wasn't 40. By the way the overpass on 50th is 293 yards from the front door. I think the range is 37 if I remember correctly but it might even be shorter, unless the have moved the shooting positions back through the door or moved the butts back to the overhead door behind them. Three yards difference isn't much but it does make a difference.

Get back to me, they may have changed it, but even back then everbody "thought" it was fourty.

Sorta like Spruce Grove Gun Club. The Hundred yard butt on Rifle 2 is not, nor is it a hundred metres.

Hmmm...having not seen it back then I'm not sure if it's changed. I will have to bring my laser range finder with me next time I go and report back.

ACKLEY ABE · #24 05-18-2011, 08:34 AM

Quote:

Originally Posted by ACKLEY ABE

My ASSeration is based on working there part time years ago when Bob Prestash owned it and shooting in it several hundred times while I was there. Measure it. If you are trying to do calcs. you need to know the exact length which is why I ended up measuring it. It was common knowledge at the time that it wasn't 40. By the way the overpass on 50th is 293 yards from the front door. I think the range is 37 if I remember correctly but it might even be shorter, unless the have moved the shooting positions back through the door or moved the butts back to the overhead door behind them. Three yards difference isn't much but it does make a difference.

Get back to me, they may have changed it, but even back then everbody "thought" it was fourty.

Sorta like Spruce Grove Gun Club. The Hundred yard butt on Rifle 2 is not, nor is it a hundred metres.

ooops.... sorry for the typo asserstion...of course.

HunterRed · #25 05-18-2011, 08:42 AM

Quote:

Originally Posted by hal53

I gotta walk 100 years ???...just to sight in my rifle!!!!???....LOL!!!!!!

actually you gotta walk 200 unless you plan on pinning the target to the side of the truck! 100 out and 100 back.

Lefty-Canuck · #26 05-18-2011, 09:58 AM

Quote:

Originally Posted by ACKLEY ABE

Yo Lefty, I'm pretty sure you mean 70 deg F. 70C is 158F.

You are correct sir!

Lefty