Ruger M77 .270 3X9X40 Scope trajectory QUESTION. HELP!


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SLMPDcitycop
November 8, 2007, 03:39 PM
I don't know the answer to this, and the guy at the range didn't as well. So I figured I would ask the experts on The High Road Forum.

I sighted my gun in on bullseye at 100 yards. If I shot the bullseye at 20 yards where would my shot be, high or low and how much. The same goes for 200 yards.

Thanks for your help!

Steve-O

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MDHunter
November 8, 2007, 03:48 PM
on a few factors, the type of ammo you're shooting and the bullet weight (in grains) primarily. You can check ballistics online, or if you buy factory ammo, they may provide ballistics info on the back of the box.

My best guess is that your point of impact at 20 yards would be slightly below the bullseye, since the bullet is just getting up to bullseye level at 100 yards.

Can I ask why you're dead on at 100 yards? If you sighted in to be 1-2" high at 100 yards, with a .270 you're good to at least 300 yards without aiming high or low.

Michael

rr2241tx
November 8, 2007, 03:54 PM
MV 3,000fps, 130gr SPT, 0@100yd:

20yd -0.9"
200yd -3.1"

.270 Win is usually zeroed at 150yd or 200 yd to take better advantage of the trajectory.

SLMPDcitycop
November 8, 2007, 04:05 PM
I'm shooting 150 grain soft points. The range I went to only allowed me 1 hour to shoot and when I finally got it zeroed at 100 yards, my time was up. So, if I shoot a deer at 20 yards (roughly) I should aim .9 inches high? And if I'm shooting a deer at 200 yards, I should aim 3.1 inches high? Thanks!

GCW5
November 8, 2007, 04:25 PM
If you expect to be shooting 200 yards, it would be best to go back to the rang3 and sight it in for 200 yards.

It sounds like you had trouble zeroing in. I'm guessing a new gun & scope. it's best to start with zero @ 25 yards, then move to 100. If you had trouble with your shots moving, something may be loose. If the scope was mounted when you bought the gun, then you may need to take everything apart, clean your stuff up & reassemble using some locktite on both action screws & scope bases/rings.

The .270 is a fine cartridge, I've been shooting one for near 40 years, and killed everything I've shot at. You'll be glad you have one.

Good luck!

Bartkowski
November 8, 2007, 04:40 PM
You should probably sight your gun in to be 1 or 2 inches high at 100yards if you plan on shooting 200 yards.

And if you are going to shoot a deer that is 20 yards and you are sighting in at 100, don't worry about that .9" you probably won't even remember to shoot a little high.

SLMPDcitycop
November 8, 2007, 06:02 PM
unfortunately I won't be able to make it back to the range before opening day (2 days away.) .9 of an inch shouldn't make that much of a difference for me. From my deer stand, 100 yards is the longest shot, so I posed the question of 20 yards since it was the closest shot. Thanks for all the input. I just didn't want to be off in case I saw a big buck.

skinewmexico
November 8, 2007, 07:21 PM
If you sight in 1.5 " high at 100, you can put the crosshairs on the shoulder from 0-300, and you'll still be in the kill zone. Deer have a big kill zone. If you're dead on a 100, I'd go up 6 clicks and call it good.

goalie
November 8, 2007, 07:33 PM
My .270 shoots about an inch low at 20 yards when sighted in at 100 yards.

That said, I sight my rifle in 1.5" high at 100, and I am good to go without adjusting my hold from "damn, that deer's close" all the way to 275 yards, which is further than I would ever get a shot where I hunt.

Sighted in as described, I aimed dead on and killed a doe at 127 yards with one shot (shot the stand with a rangefinder from the downed deer) and a 9 point buck at what couldn't have been more than 15-20 yards, also with one shot. (I didn't bother to use the laser rangefinder after that shot)

Sight in your .270 correctly, and you will have the ability to aim and shoot without correction for range out to about 300 yards. It allows you to take advantage of the flat trajectory of your fast-flying projectile and concentrate completely on the shot.

SLMPDcitycop
November 8, 2007, 08:05 PM
See, this is where I get lost. Ok, my gun is sighted in dead on 100 yards. So I go up 6 clicks which would make me 1.5 inches high at 100 yards. Now by my calculations, this would make me zeroed in exactly at 25 yards right? How are you guys figuring this out?

Steve
:confused:

goalie
November 8, 2007, 09:27 PM
The scope is above the bore of the rifle. It takes distance for the bullet to raise up even to the axis of the scope from the axis of the bore, where it started.

Think of the bullet flight as an arc, not a straight line.

http://www.chuckhawks.com/rifle_trajectory_table.htm

goalie
November 8, 2007, 09:30 PM
How are you guys figuring this out?

Honestly? I shoot my hunting rifle at 25 yards, then at 50 yards, then at 100 yards, then at 200 yards, then at 300 yards.

If possible, I shoot at 150 and 250.

I write down my point of impact for each distance in relation to a dead-on point of aim.

If you want to know your rifle, you have to shoot it. A lot.

Bwana John
November 9, 2007, 06:51 AM
Actually to be right on you need to know the height of the scope above the bore, and the precise velocity and ballistic coefficent of the projectile.

Skip work, hit the range again, go for a ~25/200 yd zero.

Put the crosshairs where they should be (heart/lung,~10" diameter), and pull the trigger, it will kill from 0-240 yds if you do your part.

Franco2shoot
November 9, 2007, 08:19 AM
Let's just take the fundementals... sight is about 2" above muzzle. Therefore a zero impact at 100 yards would seem to me to say the bullet left the muzzel, didn't start any drop for those 100 yards but actually rose to hit the center point. Over the next 100 yards the bullet would start to drop and be 1" low(based on a .308 that doesn't drop at all for the first 100 yards). If this is the trajectory... bringing the target in to 50 yards, my guess is that the rise has not completed so you should be 1" low (remember the scope is up by 2"s.. Continuing.. at 25 yards 1.5" low... and if you put the paper right in front of the muzzle 2" low...
Or did I miss somthing?

Bwana John
November 9, 2007, 08:58 AM
Therefore a zero impact at 100 yards would seem to me to say the bullet left the muzzel, didn't start any drop for those 100 yards but actually rose to hit the center point. Over the next 100 yards the bullet would start to drop and be 1" low(based on a .308 that doesn't drop at all for the first 100 yards).
You are assuming facts not in evidence.

The inflection point of the trajectory does not have to be 100 yds with a 100 yd zero.

I believe it will be above the line of sight from ~100-150 yds.(.270 Win with a 100 yd zero).

But it really dosent matter, 2" off still kills the deer.

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