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-   -   AR 15 100 yds sighting in... (http://www.firearmstalk.com/forums/f66/ar-15-100-yds-sighting-19207/)

supergus 10-16-2009 06:58 PM

AR 15 100 yds sighting in...
 
I'm trying to get my Nikon scope sighted in. Here's where I'm at right now. I think I can get better groups(this is a 2" group-10 shots) but I have to figure out if I need to work on myself or the scope. BTW it's a Bushmaster 20".
http://i258.photobucket.com/albums/h...00yds002-1.jpg

Samples.32 10-16-2009 07:40 PM

It's probably you not the scope, however, just to be sure put it into a cleaning vise and shoot it from it it should keep it steadier.

supergus 10-16-2009 07:59 PM

Quote:

Originally Posted by Samples.32 (Post 174742)
It's probably you not the scope, however, just to be sure put it into a cleaning vise and shoot it from it it should keep it steadier.

Believe it or not, I was shooting off a Caldwell Lead Slead earlier, and I actually got better groups shooting off sandbags:confused:

Samples.32 10-16-2009 09:19 PM

Quote:

Originally Posted by supergus (Post 174757)
Believe it or not, I was shooting off a Caldwell Lead Slead earlier, and I actually got better groups shooting off sandbags:confused:

That is strange :confused: no nicks on the crown is there?

Gatekeeper 10-17-2009 12:14 AM

What type of ammo? I would think 2" with cheap ammo would be decent results from a standard AR.
If its match ammo and rifle maybe your rifle likes heavier or lighter bullets.
What twist rate is your bushy?
Was there a strong cross wind?
You got 7shots in a nice 1.25" cluster then 3 high left, were they your last shots of the group?
If so it could be your barrel started to heat up causing group shift during the 10shot string.

supergus 10-17-2009 04:10 AM

Quote:

Originally Posted by Gatekeeper (Post 174872)
What type of ammo? I would think 2" with cheap ammo would be decent results from a standard AR.
If its match ammo and rifle maybe your rifle likes heavier or lighter bullets.
What twist rate is your bushy?
Was there a strong cross wind?
You got 7shots in a nice 1.25" cluster then 3 high left, were they your last shots of the group?
If so it could be your barrel started to heat up causing group shift during the 10shot string.

I was using Hornady 75 gr. match in a 1:7 barrel. Just a slight variable breeze.
As far as the groups go, I admit I didn't notice which ones were which.
I was shooting 10 rounds at a time, with a couple of minutes in between groups, so I hope the barrel didn't heat up that much. BTW I was using a 5 round magazine, so I had some downtime between mag reloads.
I'm just afraid to mess with the scope if it's really just me:o

mrm14 10-17-2009 06:06 AM

Put some flags up to judge the speed and direction of wind. Three to five will do for 100 yards. Read the wind when you are shooting first and only shoot when the flags are showing the same movement and direction from your first shots. This can reduce windage issues form your practice shots through your follolwing shots.

The range I go to has unpredictable direction and high gust winds on a regular basis and this practice helps alot. I learned this form the bench guys/gals.

supergus 10-18-2009 04:03 AM

Quote:

Originally Posted by mrm14 (Post 174982)
Put some flags up to judge the speed and direction of wind. Three to five will do for 100 yards. Read the wind when you are shooting first and only shoot when the flags are showing the same movement and direction from your first shots. This can reduce windage issues form your practice shots through your follolwing shots.

The range I go to has unpredictable direction and high gust winds on a regular basis and this practice helps alot. I learned this form the bench guys/gals.

Good suggestion; thanks a bunch:)

dangezy 10-20-2009 10:44 PM

I have an ar just like yourself and what you need to do is sight it in without the scope first. Use site black (black spray paint) on the front site post, just a little and shoot from 50 feet from a very tight loop sling my preference. Most important smooth slow trigger squeeze, focus on the front site post and relax and take two normal relaxed breaths and shoot. I would shoot 3 round groups at a time that way you could find out if its trigger jerk or your sights. If your shooting a very tight group you need to adjust your scope. semper fidelis

willfully armed 10-21-2009 06:14 AM

Paramount in sighting a gun, is understanding that point of impact changes as the barrel heats up. Shot 1 will never be the same as shot 5 or 10.

Getting it sighted in "knats ass" on a hot barrel, will not yield expected point of impact on a cold barrel.

When sighting my guns, its always 3 targets, side by side. From left to right- one shot each. Then allow the gun to cool. Repeat 3-5 times. This allows the utmost consistencies in different stages of barrel temp. You will learn the deviation from shot to shot.

My old 7mag would be a full inch deviation from hot to cold.

If you wish to have the very best chance of proper sighting, this is the widely accepted method of doing it. A good bull barrel carbine length ar CAN be exact at distances up to 500+ yards. This would not be a logical method of sighting in your old 30-30 if your only shooting at 100 yards targets, as the standard deviation is moot.


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