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AR-15 Rifle Scope 4 X 32 Bore Sighting How To ?

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AR-15 Rifle Scope 4 X 32 Bore Sighting How To ?

Postby rong on Sun Oct 26, 2008 9:53 am

Just purchased the OLD SCHOOL top of carry handle mount 4 X 32 Scope for my M-4. Went to the range to have it bore sighted. They looked at me like I was nuts, state, OH, it is too tall of a mount. Does anybody know who or how? Does Lyman have an adapter I could purchase for bore sighting this type of mount? There has to be some way, hell this scope was used for years on Ar-15's and M-16's in the military. After 40 rounds I gave up at the range, could not print the paper at 25 yards. Please help!

Thanks,
Ron in Houston
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Postby Steven_L on Mon Oct 27, 2008 4:18 pm

A collimating boresighter with an extension will work, I've used them for years. Brownell's should carry them. Otherwise use a laser boresighter.

The old school way is to open your gun and look down the bore. Adjust so you can see a distant bullseye down your barrel, then move your scope turrets to approximately the same place. Get on the paper and adjust at a longer distance.

If you couln't even hit a large piece of paper at 25 yards with 40 rounds, something else is wrong.
Aim Hard!

Steve at OpticsPlanet
http://www.opticsplanet.net

Phone: (800) 504-5897
Fax: (847) 919-3003
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Re: AR-15 Rifle Scope 4 X 32 Bore Sighting How To ?

Postby BlkRflsRok on Thu Apr 21, 2011 10:20 pm

How would one stare down the barrel of an AR semi-auto platform and use the old fashioned bolt action method you described? You'd have to remove the upper, put it on a vice with a block to keep it still while adjusting the scope on the uppper recvr. at the range? Seriously. I'm not trying to be a jerk. I'm wondering how you would do it at a range. Also, any opinions on the Leuopold magnetic boresighter (Zero Point Magnetic Illuminated Boresighter)? I can't figure out how to correctly place the thing on my birdcage flash hider. I have a 'chamber based' laser boresighter but I'm not psyched about the results I've got w/ it.
Thanks in advance...
BlkRflsRok
 

Re: AR-15 Rifle Scope 4 X 32 Bore Sighting How To ?

Postby farmgunsMO on Fri May 06, 2011 8:25 am

I had issues with mounting a 4-12 varmit scope on the AR-15 HBar Target on the handle (permanent handle). It would pattern super at 25 yards but not be on the paper at 100 at all. Being a neophite on angular intercept of the bore, I called Hornady Ammuntion, Tech support, they calculated for me, because the scope center is 3.5 inches above the bore center, with the 20 inch barrel and 1 / 7 twist, to sight my AR in at 100, from its current adjustment would mean dropping the cross hairs by 36 clicks (1/4 inch at 100 yards). That means I will be 2.25 inches low at 25 yards and spot on at 100. Right now I was 9 inches high and shooting over the target at 100. Most of my varmit shooting here on the farm is 100 to 200 yards so I will now check it at 200. I used PVC to make a 200 yard target frame I could easily see at 200. Recommended ammo for me is the Hornady 53gr .223 Vmax if you are serious about coyotes. The AR is an awesome varmit rifle.

I also purchased a Sitelite SL-100 Mag Laser bore sighter which can do all calibers and shotguns and includes a scope leveling adapter. It includes ballistic target software to print a calibrated laser target but I wanted to know why as well as just bore sight it.
farmgunsMO
 

Re: AR-15 Rifle Scope 4 X 32 Bore Sighting How To ?

Postby helimech4565 on Wed Jun 22, 2011 9:15 am

It's an annoying fact of physics that the farther your sights/scope are away from the centerline of the bore, the more adjustments you will have to make when you shoot at anything that isn't exactly at whatever range you zeroed your weapon. On top of that, it's all cumulative, i.e. high rings plus long range equals big math and LOTS of clicks to get your reticle and the bore to intersect when you want them to. This is why it can be helpful to (1) get the lowest mount/shortest rings you can get away with, and (2) zero at whatever distance you think is most likely you'll be shooting at.....

In the end an AR platform in .223 or 5.56 with a 16 to 20 inch barrel and a shortish zero (say 50m to 100m) is going to be pretty cooperative out to 300m to 400m with iron sights for most shooters. When you start aiming for 500m to 600m; ranges where most people are really going to start wanting a scope or other optic, you need to start looking at principles, techniques, and equipment that long range shooters are using. Especially when realize that the small and light .223/5.56 can start getting erratic at longer distances anyhow.

My advice; if you want to mount a scope on your AR and shoot at longer ranges; rather that messing with carry handle mounts, get a flat-top receiver. They're not terribly expensive or hard to swap out and you'll be MUCH happier with the end result. Good luck!
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