View Full Version : Running out of Iron Sight Adjustment before zero is achieved.
danieljmaunder
11-23-15, 15:35
Hey Guys,
Was teaching a class this past Saturday and at the beginning of each course we make sure all students have a 50 yd zero on their carbines. I had one student that could not achieve zero because his rear sight ran out of adjustment. He was about 4 inches left of center and the rear aperature was cranked all the way to the right. He custom built the upper himself and I'll list the specs below.
BCM Flat top upper
Weapon Outfitters 13.7 BA Hanson Bbl
PRI Mk12 Handguard
Surefire Socom Brake
Troy Industries front and rear buis.
I'm thinking that because the front sight is mounted on the rail, when he cranked down the barrel but that it's misaligned so when the handguard was installed it is not aligned concentric to the center of the upper. That's my guess as the front sight appears canted to the right slightly.
Any insight is appreciated as I have yet to see this one in a class before.
Moose
His rail was crooked or canted.
On that handguard the picatinny rail does not meet the upper. You need to use a straightedge to verify it is clocked correctly.
Auto-X Fil
11-23-15, 19:54
Who shows up to a class 8MOA off the bullseye? Do you often have people completely un-sighted-in when they arrive?
Coal Dragger
11-23-15, 21:05
Probably had the optic zeroed, and tossed on a BUIS and figured it was good enough?
Who shows up to a class 8MOA off the bullseye? Do you often have people completely un-sighted-in when they arrive? one of my friends takes lots of classes and it happens often with a new shooter.
Chunky_Lover
11-24-15, 08:07
use one of those laser line levels and run down entire top of the rifle
I use those on ak's to get the cant out of the front sights
MOLON AABE
11-24-15, 22:56
Happens all the time. Getting a rail properly clocked and indexed isn't hard, but alot of home builds end up being way off.
Happens all the time. Getting a rail properly clocked and indexed isn't hard, but alot of home builds end up being way off.
Correct. I've found the best way to line a rail up to the upper receiver; (at least on my Midwest Industries quad rails), is to take a removable carry handle and attached it to the receiver rail and the rail itself; half on the upper rail and half on the rail. Next, tighten it down well and then tighten the jamb nut down with the carry handle still attached. Finally I install the anti-rotation screw/pin last but don't crank it down too hard, just a hair past snug with blue locktite is sufficient. Remove the carry handle and boom; the rail is aligned as close as humanly possible.
To align newer M-Lok styled rails I align the barrel nut, gas tube, and upper receiver gas hole as close to perfect as possible. It usually takes 3-4 times of tightening, measuring, loosening, and retightening everything to get that gas tube in without binding at all on the sides of the teeth of the barrel nut while being aligned directly in the center of the receiver hole. Then I use the same process as described above with the carry handle for the final fine tune/rail alignment. It has worked every time for me with the most I've ever had to crank the rear site is 2-3 clicks in either direction to get zero'd. YMMV.
Correct. I've found the best way to line a rail up to the upper receiver; (at least on my Midwest Industries quad rails), is to take a removable carry handle and attached it to the receiver rail and the rail itself; half on the upper rail and half on the rail. Next, tighten it down well and then tighten the jamb nut down with the carry handle still attached. Finally I install the anti-rotation screw/pin last but don't crank it down too hard, just a hair past snug with blue locktite is sufficient. Remove the carry handle and boom; the rail is aligned as close as humanly possible.
To align newer M-Lok styled rails I align the barrel nut, gas tube, and upper receiver gas hole as close to perfect as possible. It usually takes 3-4 times of tightening, measuring, loosening, and retightening everything to get that gas tube in without binding at all on the sides of the teeth of the barrel nut while being aligned directly in the center of the receiver hole. Then I use the same process as described above with the carry handle for the final fine tune/rail alignment. It has worked every time for me with the most I've ever had to crank the rear site is 2-3 clicks in either direction to get zero'd. YMMV.
Did you notice what hand guard he is using? He'll have a tough time using a carry handle to clock it.
Did you notice what hand guard he is using? He'll have a tough time using a carry handle to clock it.
No, never heard of that rail. My post was meant for anyone that can use the info to align a rail that a detachable carry handle can be used on... I believe I mentioned quad rails and M-loks. If you or he cannot benefit from my post then don't use it. Others will however...
No, never heard of that rail. My post was meant for anyone that can use the info to align a rail that a detachable carry handle can be used on... I believe I mentioned quad rails and M-loks. If you or he cannot benefit from my post then don't use it. Others will however...
Thanks for the advice. If your yard needs raking I recommend getting a shovel and digging a hole... If you cannot benefit from my advice then don't use it. Others will however... Makes a lot of sense doesn't it?
MOLON AABE
11-26-15, 20:08
http://images.tapatalk-cdn.com/15/11/26/82720089faeb5c0bb5c05bf7b11bfebb.jpg
one of my friends takes lots of classes and it happens often with a new shooter.
Yep.
You'd be surprised how many people sign up for and intermediate or higher course without any experience.
The Company I worked for would contact you after registration to verify you knew how to shoot.
556BlackRifle
11-27-15, 20:47
Go to BCM's site and look at the upper your student has. LINK (http://www.bravocompanyusa.com/BCM-SPR-Mk-12-Mod-0-Bravo-BLACK-p/bcm-urg-mk12-0%20pri%20black.htm) Take a look at picure #6 and see commet below.
Optional Rail: ARMS #38 SPR Top Rail - This Rifle length SPR Straight top rail is a FULL Picatinny rail that connects the receiver to the forearm.
Hope this helps.
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