Well I am new to ar’s and I ended up purchasing a blackthorne kit. After reading some of the posts I see it may not of been the best decison. Anyway It is a 16" a3 flattop m4, with a Bang Arms lower, and a carry handle from blackthorne. The gun went together fairly easy and everything seems to work fine but It shoots 6-8" low at fifty yards. I read the faq for zeroing in iron sights and I have the front post all the way down. When I turn the rear sight all the way up it shoots pretty close but I know It is supposed to be bottomed out at fifty to 200. I was just wondering if there is anything I should check for this problem? Maybe a better quality carry handle? Or anything to look for with the upper? I was shooting remington 55 fmj ammo.
There are others that post here that know more than me.
But I’d say you have the wrong front sight assembly for the flat top. They are a bit shorter on the flat top ARs.
You need to adjust your from sight post down further.
Also adjust your rear sight so it’s bottoming out 4 clicks below 6/3 if you have an A2 type rear sight.
The rear sight I have doesn’t say 6/3 it has numbers like 1 thru 15. The front sight post is adjusted down as far as it will go. I don’t know if this means much but on the side of the front sight it looks like there is a “s” cast into it.
If you can try again at 25yds and try for 1" low. Then check at 50yds. Sounds like one of the very cheap Chinese carry handles. If you can I’d get a either a RRA or Bushmaster one since you more than likely have a rifle height FSB.
The first time I went out and shot I was shooting at 25 yards and It was still low. I thought it was due to the cheap wolf ammo, so I went home and cleaned the gun and tried again but at 50 yards. same thing. The carry handle does feel very cheap. What is my fsb supposed to measure? I will try to get a better quality carry handle next week. I hope that cures the problem.
I knew one of you guys had that pic.
I just ran down stairs to measure mine. I have a BM A2 carbine and a RRA mid-length flat top and they are right on those measurements.
I measured my FSB and came up with 1.947. so it has the standard FSB. and that shoot make my flattop shoot high, right?
Usually it’ll require a taller front sight post like this one from Bushmaster for $5.50
If you use the one thats in your FSB it’ll probably require that to zero at 50yds your front sight post will be nearly falling out of the FSB.
Also remember that moving the front sight up makes the group go down. This is opposite what the rear does where moving the rear sight left makes the group go left. When doing the 50yds zero the rear sight elevation is bottomed out like I said earlier 6/3 -4 clicks (4 clicks lower than it’s lowest marked setting). The rear sight usually requires a 1/16" allen wrench to allow it to do this. During zeroing the only elevation changes are made at the front sight and windage is at the rear sight.
This is complete directions for the Santose 50yd Zero.
I second that. Zero the carbine with the rear sight set properly so you can set it to different ranges and still hit without using Kentucky windage.
So I’ve got a question. My rifle is doing the same thing and when I tried to bottom out the rear sight, the 1/16" wrench wouldn’t fit. And my front sight isn’t F marked. I finally sighted it in at 30 yrds for minute of man, but my rear sight’s at 4 clicks after 4.
I have tried the 50 yard zero technique and that is why I don’t understand why it shoots low with the standard FSB and the front post turned all the way down. It shoot be shooting very high. Can my rear sight be that far off? Is there a standard measurement for the a2 carry handle on the a3 receiver?
I feel like a idiot now. I figured out my problem. Come to find out my front sight post had a lot more room to go down. So I finally have it shooting correct. I have one more question. My carry handle rear windage adjustment knob is labeled 1 thru 20. So do I just bottom it out at 0 and then zero the gun at 50y? And after zeroing it does it mean if I turn the windage adjustment to 5 = 500yards 10= 1000? Thanks for all your guy’s help
If it were me I’d just replace that who knows who’s it is carry handle with either a Colt one (or better yet, a fixed rear sight like the LaRue BUIS) and install a taller .040" front sight post. You really don’t need a 6-800yd rear sight on an AR15 (just my opinion).
Bottom out the “windage” knob?
Windage controls affect the horizontal position of the rear peep sight. The sight should be centered at the beginning of the zeroing process. Then the windage knob turned to move the point of impact left or right so that it coincides with the point of aim.
Yes
And after zeroing it does it mean if I turn the windage adjustment to 5 = 500yards 10= 1000? Thanks for all your guy’s help
No, the numbers are equal to the number of ‘clicks’ not to any particular range. This kind of elevation wheel is more generic, like the elevation knobs on scopes.
My 2 Bushmaster shot WAY low from Factory!
and had the crank it FSB all the way 
My LMTs are just fine and my BUISS Need no L or R adjustments
I hate A2 sights also