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M15A4 shooting way to the right at 25 meters
4/17/2012 3:32:58 PM
so im attempting to zero my m15A4 at 25 meters im in the prone theres no wind and im a former marine with a expert rifle range qualifacation. I was getting very nice groups even getting some keyholes but it was still shooting about 6 or 7 inches to the right of P.O.A. after all was said and done and i had my sights adjusted my rear sight was adjusted pretty far to the left. its pretty annoying having to adjust my cheek weld that much to get proper sight picture but its something i guess i could deal with. Are the sights on these rifles just not so good? do i maybe have them tightened down too much? or am i just doing something wrong? Any feedback would be much appreciated. 
4/17/2012 6:32:51 PM
I'd say too much trigger or your stockweld is off.
Is the barrel loose? If it seems like it is, it may just need tightening. Use a barrel wrench and tighten it. Hope either of these helps. Semper Fi Retired Marine, here Rifle and pistol coach Expert Shooter
from another forum, SBHshooter says try this:
Have you BZO'd the sights? If the sights aren't lined up, the gun will simply not shoot straight. Since the sights are (somewhat) rigidly fixed in relation to the barrel, the fit doesn't have much to do with hitting outside POA, that will tend to throw shots randomly and not into the same spot.
To tighten fit, you will need acetone, a set of feeler gauges, and some Acraglas Gel, and proper release agent. McGuire's wax works as well but is more work to apply. I used a chisel that I hand made in metalworking class for finishing touches, but anything suitably sharp will work
1) Break down shotgun style and clean upper and lower receiver around the rear pin hole thoroughly. Use the feeler gauges and figure about how much gap you have, get it to where you have to use a little pressure to close the rear pin, but don't bind it.
2) Coat the block where the rear pin thoroughly in release agent, along with the channel inside the lower from about an inch in front of the rear. Leave the area where the rear pin goes through free though, you want the glas to stick at the rear. From outside the receiver, coat the rear pin.
3) Mix up according to directions, along with enough black die to suitably match your metal and not have a piss-yellow mess.
4) Using a fairly fine utensil (I used popsicle stick broken in half lengthwise)put a good size dollop inside the lower receiver channel as far back as you can. Close the received on the gauges making sure they are far enough forward to not get stuck.
Once you close it, don't move it at all, if you think it is not tight enough, don't try to move the gauges forward to change the fit, the glas won't follow.
6) After the prescribed length of time remove the pin and open the receiver. At ~24 hours the glas hasn't set, but is hard enough to work with and will hold its shape. Taking a sharp chisel you can shave the hunk down to clean up the sides and get all your corners square and flat. Purely for looks at this point, for the OCD in us all.
Following those steps, you will effectively remove all play from the two halves and make the connection like a rock (if you did it right), it may actually take a week or so of work to work out some of the excess tightness.
Good thing about the gel, if you screw it up and lock both halves together, you can heat the whole thing in an oven and the bond will break.
Your sights and barrel are not exactly parallel, that is very common, and can be caused by a number of things. A short list from the very top of my head...
Sight base slightly off alignment with threads, spring pressure for the ball bearing in the front of the sight base wrong/missing, front sight base angled slightly, front ring of receiver not true, barrel trunion not true, piece of grit in between the trunion/receiver, crown cut at an angle (I've seen some terrible factory crowns), flash suppressor/threads angled or ports on the left side are closed somehow, hole in flash suppressor not centered with threads, chamber/chamber throat not indexed at start of cutting putting bullet into bore wrong, extreme curve in the bore (meaning, from where the chamber is cut, the barrel will curve over to the side and then back the other way resulting in an arc. I've not seen this in newer stuff, I think modern machining practices improve consistency greatly.)
By no means complete, but just move your sights over to the side and set your zero. Don't forget to make a mark so you know exactly where your zero is if you have to adjust windage at any time.
Is the barrel loose? If it seems like it is, it may just need tightening. Use a barrel wrench and tighten it. Hope either of these helps. Semper Fi Retired Marine, here Rifle and pistol coach Expert Shooter
from another forum, SBHshooter says try this:
Have you BZO'd the sights? If the sights aren't lined up, the gun will simply not shoot straight. Since the sights are (somewhat) rigidly fixed in relation to the barrel, the fit doesn't have much to do with hitting outside POA, that will tend to throw shots randomly and not into the same spot.
To tighten fit, you will need acetone, a set of feeler gauges, and some Acraglas Gel, and proper release agent. McGuire's wax works as well but is more work to apply. I used a chisel that I hand made in metalworking class for finishing touches, but anything suitably sharp will work
1) Break down shotgun style and clean upper and lower receiver around the rear pin hole thoroughly. Use the feeler gauges and figure about how much gap you have, get it to where you have to use a little pressure to close the rear pin, but don't bind it.
2) Coat the block where the rear pin thoroughly in release agent, along with the channel inside the lower from about an inch in front of the rear. Leave the area where the rear pin goes through free though, you want the glas to stick at the rear. From outside the receiver, coat the rear pin.
3) Mix up according to directions, along with enough black die to suitably match your metal and not have a piss-yellow mess.
4) Using a fairly fine utensil (I used popsicle stick broken in half lengthwise)put a good size dollop inside the lower receiver channel as far back as you can. Close the received on the gauges making sure they are far enough forward to not get stuck.
Once you close it, don't move it at all, if you think it is not tight enough, don't try to move the gauges forward to change the fit, the glas won't follow.
6) After the prescribed length of time remove the pin and open the receiver. At ~24 hours the glas hasn't set, but is hard enough to work with and will hold its shape. Taking a sharp chisel you can shave the hunk down to clean up the sides and get all your corners square and flat. Purely for looks at this point, for the OCD in us all.
Following those steps, you will effectively remove all play from the two halves and make the connection like a rock (if you did it right), it may actually take a week or so of work to work out some of the excess tightness.
Good thing about the gel, if you screw it up and lock both halves together, you can heat the whole thing in an oven and the bond will break.
Your sights and barrel are not exactly parallel, that is very common, and can be caused by a number of things. A short list from the very top of my head...
Sight base slightly off alignment with threads, spring pressure for the ball bearing in the front of the sight base wrong/missing, front sight base angled slightly, front ring of receiver not true, barrel trunion not true, piece of grit in between the trunion/receiver, crown cut at an angle (I've seen some terrible factory crowns), flash suppressor/threads angled or ports on the left side are closed somehow, hole in flash suppressor not centered with threads, chamber/chamber throat not indexed at start of cutting putting bullet into bore wrong, extreme curve in the bore (meaning, from where the chamber is cut, the barrel will curve over to the side and then back the other way resulting in an arc. I've not seen this in newer stuff, I think modern machining practices improve consistency greatly.)
By no means complete, but just move your sights over to the side and set your zero. Don't forget to make a mark so you know exactly where your zero is if you have to adjust windage at any time.
4/19/2012 8:49:03 AM
What sights do you have on the rifle? Who assembled the rifle?
I went through this with a 16" flat-top upper that my son bought from Del-Ton way back right after Obama got elected and the panic buying was on. It shot 28 MOA right and low, or about 7" at 25 yards. The first thing we did was try canting the barrel a little so as to tilt the FSB. We did so by filing the notch that the barrel extension pin fits in a little to one side. After doing so, neither of us were happy with that solution.
Eventually we bought a new stripped upper and switched all of the parts over. But before we put it together I bought a Receiver Lapping Tool from Brownells ( http://www.brownells.com/.aspx/pid=20220/Product/AR-15-M16-UPPER-RECEIVER-LAPPING-TOOL ), picked up a tube of valve grinding compound from Auto Zone, and used that to "true" the front of the new receiver. What I think happens is, when they machine the receiver, they have to use a threading die to cut the threads on the "nipple" where the barrel nut threads on. The shoulder on the barrel extension seats against the front of this "nipple", which determines how straight the barrel goes on relative to the receiver. I believe that when the threading die starts to "bite" into the soft aluminum of the receiver, the threading die "stretches" aluminum forward right at the point where the threads start. This makes the face of the receiver that the barrel extension seats against not perpendicular to the bore of the barrel, hence the barrel mounts a little crooked.
When I used the Brownells tool on the new receiver, I turned it by hand (I did not chuck it into a drill as they say you can on the principal that I can always take more metal off, but it's hard to put it back on.) and stopped frequently to wipe off the grinding compound and check my progress. It was obvious that the tool started removing material from one portion of the face of the receiver first, which meant that the face was not, as I expected, square to the receiver. I just continued using the tool on it until I had evidence of good contact around 80% to 90% of the circumference of the receiver face.
After we got the rifle back together it only needed a couple clicks of windage to zero.
I recently bought an M4 rifle kit from J&T distributing. I was please to see that it zeroed perfectly for windage, and that I (using a RIBZ 50-yard zero) only had to change the front sight post to an .040" taller one to get elevation zero. I currently have a "removable carry handle" rear sight on it that also came from J&T. I also checked it with one of those laser bore sighting gizmos that are built into a cartridge case that fits into the chamber - the laser showed it to be a few clicks off, but when I shot it with the rear sight at mechanical zero it was right on.
Hope this gives you some ideas.
I went through this with a 16" flat-top upper that my son bought from Del-Ton way back right after Obama got elected and the panic buying was on. It shot 28 MOA right and low, or about 7" at 25 yards. The first thing we did was try canting the barrel a little so as to tilt the FSB. We did so by filing the notch that the barrel extension pin fits in a little to one side. After doing so, neither of us were happy with that solution.
Eventually we bought a new stripped upper and switched all of the parts over. But before we put it together I bought a Receiver Lapping Tool from Brownells ( http://www.brownells.com/.aspx/pid=20220/Product/AR-15-M16-UPPER-RECEIVER-LAPPING-TOOL ), picked up a tube of valve grinding compound from Auto Zone, and used that to "true" the front of the new receiver. What I think happens is, when they machine the receiver, they have to use a threading die to cut the threads on the "nipple" where the barrel nut threads on. The shoulder on the barrel extension seats against the front of this "nipple", which determines how straight the barrel goes on relative to the receiver. I believe that when the threading die starts to "bite" into the soft aluminum of the receiver, the threading die "stretches" aluminum forward right at the point where the threads start. This makes the face of the receiver that the barrel extension seats against not perpendicular to the bore of the barrel, hence the barrel mounts a little crooked.
When I used the Brownells tool on the new receiver, I turned it by hand (I did not chuck it into a drill as they say you can on the principal that I can always take more metal off, but it's hard to put it back on.) and stopped frequently to wipe off the grinding compound and check my progress. It was obvious that the tool started removing material from one portion of the face of the receiver first, which meant that the face was not, as I expected, square to the receiver. I just continued using the tool on it until I had evidence of good contact around 80% to 90% of the circumference of the receiver face.
After we got the rifle back together it only needed a couple clicks of windage to zero.
I recently bought an M4 rifle kit from J&T distributing. I was please to see that it zeroed perfectly for windage, and that I (using a RIBZ 50-yard zero) only had to change the front sight post to an .040" taller one to get elevation zero. I currently have a "removable carry handle" rear sight on it that also came from J&T. I also checked it with one of those laser bore sighting gizmos that are built into a cartridge case that fits into the chamber - the laser showed it to be a few clicks off, but when I shot it with the rear sight at mechanical zero it was right on.
Hope this gives you some ideas.
