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Posted: 9/4/2009 12:53:09 PM EDT
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http://yfrog.com/e0fssidejx
Hello, Can't seem to figure out how to post pics so here is a link. http://yfrog.com/e0fssidejx The problem: I bought this used flat top AR15 upper assembly and was told it was an Armalite. When I tried zeroing this rifle at 25 meters with the rear sight at it's lowest position, and using the unmarked aperture, it shot very high and to reach point of aim the front post had to be raised until the front post flange was approx. 0.200 in above where it was flush with the front sight base (see attached pic), . The facts: The detachable carry handle windage knob is marked Armalite (see attached pic) ,it has knurled thumb screws ,the elevation knob is marked 0-20, (see attached pic) The front sight base with no bayonet lug is marked "? 2 II" on the side (see attached pic) and is attached with allen screws ,not pinned. the sight pin is approx .275 high. The 20" barrel has a threaded end. The receiver has knight system markings, small pin, standard feed ramps, and has the sear relief. There are no other markings on this upper or barrel. My questions are: Are there different height i.e. shorter carry handles that would lower my point of aim (this one measures approx. 1.3 in from receiver top to the top of the rear sight base? Should the rear sight base be canted this far (see attached pic)? Can you tell if this is an Armalite upper? Thanks for any help Eric |
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No attached pic.
Is the front post higher than the ears? My 16" non F marked front sight base had to be jacked up to almost flush with the ears on the front sight. I could see daylight under the "flange" so I ordered an extended front sight post and cured the problem. My "flange" still is higher than the base, but I cannot see daylight underneath it any more. |
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OK, out the gate, you going to need to pull the barrel.
Even without a F FSB, the front post is still way too tall at zero to solve with just a longer front sight post. With the FSB is set screw installed,pulling it off to check the straightness of the barrel is not going to be a problem. Start with the barrel alone, and roll it on a flat to see if it has been bent or warped. If you have a lathe, chuck it up and run a dial down it. From there, take a good look at the upper receiver barrel socket to confirm that is has not been warped or bend as well (true with the upper receiver bore line. If the two check out fine (guessing they won't), then install the barrel back on the receiver with the barrel nut hand tight, and start taking measurement of the barrel down the center line of the upper receiver (off the top rail will work). You are making sure that the barrel is true with the upper receiver rail flat, and not canting upwards in this case. If needed (again) barrel not bent, you may need to true the upper receiver socket so the barrel does install in the socket true to the center line. Once you have the barrel running true with the upper receiver, then the problem of not having a F FSB can be installed by just installing a FSB sight post that is .040 longer/higher. Bottom line here, if you have the option of sending the upper back for a refund, it may be your best option is you are not tooled up to correct the problem. |
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Quoted:
The problem: I bought this used flat top AR15 upper assembly and was told it was an Armalite. I think I would be talking to the seller to find out the real story on this. I'm sure you picked up the scent by now, but it sounds like you bought somebody else's headache. The preceding suggestions are excellent, assuming you want to make that sort of investment of your time and money in this sort of thing. |
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Sounds like I have two options. Buy a new upper assembly and use this old one for a tomato stake, or find someone that knows what they're doing to fix it. Any idea who to send it to and what kind of money we're talking? Can barrels be straightened?
The co-worker I bought this from was transfered out of state so refund is no go. |
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Quoted:
Sounds like I have two options. Buy a new upper assembly and use this old one for a tomato stake, or find someone that knows what they're doing to fix it. Any idea who to send it to and what kind of money we're talking? Can barrels be straightened? The co-worker I bought this from was transfered out of state so refund is no go. I'd just sell that thing on Gunbroker - WITH FULL DISCLOSURE - and chalk it up to lesson-learned. DSA is selling carbine uppers for $275. |
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First off. Welcome
Don't jump into selling, taking it apart or going off half cocked. I think you may have a carry handle designed for a carbine. Measure the height just behind the windage drum. If it's about .833" it's for a carbine a rifle should be about .794". As far as the markings on the drum and knob. Got no idea. I've got one as well. I used paint at the desired settings 458 |
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Quoted:
I think you may have a carry handle designed for a carbine. Measure the height just behind the windage drum. If it's about .833" it's for a carbine a rifle should be about .794". As far as the markings on the drum and knob. Got no idea. I've got one as well. I used paint at the desired settings 458 That's an excellent question. But, even assuming that is the case, how does the math work? If the rear sight is merely 0.040" too high, how would that account for the front sight needing to be 0.300" too high in order to regulate the existing sights to point of impact? The correction for a 0.040" error at the rear sight should only be 0.040" at the front sight. Based on the OP's facts, the present front sight correction is SEVEN TIMES the amount that the math associated with an incorrect carry handle would dictate. |
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It's not a question. Grasshopper.
The math can be found in any basic gunsmithing guide, on iron sights. I'll give you a clue. The barrel does not look at the same area as you do. Nor does the camera see what your eye see's. Or it may be just a FUP from the Mfg. Start with the basics 458 |
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It's not a question. Grasshopper. The math can be found in any basic gunsmithing guide, on iron sights. I'll give you a clue. The barrel does not look at the same area as you do. Nor does the camera see what your eye see's. Or it may be just a FUP from the Mfg. Start with the basics 458 You need a better explanation than that grasshopper. |
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Guys, enough banter since the point is mute over if the other parts are correct or not, since the issue is the barrel bore line not being parallel down the upper receiver!
The problem goes back to the height that he had to crank the front sight post up to zero the rifle, meaning that the barrel muzzle is pointing too skyward against the upper receiver to begin with. A few thousands (such as even around .040's) either in front post or rear sight base height is not going to do a bit of good to correct the over all problem stated above. If getting a refund from the seller is not in not going to happen, then the moneys that would be lost selling such with full discloser (the only correct way to sell such again, and the way it should have been sold in the first place), then pull the upper apart and start checking to see what is a miss. If you do not have such tooling/shop to start checking, then post in your Home town forum to see if other around you do. Bottom line, it's not the end of the world, and the problem can be resolved if the op just want to put in the labor. Here at the site, we go well beyond just parts swapping to bring things into tune, and his project is about on the par as they come. It could be as simple as the barrel not being seated correctly in the upper barrel socket causing the problem to begin with. Or worse, the barrel or upper socket bent, and these can be corrected with just a little more effect as well. All is not lost, but as stated from the beginning, the barrel needs to be pulled from the upper receiver to see where the problem lies/where the corrections need to begin. 
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That .040" height on a 20" sight radius equals about seven inches in elevation at 100 yards. To raise or lower just one in. only requires a change of .0055". (Marble's sight chart) Not all 'F' FSB are marked as such. A, F FSB is 1.98" tall from the top of barrel to it's shelf. Standard FSB is .040" shorter. Pesky number. I'd adjust that elevation drum to bottom out as shown in the RIBZ instructions and go from there. Eric can you put a scope on this thing and try that? This would take both sights out of the equation. And yes the rear sight cant is normal. 458 |
Front up .040 (new sight post), back down .040 (milled off the rear sight base shelf), or even the two combined for a .080 difference is not going to help in his case since this is where the front sight post is needed as of now to zero out the rifle (read way more than .080 if he did have the right height FSB and handle).
Regarding scoping the rig to bypass the sights, he may find a unit that will adjust this far out (upwards), or could mod the sight base or rings to do the same if the scope runs out of adjustment range. But even there, he would be band-aiding the problem by throwing more money at it, instead of just getting the barrel bore line back down the center line of the upper receiver (as stated, could be that the barrel extension is not seated true in the upper barrel socket due to an edge bur or piece of debris between the barrel extension and upper receiver socket lip). My vote has been, and is to pull the barrel off the upper and start checking to see what is wrong. If he doesn't have the needed tools, I am betting that someone in his area does, and would be willing to lend a helping hand just needs to ask in his home town forum). |
Good call.
| First off thanks for all the very helpful input. I was hoping for a quick fix but obviously this rifle has some deeper issues that I won't be able to address for a while. I think my course of action will be to return to the range and double check my zero. If that is still messed up ,I'lll do as suggested and get on the hometown site and see if I can find some local help with removing the barrel and checking the barrel and reciever . I'll update my findings when possible. Thanks again!! |
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Don't waste you time putting more ammo down the rifle. Post and see if you can find someone to help you pull the barrel and check it out.
As stated, it may be as simple as the barrel not fully seated in the upper barrel socket due to a piece of debris, and once removed and the barrel reinstalled, you may be good to go. Truthfully, it only take a min or two to pull a barrel and reinstall a barrel, and you could spin the barrel down a flat at the same time to weed that out as well. Figure drive time as well, and this could all could be behind in in less than a hour. |
| Ok so I finally got back to this project and I went to remove the muzzle brake. It broke loose and will easily go a 1/4 turn and then it tightens up again and won't go any further. This makes no sense. Normaly I would think heat but I can turn it the 1/4 turn by hand. Any ideas? |
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Quoted:
Ok so I finally got back to this project and I went to remove the muzzle brake. It broke loose and will easily go a 1/4 turn and then it tightens up again and won't go any further. This makes no sense. Normaly I would think heat but I can turn it the 1/4 turn by hand. Any ideas? Since it has a Brake instead of a FS, chances are the Brake is blind pinned to the barrel. Take a close look at the bottom of the break for a weld spot. If not found, then you may have to grind the bottom of the brake finish until you find the spot that was drilled through the brake and slightly into the barrel, a pin inserted, then the hole welded and finish back over. With the weld ground out, you should be able to remove the pin, and spin the brake off the barrel. |
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